#3756 Convert SearchDepictionsFragment to use Pagination (#3758)

app/build.gradle

@@ -45,6 +45,10 @@ dependencies {
     kapt "com.jakewharton:butterknife-compiler:$BUTTERKNIFE_VERSION"
     implementation "com.hannesdorfmann:adapterdelegates4-kotlin-dsl-layoutcontainer:$ADAPTER_DELEGATES_VERSION"
     implementation "com.hannesdorfmann:adapterdelegates4-pagination:$ADAPTER_DELEGATES_VERSION"
+    implementation "androidx.paging:paging-runtime-ktx:$PAGING_VERSION"
+    testImplementation "androidx.paging:paging-common-ktx:$PAGING_VERSION"
+    implementation "androidx.paging:paging-rxjava2-ktx:$PAGING_VERSION"
+    implementation "androidx.recyclerview:recyclerview:1.2.0-alpha02"
 
     // Logging
     implementation 'ch.acra:acra-dialog:5.3.0'

app/src/main/java/fr/free/nrw/commons/BasePresenter.java

@@ -1,5 +1,7 @@
 package fr.free.nrw.commons;
 
+import androidx.annotation.NonNull;
+
 /**
  * Base presenter, enforcing contracts to atach and detach view
  */
@@ -7,7 +9,7 @@ public interface BasePresenter<T> {
     /**
      * Until a view is attached, it is open to listen events from the presenter
      */
-    void onAttachView(T view);
+    void onAttachView(@NonNull T view);
 
     /**
      * Detaching a view makes sure that the view no more receives events from the presenter

app/src/main/java/fr/free/nrw/commons/depictions/subClass/SubDepictionAdapter.kt

@@ -0,0 +1,11 @@
+package fr.free.nrw.commons.depictions.subClass
+
+import fr.free.nrw.commons.explore.depictions.depictionDelegate
+import fr.free.nrw.commons.upload.categories.BaseDelegateAdapter
+import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+
+class SubDepictionAdapter(clickListener: (DepictedItem) -> Unit) :
+    BaseDelegateAdapter<DepictedItem>(
+        depictionDelegate(clickListener),
+        areItemsTheSame = { oldItem, newItem -> oldItem.id == newItem.id }
+    )

app/src/main/java/fr/free/nrw/commons/depictions/subClass/SubDepictionListContract.java

@@ -1,10 +1,9 @@
 package fr.free.nrw.commons.depictions.subClass;
 
-import java.io.IOException;
-import java.util.List;
-
 import fr.free.nrw.commons.BasePresenter;
 import fr.free.nrw.commons.upload.structure.depictions.DepictedItem;
+import java.io.IOException;
+import java.util.List;
 
 /**
  * The contract with which SubDepictionListFragment and its presenter would talk to each other
@@ -28,5 +27,6 @@ public interface SubDepictionListContract {
         void initSubDepictionList(String qid, Boolean isParentClass) throws IOException;
 
         String getQuery();
+
     }
 }

app/src/main/java/fr/free/nrw/commons/depictions/subClass/SubDepictionListFragment.java

@@ -20,7 +20,6 @@ import butterknife.ButterKnife;
 import dagger.android.support.DaggerFragment;
 import fr.free.nrw.commons.R;
 import fr.free.nrw.commons.depictions.WikidataItemDetailsActivity;
-import fr.free.nrw.commons.explore.depictions.DepictionAdapter;
 import fr.free.nrw.commons.upload.structure.depictions.DepictedItem;
 import fr.free.nrw.commons.utils.NetworkUtils;
 import fr.free.nrw.commons.utils.ViewUtil;
@@ -47,7 +46,7 @@ public class SubDepictionListFragment extends DaggerFragment implements SubDepic
      * Keeps a record of whether current instance of the fragment if of SubClass or ParentClass
      */
     private boolean isParentClass = false;
-    private DepictionAdapter depictionsAdapter;
+    private SubDepictionAdapter depictionsAdapter;
     RecyclerView.LayoutManager layoutManager;
     /**
      * Stores entityId for the depiction
@@ -100,7 +99,7 @@ public class SubDepictionListFragment extends DaggerFragment implements SubDepic
         }
         initViews();
         depictionsRecyclerView.setLayoutManager(layoutManager);
-        depictionsAdapter = new DepictionAdapter(depictedItem -> {
+        depictionsAdapter = new SubDepictionAdapter(depictedItem -> {
             // Open SubDepiction Details page
             getActivity().finish();
             WikidataItemDetailsActivity.startYourself(getContext(), depictedItem);

app/src/main/java/fr/free/nrw/commons/explore/SearchActivity.java

@@ -117,7 +117,7 @@ public class SearchActivity extends NavigationBaseActivity
                             searchHistoryContainer.setVisibility(View.GONE);
 
                             if (FragmentUtils.isFragmentUIActive(searchDepictionsFragment)) {
-                                searchDepictionsFragment.updateDepictionList(query.toString());
+                                searchDepictionsFragment.onQueryUpdated(query.toString());
                             }
 
                             if (FragmentUtils.isFragmentUIActive(searchImageFragment)) {

app/src/main/java/fr/free/nrw/commons/explore/SearchModule.java

@@ -2,6 +2,10 @@ package fr.free.nrw.commons.explore;
 
 import dagger.Binds;
 import dagger.Module;
+import dagger.Provides;
+import fr.free.nrw.commons.explore.depictions.DepictsClient;
+import fr.free.nrw.commons.explore.depictions.SearchDepictionsDataSourceFactory;
+import fr.free.nrw.commons.explore.depictions.SearchDepictionsDataSourceFactoryFactory;
 import fr.free.nrw.commons.explore.depictions.SearchDepictionsFragmentContract;
 import fr.free.nrw.commons.explore.depictions.SearchDepictionsFragmentPresenter;
 
@@ -16,4 +20,10 @@ public abstract class SearchModule {
             SearchDepictionsFragmentPresenter
                     presenter
     );
+
+    @Provides
+    static public SearchDepictionsDataSourceFactoryFactory providesSearchDepictionsFactoryFactory(
+        DepictsClient depictsClient){
+        return (query, loadingStates) -> new SearchDepictionsDataSourceFactory(depictsClient, query, loadingStates);
+    }
 }

app/src/main/java/fr/free/nrw/commons/explore/depictions/DepictionAdapter.kt

@@ -1,12 +1,47 @@
 package fr.free.nrw.commons.explore.depictions
 
-import fr.free.nrw.commons.upload.categories.BaseDelegateAdapter
+import android.view.View
+import android.view.ViewGroup
+import androidx.paging.PagedListAdapter
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.RecyclerView
+import fr.free.nrw.commons.R
 import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+import kotlinx.android.extensions.LayoutContainer
+import kotlinx.android.synthetic.main.item_depictions.*
 
 
-class DepictionAdapter(clickListener: (DepictedItem) -> Unit) : BaseDelegateAdapter<DepictedItem>(
+class DepictionAdapter(val onDepictionClicked: (DepictedItem) -> Unit) :
-    depictionDelegate(clickListener),
+    PagedListAdapter<DepictedItem, DepictedItemViewHolder>(
-    areItemsTheSame = { oldItem, newItem -> oldItem.id == newItem.id }
+        object : DiffUtil.ItemCallback<DepictedItem>() {
-)
+            override fun areItemsTheSame(oldItem: DepictedItem, newItem: DepictedItem) =
+                oldItem.id == newItem.id
 
+            override fun areContentsTheSame(oldItem: DepictedItem, newItem: DepictedItem) =
+                oldItem == newItem
 
+        }
+
+    ) {
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DepictedItemViewHolder {
+        return DepictedItemViewHolder(parent.inflate(R.layout.item_depictions))
+    }
+
+    override fun onBindViewHolder(holder: DepictedItemViewHolder, position: Int) {
+        holder.bind(getItem(position)!!, onDepictionClicked)
+    }
+}
+
+class DepictedItemViewHolder(override val containerView: View) :
+    RecyclerView.ViewHolder(containerView), LayoutContainer {
+    fun bind(item: DepictedItem, onDepictionClicked: (DepictedItem) -> Unit) {
+        containerView.setOnClickListener { onDepictionClicked(item) }
+        depicts_label.text = item.name
+        description.text = item.description
+        if (item.imageUrl?.isNotBlank() == true) {
+            depicts_image.setImageURI(item.imageUrl)
+        } else {
+            depicts_image.setActualImageResource(R.drawable.ic_wikidata_logo_24dp)
+        }
+    }
+}

app/src/main/java/fr/free/nrw/commons/explore/depictions/FooterAdapter.kt

@@ -0,0 +1,54 @@
+package fr.free.nrw.commons.explore.depictions
+
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.annotation.LayoutRes
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
+import androidx.recyclerview.widget.RecyclerView
+import fr.free.nrw.commons.R
+import kotlinx.android.extensions.LayoutContainer
+import kotlinx.android.synthetic.main.list_item_load_more.*
+
+class FooterAdapter(private val onRefreshClicked: () -> Unit) :
+    ListAdapter<FooterItem, FooterViewHolder>(object :
+        DiffUtil.ItemCallback<FooterItem>() {
+        override fun areItemsTheSame(oldItem: FooterItem, newItem: FooterItem) = oldItem == newItem
+
+        override fun areContentsTheSame(oldItem: FooterItem, newItem: FooterItem) =
+            oldItem == newItem
+    }) {
+
+    override fun getItemViewType(position: Int): Int {
+        return getItem(position).ordinal
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
+        when (FooterItem.values()[viewType]) {
+            FooterItem.LoadingItem -> LoadingViewHolder(parent.inflate(R.layout.list_item_progress))
+            FooterItem.RefreshItem -> RefreshViewHolder(
+                parent.inflate(R.layout.list_item_load_more),
+                onRefreshClicked
+            )
+        }
+
+    override fun onBindViewHolder(holder: FooterViewHolder, position: Int) {}
+}
+
+open class FooterViewHolder(override val containerView: View) :
+    RecyclerView.ViewHolder(containerView),
+    LayoutContainer
+
+class LoadingViewHolder(containerView: View) : FooterViewHolder(containerView)
+class RefreshViewHolder(containerView: View, onRefreshClicked: () -> Unit) :
+    FooterViewHolder(containerView) {
+    init {
+        listItemLoadMoreButton.setOnClickListener { onRefreshClicked() }
+    }
+}
+
+enum class FooterItem { LoadingItem, RefreshItem }
+
+fun ViewGroup.inflate(@LayoutRes layoutId: Int, attachToRoot: Boolean = false): View =
+    LayoutInflater.from(context).inflate(layoutId, this, attachToRoot)

app/src/main/java/fr/free/nrw/commons/explore/depictions/SearchDepictionsDataSource.kt

@@ -0,0 +1,63 @@
+package fr.free.nrw.commons.explore.depictions
+
+import androidx.paging.PositionalDataSource
+import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+import io.reactivex.Completable
+import io.reactivex.processors.PublishProcessor
+import io.reactivex.schedulers.Schedulers
+import timber.log.Timber
+
+
+data class SearchDepictionsDataSource constructor(
+    private val depictsClient: DepictsClient,
+    private val loadingStates: PublishProcessor<LoadingState>,
+    private val query: String
+) : PositionalDataSource<DepictedItem>() {
+
+    private var lastExecutedRequest: (() -> Boolean)? = null
+
+    override fun loadInitial(
+        params: LoadInitialParams,
+        callback: LoadInitialCallback<DepictedItem>
+    ) {
+        storeAndExecute {
+            loadingStates.offer(LoadingState.InitialLoad)
+            performWithTryCatch {
+                callback.onResult(
+                    getItems(query, params.requestedLoadSize, params.requestedStartPosition),
+                    params.requestedStartPosition
+                )
+            }
+        }
+    }
+
+    override fun loadRange(params: LoadRangeParams, callback: LoadRangeCallback<DepictedItem>) {
+        storeAndExecute {
+            loadingStates.offer(LoadingState.Loading)
+            performWithTryCatch {
+                callback.onResult(getItems(query, params.loadSize, params.startPosition))
+            }
+        }
+    }
+
+    fun retryFailedRequest() {
+        Completable.fromAction { lastExecutedRequest?.invoke() }
+            .subscribeOn(Schedulers.io())
+            .subscribe()
+    }
+
+    private fun getItems(query: String, limit: Int, offset: Int) =
+        depictsClient.searchForDepictions(query, limit, offset).blockingGet()
+
+    private fun storeAndExecute(function: () -> Boolean) {
+        function.also { lastExecutedRequest = it }.invoke()
+    }
+
+    private fun performWithTryCatch(function: () -> Unit) = try {
+        function.invoke()
+        loadingStates.offer(LoadingState.Complete)
+    } catch (e: Exception) {
+        Timber.e(e)
+        loadingStates.offer(LoadingState.Error)
+    }
+}

app/src/main/java/fr/free/nrw/commons/explore/depictions/SearchDepictionsFragment.java

@@ -1,200 +0,0 @@
-package fr.free.nrw.commons.explore.depictions;
-
-import static android.view.View.GONE;
-import static android.view.View.VISIBLE;
-import static fr.free.nrw.commons.explore.depictions.DepictionAdapterDelegatesKt.depictionDelegate;
-
-import android.content.Context;
-import android.content.res.Configuration;
-import android.os.Bundle;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.ProgressBar;
-import android.widget.TextView;
-import androidx.annotation.NonNull;
-import androidx.recyclerview.widget.DiffUtil.ItemCallback;
-import androidx.recyclerview.widget.GridLayoutManager;
-import androidx.recyclerview.widget.LinearLayoutManager;
-import androidx.recyclerview.widget.RecyclerView;
-import butterknife.BindView;
-import butterknife.ButterKnife;
-import com.hannesdorfmann.adapterdelegates4.AsyncListDifferDelegationAdapter;
-import fr.free.nrw.commons.R;
-import fr.free.nrw.commons.depictions.WikidataItemDetailsActivity;
-import fr.free.nrw.commons.di.CommonsDaggerSupportFragment;
-import fr.free.nrw.commons.upload.structure.depictions.DepictedItem;
-import fr.free.nrw.commons.utils.NetworkUtils;
-import fr.free.nrw.commons.utils.ViewUtil;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Locale;
-import javax.inject.Inject;
-import kotlin.Unit;
-
-/**
- * Display depictions in search fragment
- */
-public class SearchDepictionsFragment extends CommonsDaggerSupportFragment implements SearchDepictionsFragmentContract.View {
-
-    @BindView(R.id.imagesListBox)
-    RecyclerView depictionsRecyclerView;
-    @BindView(R.id.imageSearchInProgress)
-    ProgressBar progressBar;
-    @BindView(R.id.imagesNotFound)
-    TextView depictionNotFound;
-    @BindView(R.id.bottomProgressBar)
-    ProgressBar bottomProgressBar;
-    private RecyclerView.LayoutManager layoutManager;
-    private boolean isLoading = true;
-    private final int PAGE_SIZE = 25;
-    @Inject
-    SearchDepictionsFragmentPresenter presenter;
-    private DepictionAdapter depictionsAdapter;
-    private boolean isLastPage;
-
-    @Override
-    public View onCreateView(final LayoutInflater inflater, final ViewGroup container, final Bundle savedInstanceState) {
-        final View rootView = inflater.inflate(R.layout.fragment_browse_image, container, false);
-        ButterKnife.bind(this, rootView);
-        if (getActivity().getResources().getConfiguration().orientation
-                == Configuration.ORIENTATION_PORTRAIT) {
-            layoutManager = new LinearLayoutManager(getContext());
-        } else {
-            layoutManager = new GridLayoutManager(getContext(), 2);
-        }
-        depictionsRecyclerView.setLayoutManager(layoutManager);
-        depictionsAdapter = new DepictionAdapter(
-            depictedItem -> {
-                WikidataItemDetailsActivity.startYourself(getContext(), depictedItem);
-                presenter.saveQuery();
-                return Unit.INSTANCE;
-            });
-        depictionsRecyclerView.setAdapter(depictionsAdapter);
-        depictionsRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
-            @Override
-            public void onScrollStateChanged(final RecyclerView recyclerView, final int newState) {
-                super.onScrollStateChanged(recyclerView, newState);
-            }
-
-            @Override
-            public void onScrolled(@NonNull final RecyclerView recyclerView, final int dx, final int dy) {
-                super.onScrolled(recyclerView, dx, dy);
-
-                final int visibleItemCount = layoutManager.getChildCount();
-                final int totalItemCount = layoutManager.getItemCount();
-                int firstVisibleItemPosition=0;
-                if(layoutManager instanceof GridLayoutManager){
-                    firstVisibleItemPosition=((GridLayoutManager) layoutManager).findFirstVisibleItemPosition();
-                } else {
-                    firstVisibleItemPosition=((LinearLayoutManager)layoutManager).findFirstVisibleItemPosition();
-                }
-
-                /**
-                 * If the user isn't currently loading items and the last page hasn’t been reached,
-                 * then it checks against the current position in view to decide whether or not to load more items.
-                 */
-                if (!isLoading && !isLastPage) {
-                    if ((visibleItemCount + firstVisibleItemPosition) >= totalItemCount
-                            && firstVisibleItemPosition >= 0
-                            && totalItemCount >= PAGE_SIZE) {
-                        loadMoreItems(false);
-                    }
-                }
-            }
-        });
-        return rootView;
-    }
-
-    /**
-     * Fetch PAGE_SIZE number of items
-     */
-    private void loadMoreItems(final boolean reInitialise) {
-        presenter.updateDepictionList(presenter.getQuery(),PAGE_SIZE, reInitialise);
-    }
-
-    @Override
-    public void onAttach(final Context context) {
-        super.onAttach(context);
-        presenter.onAttachView(this);
-    }
-
-    /**
-     * Called when user selects "Items" from Search Activity
-     * to load the list of depictions from API
-     *
-     * @param query string searched in the Explore Activity
-     */
-    public void updateDepictionList(final String query) {
-        presenter.initializeQuery(query);
-         if (!NetworkUtils.isInternetConnectionEstablished(getContext())) {
-            handleNoInternet();
-            return;
-        }
-        loadMoreItems(true);
-    }
-
-    /**
-     * Handles the UI updates for a error scenario
-     */
-    @Override
-    public void initErrorView() {
-        isLoading = false;
-        progressBar.setVisibility(GONE);
-        bottomProgressBar.setVisibility(GONE);
-        depictionNotFound.setVisibility(VISIBLE);
-        final String no_depiction = getString(R.string.depictions_not_found);
-        depictionNotFound.setText(String.format(Locale.getDefault(), no_depiction, presenter.getQuery()));
-    }
-
-    /**
-     * Handles the UI updates for no internet scenario
-     */
-    @Override
-    public void handleNoInternet() {
-        progressBar.setVisibility(GONE);
-        ViewUtil.showShortSnackbar(depictionsRecyclerView, R.string.no_internet);
-    }
-
-    /**
-     * If a non empty list is successfully returned from the api then modify the view
-     * like hiding empty labels, hiding progressbar and notifying the apdapter that list of items has been fetched from the API
-     */
-    @Override
-    public void onSuccess(final List<DepictedItem> mediaList) {
-        isLoading = false;
-        progressBar.setVisibility(GONE);
-        depictionNotFound.setVisibility(GONE);
-        bottomProgressBar.setVisibility(GONE);
-        depictionsAdapter.addAll(mediaList);
-    }
-
-    @Override
-    public void loadingDepictions(final boolean isLoading) {
-        depictionNotFound.setVisibility(GONE);
-        bottomProgressBar.setVisibility(VISIBLE);
-        progressBar.setVisibility(GONE);
-        this.isLoading = isLoading;
-    }
-
-    @Override
-    public void clearAdapter() {
-        depictionsAdapter.clear();
-    }
-
-    @Override
-    public void showSnackbar() {
-        ViewUtil.showShortSnackbar(depictionsRecyclerView, R.string.error_loading_depictions);
-    }
-
-    /**
-     * Inform the view that there are no more items to be loaded for this search query
-     * or reset the isLastPage for the current query
-     * @param isLastPage
-     */
-    @Override
-    public void setIsLastPage(final boolean isLastPage) {
-        this.isLastPage=isLastPage;
-        progressBar.setVisibility(GONE);
-    }
-}

app/src/main/java/fr/free/nrw/commons/explore/depictions/SearchDepictionsFragment.kt

@@ -0,0 +1,99 @@
+package fr.free.nrw.commons.explore.depictions
+
+import android.content.Context
+import android.content.res.Configuration
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.View.GONE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import androidx.fragment.app.Fragment
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.Observer
+import androidx.paging.PagedList
+import androidx.recyclerview.widget.GridLayoutManager
+import androidx.recyclerview.widget.MergeAdapter
+import fr.free.nrw.commons.R
+import fr.free.nrw.commons.depictions.WikidataItemDetailsActivity
+import fr.free.nrw.commons.di.CommonsDaggerSupportFragment
+import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+import fr.free.nrw.commons.utils.ViewUtil
+import kotlinx.android.synthetic.main.fragment_search_depictions.*
+import javax.inject.Inject
+
+/**
+ * Display depictions in search fragment
+ */
+class SearchDepictionsFragment : CommonsDaggerSupportFragment(),
+    SearchDepictionsFragmentContract.View {
+
+    @Inject
+    lateinit var presenter: SearchDepictionsFragmentContract.UserActionListener
+
+    private val depictionsAdapter by lazy {
+        DepictionAdapter { WikidataItemDetailsActivity.startYourself(context, it) }
+    }
+    private val loadingAdapter by lazy { FooterAdapter { presenter.retryFailedRequest() } }
+    private val mergeAdapter by lazy { MergeAdapter(depictionsAdapter, loadingAdapter) }
+
+    var searchResults: LiveData<PagedList<DepictedItem>>? = null
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ) = inflater.inflate(R.layout.fragment_search_depictions, container, false)
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        depictionsSearchResultsList.apply {
+            layoutManager = GridLayoutManager(context, if (isPortrait) 1 else 2)
+            adapter = mergeAdapter
+        }
+        presenter.listFooterData.observe(viewLifecycleOwner, Observer(loadingAdapter::submitList))
+    }
+
+    override fun onAttach(context: Context) {
+        super.onAttach(context)
+        presenter.onAttachView(this)
+    }
+
+    override fun onDetach() {
+        super.onDetach()
+        presenter.onDetachView()
+    }
+
+    override fun observeSearchResults(searchResults: LiveData<PagedList<DepictedItem>>) {
+        this.searchResults?.removeObservers(viewLifecycleOwner)
+        this.searchResults = searchResults
+        searchResults.observe(viewLifecycleOwner, Observer {
+            depictionsAdapter.submitList(it)
+            depictionNotFound.visibility = if (it.loadedCount == 0) VISIBLE else GONE
+        })
+    }
+
+    override fun setEmptyViewText(query: String) {
+        depictionNotFound.text = getString(R.string.depictions_not_found, query)
+    }
+
+    override fun hideInitialLoadProgress() {
+        depictionSearchInitialLoadProgress.visibility = GONE
+    }
+
+    override fun showInitialLoadInProgress() {
+        depictionSearchInitialLoadProgress.visibility = VISIBLE
+    }
+
+    override fun showSnackbar() {
+        ViewUtil.showShortSnackbar(depictionsSearchResultsList, R.string.error_loading_depictions)
+    }
+
+    fun onQueryUpdated(query: String) {
+        presenter.onQueryUpdated(query)
+    }
+}
+
+private val Fragment.isPortrait get() = orientation == Configuration.ORIENTATION_PORTRAIT
+
+private val Fragment.orientation get() = activity!!.resources.configuration.orientation

app/src/main/java/fr/free/nrw/commons/explore/depictions/SearchDepictionsFragmentContract.java

@@ -1,79 +0,0 @@
-package fr.free.nrw.commons.explore.depictions;
-
-import fr.free.nrw.commons.BasePresenter;
-import fr.free.nrw.commons.upload.structure.depictions.DepictedItem;
-import java.util.List;
-
-/**
- * The contract with with SearchDepictionsFragment and its presenter would talk to each other
- */
-public interface SearchDepictionsFragmentContract {
-
-    interface View {
-        /**
-         * Handles the UI updates for a error scenario
-         */
-        void initErrorView();
-
-        /**
-         * Handles the UI updates for no internet scenario
-         */
-        void handleNoInternet();
-
-        /**
-         * If a non empty list is successfully returned from the api then modify the view
-         * like hiding empty labels, hiding progressbar and notifying the apdapter that list of items has been fetched from the API
-         */
-        void onSuccess(List<DepictedItem> mediaList);
-
-        /**
-         * load depictions
-         */
-        void loadingDepictions(boolean isLoading);
-
-        /**
-         * clear adapter
-         */
-        void clearAdapter();
-
-        /**
-         * show snackbar
-         */
-        void showSnackbar();
-
-        /**
-         * Inform the view that there are no more items to be loaded for this search query
-         * or reset the isLastPage for the current query
-         * @param isLastPage
-         */
-        void setIsLastPage(boolean isLastPage);
-    }
-
-    interface UserActionListener extends BasePresenter<View> {
-
-        /**
-         * Called when user selects "Items" from Search Activity
-         * to load the list of depictions from API
-         *
-         * @param query string searched in the Explore Activity
-         * @param reInitialise
-         */
-        void updateDepictionList(String query, int pageSize, boolean reInitialise);
-
-        /**
-         * This method saves Search Query in the Recent Searches Database.
-         */
-        void saveQuery();
-
-        /**
-         * Whenever a new query is initiated from the search activity clear the previous adapter
-         * and add new value of the query
-         */
-        void initializeQuery(String query);
-
-        /**
-         * @return query
-         */
-        String getQuery();
-    }
-}

app/src/main/java/fr/free/nrw/commons/explore/depictions/SearchDepictionsFragmentContract.kt

@@ -0,0 +1,25 @@
+package fr.free.nrw.commons.explore.depictions
+
+import androidx.lifecycle.LiveData
+import androidx.paging.PagedList
+import fr.free.nrw.commons.BasePresenter
+import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+
+/**
+ * The contract with with SearchDepictionsFragment and its presenter would talk to each other
+ */
+interface SearchDepictionsFragmentContract {
+    interface View {
+        fun showSnackbar()
+        fun observeSearchResults(searchResults: LiveData<PagedList<DepictedItem>>)
+        fun setEmptyViewText(query: String)
+        fun showInitialLoadInProgress()
+        fun hideInitialLoadProgress()
+    }
+
+    interface UserActionListener : BasePresenter<View?> {
+        val listFooterData: LiveData<List<FooterItem>>
+        fun onQueryUpdated(query: String)
+        fun retryFailedRequest()
+    }
+}

app/src/main/java/fr/free/nrw/commons/explore/depictions/SearchDepictionsFragmentPresenter.java

@@ -1,158 +0,0 @@
-package fr.free.nrw.commons.explore.depictions;
-
-import static fr.free.nrw.commons.di.CommonsApplicationModule.IO_THREAD;
-import static fr.free.nrw.commons.di.CommonsApplicationModule.MAIN_THREAD;
-
-import fr.free.nrw.commons.di.CommonsDaggerSupportFragment;
-import fr.free.nrw.commons.explore.recentsearches.RecentSearch;
-import fr.free.nrw.commons.explore.recentsearches.RecentSearchesDao;
-import fr.free.nrw.commons.kvstore.JsonKvStore;
-import fr.free.nrw.commons.upload.structure.depictions.DepictedItem;
-import io.reactivex.Scheduler;
-import io.reactivex.disposables.CompositeDisposable;
-import java.lang.reflect.Proxy;
-import java.util.ArrayList;
-import java.util.Date;
-import java.util.List;
-import javax.inject.Inject;
-import javax.inject.Named;
-import timber.log.Timber;
-
-/**
- * The presenter class for SearchDepictionsFragment
- */
-public class SearchDepictionsFragmentPresenter extends CommonsDaggerSupportFragment implements SearchDepictionsFragmentContract.UserActionListener {
-
-    /**
-     * This creates a dynamic proxy instance of the class,
-     * proxy is to control access to the target object
-     * here our target object is the view.
-     * Thus we when onDettach method of fragment is called we replace the binding of view to our object with the proxy instance
-     */
-    private static final SearchDepictionsFragmentContract.View DUMMY = (SearchDepictionsFragmentContract.View) Proxy
-            .newProxyInstance(
-                    SearchDepictionsFragmentContract.View.class.getClassLoader(),
-                    new Class[]{SearchDepictionsFragmentContract.View.class},
-                    (proxy, method, methodArgs) -> null);
-    protected CompositeDisposable compositeDisposable = new CompositeDisposable();
-    private final Scheduler ioScheduler;
-    private final Scheduler mainThreadScheduler;
-
-    boolean isLoadingDepictions;
-    String query;
-    RecentSearchesDao recentSearchesDao;
-    DepictsClient depictsClient;
-    JsonKvStore basicKvStore;
-    private SearchDepictionsFragmentContract.View view = DUMMY;
-    private List<DepictedItem> queryList = new ArrayList<>();
-    int offset=0;
-    int size = 0;
-
-    @Inject
-    public SearchDepictionsFragmentPresenter(@Named("default_preferences") JsonKvStore basicKvStore,
-                                             RecentSearchesDao recentSearchesDao,
-                                             DepictsClient depictsClient,
-                                             @Named(IO_THREAD) Scheduler ioScheduler,
-                                             @Named(MAIN_THREAD) Scheduler mainThreadScheduler) {
-        this.basicKvStore = basicKvStore;
-        this.recentSearchesDao = recentSearchesDao;
-        this.depictsClient = depictsClient;
-        this.ioScheduler = ioScheduler;
-        this.mainThreadScheduler = mainThreadScheduler;
-    }
-
-    @Override
-    public void onAttachView(SearchDepictionsFragmentContract.View view) {
-        this.view = view;
-    }
-
-    @Override
-    public void onDetachView() {
-        this.view = DUMMY;
-    }
-
-    /**
-     * Called when user selects "Items" from Search Activity
-     * to load the list of depictions from API
-     *
-     * @param query string searched in the Explore Activity
-     * @param reInitialise
-     */
-    @Override
-    public void updateDepictionList(String query, int pageSize, boolean reInitialise) {
-      this.query = query;
-      view.loadingDepictions(true);
-      if (reInitialise) {
-        size = 0;
-      }
-      saveQuery();
-      compositeDisposable.add(depictsClient.searchForDepictions(query, 25, offset)
-            .subscribeOn(ioScheduler)
-            .observeOn(mainThreadScheduler)
-            .doOnSubscribe(disposable -> saveQuery())
-            .subscribe(this::handleSuccess, this::handleError));
-    }
-
-    /**
-     * Logs and handles API error scenario
-     */
-    private void handleError(Throwable throwable) {
-        Timber.e(throwable, "Error occurred while loading queried depictions");
-        view.initErrorView();
-        view.showSnackbar();
-    }
-
-    /**
-     * This method saves Search Query in the Recent Searches Database.
-     */
-    @Override
-    public void saveQuery() {
-        RecentSearch recentSearch = recentSearchesDao.find(query);
-
-        // Newly searched query...
-        if (recentSearch == null) {
-            recentSearch = new RecentSearch(null, query, new Date());
-        } else {
-            recentSearch.setLastSearched(new Date());
-        }
-        recentSearchesDao.save(recentSearch);
-
-    }
-
-    /**
-     * Whenever a new query is initiated from the search activity clear the previous adapter
-     * and add new value of the query
-     */
-    @Override
-    public void initializeQuery(String query) {
-        this.query = query;
-        this.queryList.clear();
-        offset = 0;//Reset the offset on query change
-        compositeDisposable.clear();
-        view.setIsLastPage(false);
-        view.clearAdapter();
-    }
-
-    @Override
-    public String getQuery() {
-        return query;
-    }
-
-    /**
-     * Handles the success scenario
-     * it initializes the recycler view by adding items to the adapter
-     */
-    public void handleSuccess(List<DepictedItem> mediaList) {
-        if (mediaList == null || mediaList.isEmpty()) {
-            if(queryList.isEmpty()){
-                view.initErrorView();
-            }else{
-                view.setIsLastPage(true);
-            }
-        } else {
-            this.queryList.addAll(mediaList);
-            view.onSuccess(mediaList);
-            offset=queryList.size();
-        }
-    }
-}

app/src/main/java/fr/free/nrw/commons/explore/depictions/SearchDepictionsFragmentPresenter.kt

@@ -0,0 +1,73 @@
+package fr.free.nrw.commons.explore.depictions
+
+import androidx.lifecycle.MutableLiveData
+import fr.free.nrw.commons.di.CommonsApplicationModule
+import fr.free.nrw.commons.upload.depicts.proxy
+import io.reactivex.Scheduler
+import io.reactivex.disposables.CompositeDisposable
+import timber.log.Timber
+import javax.inject.Inject
+import javax.inject.Named
+
+/**
+ * The presenter class for SearchDepictionsFragment
+ */
+class SearchDepictionsFragmentPresenter @Inject constructor(
+    @param:Named(CommonsApplicationModule.MAIN_THREAD) private val mainThreadScheduler: Scheduler,
+    private val searchableDataSourceFactory: SearchableDepictionsDataSourceFactory
+) : SearchDepictionsFragmentContract.UserActionListener {
+    private val compositeDisposable = CompositeDisposable()
+    private var view = DUMMY
+    private var currentQuery: String? = null
+    override val listFooterData = MutableLiveData<List<FooterItem>>().apply { value = emptyList() }
+
+    override fun onAttachView(view: SearchDepictionsFragmentContract.View) {
+        this.view = view
+        compositeDisposable.addAll(
+            searchableDataSourceFactory.searchResults.subscribe(view::observeSearchResults),
+            searchableDataSourceFactory.loadingStates
+                .observeOn(mainThreadScheduler)
+                .subscribe(::onLoadingState, Timber::e),
+            searchableDataSourceFactory.noItemsLoadedEvent.subscribe {
+                setEmptyViewText()
+            }
+        )
+    }
+
+    private fun onLoadingState(it: LoadingState) = when (it) {
+        LoadingState.Loading -> listFooterData.postValue(listOf(FooterItem.LoadingItem))
+        LoadingState.Complete -> {
+            listFooterData.postValue(emptyList())
+            view.hideInitialLoadProgress()
+        }
+        LoadingState.InitialLoad -> view.showInitialLoadInProgress()
+        LoadingState.Error -> {
+            setEmptyViewText()
+            view.showSnackbar()
+            view.hideInitialLoadProgress()
+            listFooterData.postValue(listOf(FooterItem.RefreshItem))
+        }
+    }
+
+    private fun setEmptyViewText() {
+        currentQuery?.let(view::setEmptyViewText)
+    }
+
+    override fun retryFailedRequest() {
+        searchableDataSourceFactory.retryFailedRequest()
+    }
+
+    override fun onDetachView() {
+        view = DUMMY
+        compositeDisposable.clear()
+    }
+
+    override fun onQueryUpdated(query: String) {
+        currentQuery = query
+        searchableDataSourceFactory.onQueryUpdated(query)
+    }
+
+    companion object {
+        private val DUMMY: SearchDepictionsFragmentContract.View = proxy()
+    }
+}

app/src/main/java/fr/free/nrw/commons/explore/depictions/SearchableDepictionsDataSourceFactory.kt

@@ -0,0 +1,88 @@
+package fr.free.nrw.commons.explore.depictions
+
+import androidx.lifecycle.LiveData
+import androidx.paging.Config
+import androidx.paging.DataSource
+import androidx.paging.PagedList
+import androidx.paging.toLiveData
+import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+import io.reactivex.Flowable
+import io.reactivex.processors.PublishProcessor
+import javax.inject.Inject
+
+private const val PAGE_SIZE = 50
+private const val INITIAL_LOAD_SIZE = 50
+
+class SearchableDepictionsDataSourceFactory @Inject constructor(
+    val searchDepictionsDataSourceFactoryFactory: SearchDepictionsDataSourceFactoryFactory,
+    val liveDataConverter: LiveDataConverter
+) {
+    private val _loadingStates = PublishProcessor.create<LoadingState>()
+    val loadingStates: Flowable<LoadingState> = _loadingStates
+    private val _searchResults = PublishProcessor.create<LiveData<PagedList<DepictedItem>>>()
+    val searchResults: Flowable<LiveData<PagedList<DepictedItem>>> = _searchResults
+    private val _noItemsLoadedEvent = PublishProcessor.create<Unit>()
+    val noItemsLoadedEvent: Flowable<Unit> = _noItemsLoadedEvent
+
+    private var currentFactory: SearchDepictionsDataSourceFactory? = null
+
+    fun onQueryUpdated(query: String) {
+        _searchResults.offer(
+            liveDataConverter.convert(
+                searchDepictionsDataSourceFactoryFactory.create(query, _loadingStates)
+                    .also { currentFactory = it }
+            ) { _noItemsLoadedEvent.offer(Unit) }
+        )
+    }
+
+    fun retryFailedRequest() {
+        currentFactory?.retryFailedRequest()
+    }
+}
+
+class LiveDataConverter @Inject constructor() {
+    fun convert(
+        dataSourceFactory: SearchDepictionsDataSourceFactory,
+        zeroItemsLoadedFunction: () -> Unit
+    ): LiveData<PagedList<DepictedItem>> {
+        return dataSourceFactory.toLiveData(
+            Config(
+                pageSize = PAGE_SIZE,
+                initialLoadSizeHint = INITIAL_LOAD_SIZE,
+                enablePlaceholders = false
+            ),
+            boundaryCallback = object : PagedList.BoundaryCallback<DepictedItem>() {
+                override fun onZeroItemsLoaded() {
+                    zeroItemsLoadedFunction()
+                }
+            }
+        )
+    }
+
+}
+
+interface SearchDepictionsDataSourceFactoryFactory {
+    fun create(query: String, loadingStates: PublishProcessor<LoadingState>)
+            : SearchDepictionsDataSourceFactory
+}
+
+class SearchDepictionsDataSourceFactory constructor(
+    private val depictsClient: DepictsClient,
+    private val query: String,
+    private val loadingStates: PublishProcessor<LoadingState>
+) : DataSource.Factory<Int, DepictedItem>() {
+    private var currentDataSource: SearchDepictionsDataSource? = null
+    override fun create() = SearchDepictionsDataSource(depictsClient, loadingStates, query)
+        .also { currentDataSource = it }
+
+    fun retryFailedRequest() {
+        currentDataSource?.retryFailedRequest()
+    }
+}
+
+sealed class LoadingState {
+    object InitialLoad : LoadingState()
+    object Loading : LoadingState()
+    object Complete : LoadingState()
+    object Error : LoadingState()
+}

app/src/main/java/fr/free/nrw/commons/upload/depicts/DepictsPresenter.kt

@@ -109,5 +109,11 @@ class DepictsPresenter @Inject constructor(
     }
 }
 
+/**
+ * This creates a dynamic proxy instance of the class,
+ * proxy is to control access to the target object
+ * here our target object is the view.
+ * Thus we when onDettach method of fragment is called we replace the binding of view to our object with the proxy instance
+ */
 inline fun <reified T> proxy() = Proxy
     .newProxyInstance(T::class.java.classLoader, arrayOf(T::class.java)) { _, _, _ -> null } as T

app/src/main/res/layout/fragment_search_depictions.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+  android:layout_width="match_parent"
+  android:layout_height="match_parent"
+  android:paddingTop="@dimen/tiny_gap"
+  android:orientation="vertical">
+
+  <TextView
+    android:id="@+id/depictionNotFound"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:layout_centerInParent="true"
+    android:gravity="center"
+    android:visibility="gone" />
+
+  <androidx.recyclerview.widget.RecyclerView
+    android:id="@+id/depictionsSearchResultsList"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:scrollbarSize="@dimen/standard_gap"
+    android:scrollbars="vertical" />
+
+  <ProgressBar
+    android:id="@+id/depictionSearchInitialLoadProgress"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:layout_centerInParent="true"/>
+
+</RelativeLayout>

app/src/main/res/layout/item_depictions.xml

@@ -1,37 +1,43 @@
 <?xml version="1.0" encoding="utf-8"?>
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
+  xmlns:app="http://schemas.android.com/apk/res-auto"
-    android:orientation="vertical" android:layout_width="match_parent"
+  xmlns:tools="http://schemas.android.com/tools"
+  android:layout_width="match_parent"
+  android:layout_height="wrap_content"
+  android:padding="@dimen/tiny_gap">
+
+  <TextView
+    android:id="@+id/depicts_label"
+    android:textStyle="bold"
+    android:layout_width="0dp"
     android:layout_height="wrap_content"
-    android:padding="@dimen/tiny_gap">
+    android:paddingTop="@dimen/tiny_gap"
+    android:text="Label"
+    android:textAppearance="?android:attr/textAppearanceMedium"
+    app:layout_constraintEnd_toEndOf="parent"
+    app:layout_constraintStart_toEndOf="@+id/depicts_image"
+    app:layout_constraintTop_toTopOf="parent"
+    tools:text="Really really really really long long long label" />
 
-    <com.facebook.drawee.view.SimpleDraweeView
+  <TextView
-        android:id="@+id/depicts_image"
+    android:id="@+id/description"
-        android:layout_width="70dp"
+    android:layout_width="0dp"
-        android:layout_height="70dp"
+    android:layout_height="wrap_content"
-        android:paddingRight="@dimen/tiny_gap"
+    android:paddingTop="@dimen/tiny_gap"
-        app:placeholderImage="@drawable/ic_wikidata_logo_24dp"
+    android:text="Description"
-        app:layout_constraintLeft_toLeftOf="parent"
+    tools:text="Really really really really long long long description description description"
-        app:layout_constraintTop_toTopOf="parent"/>
+    app:layout_constraintStart_toEndOf="@+id/depicts_image"
+    app:layout_constraintEnd_toEndOf="parent"
+    app:layout_constraintTop_toBottomOf="@+id/depicts_label" />
 
-    <TextView
+  <com.facebook.drawee.view.SimpleDraweeView
-        android:id="@+id/depicts_label"
+    android:id="@+id/depicts_image"
-        android:layout_width="wrap_content"
+    android:layout_width="70dp"
-        android:layout_height="wrap_content"
+    android:layout_height="70dp"
-        android:text="Label"
+    android:paddingRight="@dimen/tiny_gap"
-        android:textAppearance="?android:attr/textAppearanceMedium"
+    app:layout_constraintStart_toStartOf="parent"
-        android:textStyle="bold"
+    app:layout_constraintTop_toTopOf="parent"
-        android:paddingTop="@dimen/tiny_gap"
+    app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintLeft_toRightOf="@+id/depicts_image"
+    app:placeholderImage="@drawable/ic_wikidata_logo_24dp" />
-        app:layout_constraintTop_toTopOf="parent" />
-
-    <TextView
-        android:id="@+id/description"
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:text="Description"
-        android:paddingTop="@dimen/tiny_gap"
-        app:layout_constraintLeft_toRightOf="@+id/depicts_image"
-        app:layout_constraintTop_toBottomOf="@+id/depicts_label" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/list_item_load_more.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+  xmlns:app="http://schemas.android.com/apk/res-auto"
+  android:layout_width="match_parent"
+  android:layout_height="wrap_content"
+  android:padding="@dimen/small_gap">
+  <Button
+    android:id="@+id/listItemLoadMoreButton"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:text="@string/load_more"
+    android:textColor="@color/white"
+    app:layout_constraintBottom_toBottomOf="parent"
+    app:layout_constraintEnd_toEndOf="parent"
+    app:layout_constraintStart_toStartOf="parent"
+    app:layout_constraintTop_toTopOf="parent" />
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/list_item_progress.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+  xmlns:app="http://schemas.android.com/apk/res-auto"
+  android:layout_width="match_parent"
+  android:layout_height="wrap_content">
+  <ProgressBar
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    app:layout_constraintBottom_toBottomOf="parent"
+    app:layout_constraintEnd_toEndOf="parent"
+    app:layout_constraintStart_toStartOf="parent"
+    app:layout_constraintTop_toTopOf="parent" />
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/values/strings.xml

@@ -628,6 +628,6 @@ Upload your first media by tapping on the add button.</string>
   <string name="ask_to_turn_location_on">Turn on location?</string>
   <string name="nearby_needs_location">Nearby needs location enabled to work properly</string>
   <string name="use_location_from_similar_image">Did you shoot these two pictures at the same place? Do you want to use the latitude/longitude of the picture on the right?</string>
+  <string name="load_more">Load More</string>
   <string name="nearby_no_results">No places found, try changing your search criteria.</string>
-
 </resources>

app/src/test/kotlin/fr/free/nrw/commons/campaigns/CampaignsPresenterTest.kt

@@ -15,19 +15,19 @@ import kotlin.collections.ArrayList
 
 class CampaignsPresenterTest {
     @Mock
-    var okHttpJsonApiClient: OkHttpJsonApiClient? = null
+    lateinit var okHttpJsonApiClient: OkHttpJsonApiClient
 
     lateinit var campaignsPresenter: CampaignsPresenter
 
     @Mock
-    internal var view: ICampaignsView? = null
+    internal lateinit var view: ICampaignsView
 
     @Mock
-    internal var campaignResponseDTO: CampaignResponseDTO? = null
+    internal lateinit var campaignResponseDTO: CampaignResponseDTO
     lateinit var campaignsSingle: Single<CampaignResponseDTO>
 
     @Mock
-    var campaign: Campaign? = null
+    lateinit var campaign: Campaign
 
     lateinit var testScheduler: TestScheduler
 
@@ -41,37 +41,37 @@ class CampaignsPresenterTest {
         testScheduler=TestScheduler()
         campaignsSingle= Single.just(campaignResponseDTO)
         campaignsPresenter= CampaignsPresenter(okHttpJsonApiClient,testScheduler,testScheduler)
-        campaignsPresenter?.onAttachView(view)
+        campaignsPresenter.onAttachView(view)
-        Mockito.`when`(okHttpJsonApiClient?.campaigns).thenReturn(campaignsSingle)
+        Mockito.`when`(okHttpJsonApiClient.campaigns).thenReturn(campaignsSingle)
     }
 
     @Test
     fun getCampaignsTestNoCampaigns() {
         campaignsPresenter.getCampaigns()
-        verify(okHttpJsonApiClient)?.campaigns
+        verify(okHttpJsonApiClient).campaigns
         testScheduler.triggerActions()
-        verify(view)?.showCampaigns(null)
+        verify(view).showCampaigns(null)
     }
 
     @Test
     fun getCampaignsTestNonEmptyCampaigns() {
         campaignsPresenter.getCampaigns()
         var campaigns= ArrayList<Campaign>()
-        campaigns.add(campaign!!)
+        campaigns.add(campaign)
         val simpleDateFormat = SimpleDateFormat("yyyy-MM-dd", Locale.ROOT)
         simpleDateFormat.timeZone = TimeZone.getTimeZone("UTC")
-        Mockito.`when`(campaignResponseDTO?.campaigns).thenReturn(campaigns)
+        Mockito.`when`(campaignResponseDTO.campaigns).thenReturn(campaigns)
         var calendar = Calendar.getInstance()
         calendar.add(Calendar.DATE,-1)
         val startDateString = simpleDateFormat.format(calendar.time).toString()
         calendar= Calendar.getInstance()
         calendar.add(Calendar.DATE,3)
         val endDateString= simpleDateFormat.format(calendar.time).toString()
-        Mockito.`when`(campaign?.endDate).thenReturn(endDateString)
+        Mockito.`when`(campaign.endDate).thenReturn(endDateString)
-        Mockito.`when`(campaign?.startDate).thenReturn(startDateString)
+        Mockito.`when`(campaign.startDate).thenReturn(startDateString)
-        Mockito.`when`(campaignResponseDTO?.campaigns).thenReturn(campaigns)
+        Mockito.`when`(campaignResponseDTO.campaigns).thenReturn(campaigns)
-        verify(okHttpJsonApiClient)?.campaigns
+        verify(okHttpJsonApiClient).campaigns
         testScheduler.triggerActions()
-        verify(view)?.showCampaigns(campaign)
+        verify(view).showCampaigns(campaign)
     }
 }

app/src/test/kotlin/fr/free/nrw/commons/depictions/DepictedImagesPresenterTest.kt

@@ -1,6 +1,5 @@
 package fr.free.nrw.commons.depictions
 
-import org.mockito.Mockito.verify
 import fr.free.nrw.commons.Media
 import fr.free.nrw.commons.depictions.Media.DepictedImagesFragment
 import fr.free.nrw.commons.depictions.Media.DepictedImagesPresenter
@@ -15,24 +14,26 @@ import org.junit.Test
 import org.mockito.ArgumentMatchers
 import org.mockito.Mock
 import org.mockito.Mockito
+import org.mockito.Mockito.verify
 import org.mockito.MockitoAnnotations
 
 class DepictedImagesPresenterTest {
 
     @Mock
-    internal var view: DepictedImagesFragment? = null
+    internal lateinit var view: DepictedImagesFragment
 
-    var depictedImagesPresenter: DepictedImagesPresenter? = null
+    lateinit var depictedImagesPresenter: DepictedImagesPresenter
-
-    var jsonKvStore: JsonKvStore? = null
 
     @Mock
-    var depictsClient: DepictsClient? = null
+    lateinit var jsonKvStore: JsonKvStore
 
     @Mock
-    var mediaClient: MediaClient? = null
+    lateinit var depictsClient: DepictsClient
 
-    var testScheduler: TestScheduler? = null
+    @Mock
+    lateinit var mediaClient: MediaClient
+
+    lateinit var testScheduler: TestScheduler
 
     val mediaList: ArrayList<Media> = ArrayList()
 
@@ -50,24 +51,26 @@ class DepictedImagesPresenterTest {
         mediaList.add(mediaItem)
         testObservable = Observable.just(mediaList)
         depictedImagesPresenter = DepictedImagesPresenter(jsonKvStore, depictsClient, mediaClient, testScheduler, testScheduler)
-        depictedImagesPresenter?.onAttachView(view)
+        depictedImagesPresenter.onAttachView(view)
     }
 
     @Test
     fun initList() {
-        Mockito.`when`(depictsClient?.fetchImagesForDepictedItem(ArgumentMatchers.anyString(),
+        Mockito.`when`(
-            ArgumentMatchers.anyInt())).thenReturn(testObservable)
+            depictsClient.fetchImagesForDepictedItem(ArgumentMatchers.anyString(),
-        depictedImagesPresenter?.initList("rabbit")
+                ArgumentMatchers.anyInt())
-        depictedImagesPresenter?.handleSuccess(mediaList)
+        ).thenReturn(testObservable)
+        depictedImagesPresenter.initList("rabbit")
+        depictedImagesPresenter.handleSuccess(mediaList)
         verify(view)?.handleSuccess(mediaList)
     }
 
     @Test
     fun replaceTitlesWithCaptions() {
         var stringObservable: Single<String>? = Single.just(String())
-        Mockito.`when`(mediaClient?.getCaptionByWikibaseIdentifier(ArgumentMatchers.anyString()))?.thenReturn(stringObservable)
+        Mockito.`when`(mediaClient.getCaptionByWikibaseIdentifier(ArgumentMatchers.anyString()))?.thenReturn(stringObservable)
-        depictedImagesPresenter?.replaceTitlesWithCaptions("File:rabbit.jpg", 0)
+        depictedImagesPresenter.replaceTitlesWithCaptions("File:rabbit.jpg", 0)
-        testScheduler?.triggerActions()
+        testScheduler.triggerActions()
         verify(view)?.handleLabelforImage("", 0)
     }
 }

app/src/test/kotlin/fr/free/nrw/commons/depictions/SubDepictionListPresenterTest.kt

@@ -7,7 +7,6 @@ import fr.free.nrw.commons.explore.recentsearches.RecentSearchesDao
 import fr.free.nrw.commons.mwapi.OkHttpJsonApiClient
 import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
 import io.reactivex.Observable
-import io.reactivex.Single
 import io.reactivex.schedulers.TestScheduler
 import org.junit.Before
 import org.junit.Test
@@ -20,19 +19,20 @@ import org.mockito.MockitoAnnotations
 class SubDepictionListPresenterTest {
 
     @Mock
-    internal var view: SubDepictionListContract.View? = null
+    internal lateinit var view: SubDepictionListContract.View
 
-    var subDepictionListPresenter: SubDepictionListPresenter? = null
+    lateinit var subDepictionListPresenter: SubDepictionListPresenter
 
-    var testScheduler: TestScheduler? = null
+    lateinit var testScheduler: TestScheduler
-
-    internal var recentSearchesDao: RecentSearchesDao? = null
 
     @Mock
-    internal var depictsClient: DepictsClient? = null
+    internal lateinit var recentSearchesDao: RecentSearchesDao
 
     @Mock
-    internal var okHttpJsonApiClient: OkHttpJsonApiClient? = null
+    internal lateinit var depictsClient: DepictsClient
+
+    @Mock
+    internal lateinit var okHttpJsonApiClient: OkHttpJsonApiClient
 
     var testObservable: Observable<List<DepictedItem>>? = null
 
@@ -49,22 +49,22 @@ class SubDepictionListPresenterTest {
         depictedItems.add(depictedItem)
         testObservable = Observable.just(depictedItems)
         subDepictionListPresenter = SubDepictionListPresenter(recentSearchesDao, depictsClient, okHttpJsonApiClient, testScheduler, testScheduler)
-        subDepictionListPresenter?.onAttachView(view)
+        subDepictionListPresenter.onAttachView(view)
     }
 
     @Test
     fun initSubDepictionListForParentClass() {
-        Mockito.`when`(okHttpJsonApiClient?.getParentQIDs(ArgumentMatchers.anyString())).thenReturn(testObservable)
+        Mockito.`when`(okHttpJsonApiClient.getParentQIDs(ArgumentMatchers.anyString())).thenReturn(testObservable)
-        subDepictionListPresenter?.initSubDepictionList("Q9394", true)
+        subDepictionListPresenter.initSubDepictionList("Q9394", true)
-        testScheduler?.triggerActions()
+        testScheduler.triggerActions()
         verify(view)?.onSuccess(depictedItems)
     }
 
     @Test
     fun initSubDepictionListForChildClass() {
-        Mockito.`when`(okHttpJsonApiClient?.getChildQIDs(ArgumentMatchers.anyString())).thenReturn(testObservable)
+        Mockito.`when`(okHttpJsonApiClient.getChildQIDs(ArgumentMatchers.anyString())).thenReturn(testObservable)
-        subDepictionListPresenter?.initSubDepictionList("Q9394", false)
+        subDepictionListPresenter.initSubDepictionList("Q9394", false)
-        testScheduler?.triggerActions()
+        testScheduler.triggerActions()
         verify(view)?.onSuccess(depictedItems)
     }
 }

app/src/test/kotlin/fr/free/nrw/commons/explore/depictions/SearchDepictionsDataSourceFactoryTest.kt

@@ -0,0 +1,53 @@
+package fr.free.nrw.commons.explore.depictions
+
+import com.nhaarman.mockitokotlin2.mock
+import com.nhaarman.mockitokotlin2.spy
+import com.nhaarman.mockitokotlin2.verify
+import io.reactivex.processors.PublishProcessor
+import org.hamcrest.MatcherAssert.assertThat
+import org.hamcrest.Matchers.`is`
+import org.junit.Before
+import org.junit.Ignore
+import org.junit.Test
+import org.mockito.Mock
+import org.mockito.Mockito
+import org.mockito.MockitoAnnotations
+
+class SearchDepictionsDataSourceFactoryTest {
+
+    @Mock
+    private lateinit var depictsClient: DepictsClient
+
+    @Mock
+    private lateinit var loadingStates: PublishProcessor<LoadingState>
+    private lateinit var factory: SearchDepictionsDataSourceFactory
+
+    @Before
+    fun setUp() {
+        MockitoAnnotations.initMocks(this)
+        factory = SearchDepictionsDataSourceFactory(depictsClient, "test", loadingStates)
+    }
+
+    @Test
+    fun `create returns a dataSource`() {
+        assertThat(
+            factory.create(),
+            `is`(SearchDepictionsDataSource(depictsClient, loadingStates, "test"))
+        )
+    }
+
+    @Test
+    @Ignore("Rewrite with Mockk constructor mocks")
+    fun `retryFailedRequest invokes method if not null`() {
+        val spyFactory = spy(factory)
+        val dataSource = mock<SearchDepictionsDataSource>()
+        Mockito.doReturn(dataSource).`when`(spyFactory).create()
+        factory.retryFailedRequest()
+        verify(dataSource).retryFailedRequest()
+    }
+
+    @Test
+    fun `retryFailedRequest does not invoke method if null`() {
+        factory.retryFailedRequest()
+    }
+}

app/src/test/kotlin/fr/free/nrw/commons/explore/depictions/SearchDepictionsDataSourceTest.kt

@@ -0,0 +1,106 @@
+package fr.free.nrw.commons.explore.depictions
+
+import androidx.paging.PositionalDataSource
+import com.nhaarman.mockitokotlin2.*
+import fr.free.nrw.commons.explore.depictions.LoadingState.*
+import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+import io.reactivex.Single
+import io.reactivex.plugins.RxJavaPlugins
+import io.reactivex.processors.PublishProcessor
+import io.reactivex.schedulers.Schedulers
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.mockito.Mock
+import org.mockito.MockitoAnnotations
+
+class SearchDepictionsDataSourceTest {
+
+    @Mock
+    private lateinit var depictsClient: DepictsClient
+
+    private lateinit var loadingStates: PublishProcessor<LoadingState>
+    private lateinit var searchDepictionsDataSource: SearchDepictionsDataSource
+
+    @Before
+    fun setUp() {
+        RxJavaPlugins.setIoSchedulerHandler { Schedulers.trampoline() }
+        MockitoAnnotations.initMocks(this)
+        loadingStates = PublishProcessor.create()
+        searchDepictionsDataSource =
+            SearchDepictionsDataSource(depictsClient, loadingStates, "test")
+    }
+
+    @After
+    fun tearDown() {
+        RxJavaPlugins.reset()
+    }
+
+    @Test
+    fun `loadInitial returns results and emits InitialLoad & Complete`() {
+        val params = PositionalDataSource.LoadInitialParams(0, 1, 2, false)
+        val callback = mock<PositionalDataSource.LoadInitialCallback<DepictedItem>>()
+        whenever(depictsClient.searchForDepictions("test", 1, 0))
+            .thenReturn(Single.just(emptyList()))
+        val testSubscriber = loadingStates.test()
+        searchDepictionsDataSource.loadInitial(params, callback)
+        verify(callback).onResult(emptyList(), 0)
+        testSubscriber.assertValues(InitialLoad, Complete)
+    }
+
+    @Test
+    fun `loadInitial onError does not return results and emits InitialLoad & Error`() {
+        val params = PositionalDataSource.LoadInitialParams(0, 1, 2, false)
+        val callback = mock<PositionalDataSource.LoadInitialCallback<DepictedItem>>()
+        whenever(depictsClient.searchForDepictions("test", 1, 0))
+            .thenThrow(RuntimeException())
+        val testSubscriber = loadingStates.test()
+        searchDepictionsDataSource.loadInitial(params, callback)
+        verify(callback, never()).onResult(any(), any())
+        testSubscriber.assertValues(InitialLoad, Error)
+    }
+
+    @Test
+    fun `loadRange returns results and emits Loading & Complete`() {
+        val callback: PositionalDataSource.LoadRangeCallback<DepictedItem> = mock()
+        val params = PositionalDataSource.LoadRangeParams(0, 1)
+        whenever(depictsClient.searchForDepictions("test", params.loadSize, params.startPosition))
+            .thenReturn(Single.just(emptyList()))
+        val testSubscriber = loadingStates.test()
+        searchDepictionsDataSource.loadRange(params, callback)
+        verify(callback).onResult(emptyList())
+        testSubscriber.assertValues(Loading, Complete)
+    }
+
+    @Test
+    fun `loadRange onError does not return results and emits Loading & Error`() {
+        val callback: PositionalDataSource.LoadRangeCallback<DepictedItem> = mock()
+        val params = PositionalDataSource.LoadRangeParams(0, 1)
+        whenever(depictsClient.searchForDepictions("test", params.loadSize, params.startPosition))
+            .thenThrow(RuntimeException())
+        val testSubscriber = loadingStates.test()
+        searchDepictionsDataSource.loadRange(params, callback)
+        verify(callback, never()).onResult(any())
+        testSubscriber.assertValues(Loading, Error)
+    }
+
+    @Test
+    fun `retryFailedRequest does nothing when null`() {
+        searchDepictionsDataSource.retryFailedRequest()
+        verifyNoMoreInteractions(depictsClient)
+    }
+
+    @Test
+    fun `retryFailedRequest retries last request`() {
+        val callback: PositionalDataSource.LoadRangeCallback<DepictedItem> = mock()
+        val params = PositionalDataSource.LoadRangeParams(0, 1)
+        whenever(depictsClient.searchForDepictions("test", params.loadSize, params.startPosition))
+            .thenThrow(RuntimeException()).thenReturn(Single.just(emptyList()))
+        val testSubscriber = loadingStates.test()
+        searchDepictionsDataSource.loadRange(params, callback)
+        verify(callback, never()).onResult(any())
+        searchDepictionsDataSource.retryFailedRequest()
+        verify(callback).onResult(emptyList())
+        testSubscriber.assertValues(Loading, Error, Loading, Complete)
+    }
+}

app/src/test/kotlin/fr/free/nrw/commons/explore/depictions/SearchDepictionsFragmentPresenterTest.kt

@@ -0,0 +1,136 @@
+package fr.free.nrw.commons.explore.depictions
+
+import androidx.arch.core.executor.testing.InstantTaskExecutorRule
+import androidx.lifecycle.LiveData
+import androidx.paging.PagedList
+import com.jraska.livedata.test
+import com.nhaarman.mockitokotlin2.*
+import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+import io.reactivex.processors.PublishProcessor
+import io.reactivex.schedulers.TestScheduler
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.mockito.Mock
+import org.mockito.MockitoAnnotations
+
+class SearchDepictionsFragmentPresenterTest {
+
+    @Rule
+    @JvmField
+    var instantTaskExecutorRule = InstantTaskExecutorRule()
+
+    @Mock
+    internal lateinit var view: SearchDepictionsFragmentContract.View
+
+    private lateinit var searchDepictionsFragmentPresenter: SearchDepictionsFragmentPresenter
+
+    private lateinit var testScheduler: TestScheduler
+
+    @Mock
+    private lateinit var searchableDepictionsDataSourceFactory: SearchableDepictionsDataSourceFactory
+
+    private var loadingStates: PublishProcessor<LoadingState> = PublishProcessor.create()
+
+    private var searchResults: PublishProcessor<LiveData<PagedList<DepictedItem>>> =
+        PublishProcessor.create()
+
+    private var noItemLoadedEvent: PublishProcessor<Unit> = PublishProcessor.create()
+
+    @Before
+    @Throws(Exception::class)
+    fun setUp() {
+        MockitoAnnotations.initMocks(this)
+        whenever(searchableDepictionsDataSourceFactory.searchResults).thenReturn(searchResults)
+        whenever(searchableDepictionsDataSourceFactory.loadingStates).thenReturn(loadingStates)
+        whenever(searchableDepictionsDataSourceFactory.noItemsLoadedEvent)
+            .thenReturn(noItemLoadedEvent)
+        testScheduler = TestScheduler()
+        searchDepictionsFragmentPresenter = SearchDepictionsFragmentPresenter(
+            testScheduler,
+            searchableDepictionsDataSourceFactory
+        )
+        searchDepictionsFragmentPresenter.onAttachView(view)
+    }
+
+    @Test
+    fun `searchResults emission updates the view`() {
+        val pagedListLiveData = mock<LiveData<PagedList<DepictedItem>>>()
+        searchResults.offer(pagedListLiveData)
+        verify(view).observeSearchResults(pagedListLiveData)
+    }
+
+    @Test
+    fun `Loading offers a loading list item`() {
+        onLoadingState(LoadingState.Loading)
+        searchDepictionsFragmentPresenter.listFooterData.test()
+            .assertValue(listOf(FooterItem.LoadingItem))
+    }
+
+    @Test
+    fun `Complete offers an empty list item and hides initial loader`() {
+        onLoadingState(LoadingState.Complete)
+        searchDepictionsFragmentPresenter.listFooterData.test()
+            .assertValue(emptyList())
+        verify(view).hideInitialLoadProgress()
+    }
+
+    @Test
+    fun `InitialLoad shows initial loader`() {
+        onLoadingState(LoadingState.InitialLoad)
+        verify(view).showInitialLoadInProgress()
+    }
+
+    @Test
+    fun `Error offers a refresh list item, hides initial loader and shows error with a set text`() {
+        searchDepictionsFragmentPresenter.onQueryUpdated("test")
+        onLoadingState(LoadingState.Error)
+        verify(view).setEmptyViewText("test")
+        verify(view).showSnackbar()
+        verify(view).hideInitialLoadProgress()
+        searchDepictionsFragmentPresenter.listFooterData.test()
+            .assertValue(listOf(FooterItem.RefreshItem))
+    }
+
+    @Test
+    fun `Error offers a refresh list item, hides initial loader and shows error with a unset text`() {
+        onLoadingState(LoadingState.Error)
+        verify(view, never()).setEmptyViewText(any())
+        verify(view).showSnackbar()
+        verify(view).hideInitialLoadProgress()
+        searchDepictionsFragmentPresenter.listFooterData.test()
+            .assertValue(listOf(FooterItem.RefreshItem))
+    }
+
+    @Test
+    fun `no Items event sets empty view text`() {
+        searchDepictionsFragmentPresenter.onQueryUpdated("test")
+        noItemLoadedEvent.offer(Unit)
+        verify(view).setEmptyViewText("test")
+    }
+
+    @Test
+    fun `retryFailedRequest calls retry`() {
+        searchDepictionsFragmentPresenter.retryFailedRequest()
+        verify(searchableDepictionsDataSourceFactory).retryFailedRequest()
+    }
+
+    @Test
+    fun `onDetachView stops subscriptions`() {
+        searchDepictionsFragmentPresenter.onDetachView()
+        onLoadingState(LoadingState.Loading)
+        searchDepictionsFragmentPresenter.listFooterData.test()
+            .assertValue(emptyList())
+    }
+
+    @Test
+    fun `onQueryUpdated updates dataSourceFactory`() {
+        searchDepictionsFragmentPresenter.onQueryUpdated("test")
+        verify(searchableDepictionsDataSourceFactory).onQueryUpdated("test")
+    }
+
+    private fun onLoadingState(loadingState: LoadingState) {
+        loadingStates.offer(loadingState)
+        testScheduler.triggerActions()
+    }
+}

app/src/test/kotlin/fr/free/nrw/commons/explore/depictions/SearchDepictionsPresenterTest.kt

@@ -1,57 +0,0 @@
-package fr.free.nrw.commons.explore.depictions
-
-import com.nhaarman.mockitokotlin2.whenever
-import depictedItem
-import fr.free.nrw.commons.explore.recentsearches.RecentSearchesDao
-import fr.free.nrw.commons.kvstore.JsonKvStore
-import io.reactivex.Single
-import io.reactivex.schedulers.TestScheduler
-import org.junit.Before
-import org.junit.Test
-import org.mockito.Mock
-import org.mockito.Mockito.verify
-import org.mockito.MockitoAnnotations
-
-class SearchDepictionsPresenterTest {
-
-    @Mock
-    internal lateinit var view: SearchDepictionsFragmentContract.View
-
-    private lateinit var searchDepictionsFragmentPresenter: SearchDepictionsFragmentPresenter
-
-    private lateinit var testScheduler: TestScheduler
-
-    @Mock
-    private lateinit var jsonKvStore: JsonKvStore
-
-    @Mock
-    lateinit var recentSearchesDao: RecentSearchesDao
-
-    @Mock
-    lateinit var depictsClient: DepictsClient
-
-    @Before
-    @Throws(Exception::class)
-    fun setUp() {
-        MockitoAnnotations.initMocks(this)
-        testScheduler = TestScheduler()
-        searchDepictionsFragmentPresenter = SearchDepictionsFragmentPresenter(
-            jsonKvStore,
-            recentSearchesDao,
-            depictsClient,
-            testScheduler,
-            testScheduler
-        )
-        searchDepictionsFragmentPresenter.onAttachView(view)
-    }
-
-    @Test
-    fun updateDepictionList() {
-        val expectedList = listOf(depictedItem())
-        whenever(depictsClient.searchForDepictions("rabbit", 25, 0))
-            .thenReturn(Single.just(expectedList))
-        searchDepictionsFragmentPresenter.updateDepictionList("rabbit", 25, false)
-        testScheduler.triggerActions()
-        verify(view)?.onSuccess(expectedList)
-    }
-}

app/src/test/kotlin/fr/free/nrw/commons/explore/depictions/SearchableDepictionsDataSourceFactoryTest.kt

@@ -0,0 +1,80 @@
+package fr.free.nrw.commons.explore.depictions
+
+import androidx.lifecycle.LiveData
+import androidx.paging.PagedList
+import com.nhaarman.mockitokotlin2.*
+import fr.free.nrw.commons.upload.structure.depictions.DepictedItem
+import io.reactivex.processors.PublishProcessor
+import org.junit.Before
+import org.junit.Test
+import org.mockito.Mock
+import org.mockito.MockitoAnnotations
+
+class SearchableDepictionsDataSourceFactoryTest {
+
+    @Mock
+    private lateinit var searchDepictionsDataSourceFactoryFactory: SearchDepictionsDataSourceFactoryFactory
+
+    @Mock
+    private lateinit var liveDataConverter: LiveDataConverter
+
+    private lateinit var factory: SearchableDepictionsDataSourceFactory
+
+
+    @Before
+    fun setUp() {
+        MockitoAnnotations.initMocks(this)
+        factory = SearchableDepictionsDataSourceFactory(
+            searchDepictionsDataSourceFactoryFactory,
+            liveDataConverter
+        )
+    }
+
+    @Test
+    fun `onQueryUpdated emits new liveData`() {
+        val (_, liveData) = expectNewLiveData()
+        factory.searchResults.test()
+            .also { factory.onQueryUpdated("test") }
+            .assertValue(liveData)
+    }
+
+    @Test
+    fun `onQueryUpdated invokes livedatconverter with no items emitter`() {
+        val (captor, _) = expectNewLiveData()
+        factory.onQueryUpdated("test")
+        factory.noItemsLoadedEvent.test()
+            .also { captor.firstValue.invoke() }
+            .assertValue(Unit)
+    }
+
+    /*
+    * Just for coverage, no way to really assert this
+    * */
+    @Test
+    fun `retryFailedRequest does nothing without a factory`() {
+        factory.retryFailedRequest()
+    }
+
+    @Test
+    fun `retryFailedRequest retries with a factory`() {
+        val (_, _, dataSourceFactory) = expectNewLiveData()
+        factory.onQueryUpdated("test")
+        factory.retryFailedRequest()
+        verify(dataSourceFactory).retryFailedRequest()
+    }
+
+    private fun expectNewLiveData(): Triple<KArgumentCaptor<() -> Unit>, LiveData<PagedList<DepictedItem>>, SearchDepictionsDataSourceFactory> {
+        val dataSourceFactory: SearchDepictionsDataSourceFactory = mock()
+        whenever(
+            searchDepictionsDataSourceFactoryFactory.create(
+                "test",
+                factory.loadingStates as PublishProcessor<LoadingState>
+            )
+        ).thenReturn(dataSourceFactory)
+        val captor = argumentCaptor<() -> Unit>()
+        val liveData: LiveData<PagedList<DepictedItem>> = mock()
+        whenever(liveDataConverter.convert(eq(dataSourceFactory), captor.capture()))
+            .thenReturn(liveData)
+        return Triple(captor, liveData, dataSourceFactory)
+    }
+}

app/src/test/kotlin/fr/free/nrw/commons/upload/UploadPresenterTest.kt

@@ -12,7 +12,7 @@ import org.mockito.InjectMocks
 import org.mockito.Mock
 import org.mockito.Mockito.`when`
 import org.mockito.MockitoAnnotations
-import java.util.ArrayList
+import java.util.*
 
 
 /**
@@ -21,11 +21,11 @@ import java.util.ArrayList
 class UploadPresenterTest {
 
     @Mock
-    internal var repository: UploadRepository? = null
+    internal lateinit var repository: UploadRepository
     @Mock
-    internal var view: UploadContract.View? = null
+    internal lateinit var view: UploadContract.View
     @Mock
-    var contribution: Contribution? = null
+    lateinit var contribution: Contribution
 
     @Mock
     private lateinit var uploadableFile: UploadableFile
@@ -34,7 +34,7 @@ class UploadPresenterTest {
     private lateinit var anotherUploadableFile: UploadableFile
 
     @InjectMocks
-    var uploadPresenter: UploadPresenter? = null
+    lateinit var uploadPresenter: UploadPresenter
 
     private var uploadableFiles: ArrayList<UploadableFile> = ArrayList()
 
@@ -45,11 +45,11 @@ class UploadPresenterTest {
     @Throws(Exception::class)
     fun setUp() {
         MockitoAnnotations.initMocks(this)
-        uploadPresenter?.onAttachView(view)
+        uploadPresenter.onAttachView(view)
-        `when`(repository?.buildContributions()).thenReturn(Observable.just(contribution))
+        `when`(repository.buildContributions()).thenReturn(Observable.just(contribution))
         uploadableFiles.add(uploadableFile)
-        `when`(view?.uploadableFiles).thenReturn(uploadableFiles)
+        `when`(view.uploadableFiles).thenReturn(uploadableFiles)
-        `when`(uploadableFile?.filePath).thenReturn("data://test")
+        `when`(uploadableFile.filePath).thenReturn("data://test")
     }
 
     /**
@@ -57,12 +57,12 @@ class UploadPresenterTest {
      */
     @Test
     fun handleSubmitTestUserLoggedIn() {
-        `when`(view?.isLoggedIn).thenReturn(true)
+        `when`(view.isLoggedIn).thenReturn(true)
-        uploadPresenter?.handleSubmit()
+        uploadPresenter.handleSubmit()
-        verify(view)?.isLoggedIn
+        verify(view).isLoggedIn
-        verify(view)?.showProgress(true)
+        verify(view).showProgress(true)
-        verify(repository)?.buildContributions()
+        verify(repository).buildContributions()
-        verify(repository)?.buildContributions()
+        verify(repository).buildContributions()
     }
 
     /**
@@ -70,10 +70,10 @@ class UploadPresenterTest {
      */
     @Test
     fun handleSubmitTestUserNotLoggedIn() {
-        `when`(view?.isLoggedIn).thenReturn(false)
+        `when`(view.isLoggedIn).thenReturn(false)
-        uploadPresenter?.handleSubmit()
+        uploadPresenter.handleSubmit()
-        verify(view)?.isLoggedIn
+        verify(view).isLoggedIn
-        verify(view)?.askUserToLogIn()
+        verify(view).askUserToLogIn()
 
     }
 
@@ -88,9 +88,9 @@ class UploadPresenterTest {
     fun hideTopCardWhenReachedTheLastFile(){
         deletePictureBaseTest()
         uploadableFiles.add(uploadableFile)
-        uploadPresenter?.deletePictureAtIndex(0)
+        uploadPresenter.deletePictureAtIndex(0)
-        verify(view)?.showHideTopCard(false)
+        verify(view).showHideTopCard(false)
-        verify(repository)?.deletePicture(ArgumentMatchers.anyString())
+        verify(repository).deletePicture(ArgumentMatchers.anyString())
     }
 
     /**
@@ -100,11 +100,11 @@ class UploadPresenterTest {
     fun testDeleteWhenSingleUpload(){
         deletePictureBaseTest()
         uploadableFiles.add(uploadableFile)
-        uploadPresenter?.deletePictureAtIndex(0)
+        uploadPresenter.deletePictureAtIndex(0)
-        verify(view)?.showHideTopCard(false)
+        verify(view).showHideTopCard(false)
-        verify(repository)?.deletePicture(ArgumentMatchers.anyString())
+        verify(repository).deletePicture(ArgumentMatchers.anyString())
-        verify(view)?.showMessage(ArgumentMatchers.anyInt())//As there is only one while which we are asking for deletion, upload should be cancelled and this flow should be triggered
+        verify(view).showMessage(ArgumentMatchers.anyInt())//As there is only one while which we are asking for deletion, upload should be cancelled and this flow should be triggered
-        verify(view)?.finish()
+        verify(view).finish()
     }
 
     /**
@@ -115,8 +115,8 @@ class UploadPresenterTest {
         deletePictureBaseTest()
         uploadableFiles.add(uploadableFile)
         uploadableFiles.add(anotherUploadableFile)
-        uploadPresenter?.deletePictureAtIndex(0)
+        uploadPresenter.deletePictureAtIndex(0)
-        verify(view)?.onUploadMediaDeleted(0)
+        verify(view).onUploadMediaDeleted(0)
-        verify(view)?.updateTopCardTitle()
+        verify(view).updateTopCardTitle()
     }
 }

gradle.properties

@@ -24,6 +24,7 @@ ROOM_VERSION=2.2.3
 PREFERENCE_VERSION=1.1.0
 CORE_KTX_VERSION=1.2.0
 ADAPTER_DELEGATES_VERSION=4.3.0
+PAGING_VERSION=2.1.2
 MULTIDEX_VERSION=2.0.1
 
 systemProp.http.proxyPort=0