#3822 Convert SubCategoryImagesListFragment to use Pagination - convert subcategories - add continuation support in category client - rely on interfaces for callbacks of PageableMediaFragments

app/src/main/java/fr/free/nrw/commons/bookmarks/BookmarksActivity.java

@@ -142,4 +142,9 @@ public class BookmarksActivity extends NavigationBaseActivity
 
     @Override
     public void requestMoreImages() { }
+
+    @Override
+    public void onMediaClicked(int position) {
+        //TODO use with pagination
+    }
 }

app/src/main/java/fr/free/nrw/commons/category/CategoriesModel.kt

@@ -93,6 +93,7 @@ class CategoriesModel @Inject constructor(
         else
             categoryClient.searchCategoriesForPrefix(term.toLowerCase(), SEARCH_CATS_LIMIT)
                 .map { it.sortedWith(StringSortingUtils.sortBySimilarity(term)) }
+                .toObservable()
     }
 
     private fun categoriesFromDepiction(selectedDepictions: List<DepictedItem>) =
@@ -126,7 +127,7 @@ class CategoriesModel @Inject constructor(
      * @return
      */
     private fun getTitleCategories(title: String): Observable<List<String>> {
-        return categoryClient.searchCategories(title.toLowerCase(), SEARCH_CATS_LIMIT)
+        return categoryClient.searchCategories(title.toLowerCase(), SEARCH_CATS_LIMIT).toObservable()
     }
 
 

app/src/main/java/fr/free/nrw/commons/category/CategoryClient.kt

@@ -1,16 +1,22 @@
 package fr.free.nrw.commons.category
 
-import io.reactivex.Observable
+import io.reactivex.Single
 import org.wikipedia.dataclient.mwapi.MwQueryResponse
 import javax.inject.Inject
 import javax.inject.Singleton
 
 const val CATEGORY_PREFIX = "Category:"
+const val SUB_CATEGORY_CONTINUATION_PREFIX = "sub_category_"
+
 /**
  * Category Client to handle custom calls to Commons MediaWiki APIs
  */
 @Singleton
 class CategoryClient @Inject constructor(private val categoryInterface: CategoryInterface) {
+
+    private val continuationStore: MutableMap<String, Map<String, String>?> = mutableMapOf()
+    private val continuationExists: MutableMap<String, Boolean> = mutableMapOf()
+
     /**
      * Searches for categories containing the specified string.
      *
@@ -21,8 +27,10 @@ class CategoryClient @Inject constructor(private val categoryInterface: Category
      */
     @JvmOverloads
     fun searchCategories(filter: String?, itemLimit: Int, offset: Int = 0):
-            Observable<List<String>> {
+            Single<List<String>> {
-        return responseToCategoryName(categoryInterface.searchCategories(filter, itemLimit, offset))
+        return responseToCategoryName(
+            categoryInterface.searchCategories(filter, itemLimit, offset)
+        )
     }
 
     /**
@@ -35,7 +43,7 @@ class CategoryClient @Inject constructor(private val categoryInterface: Category
      */
     @JvmOverloads
     fun searchCategoriesForPrefix(prefix: String?, itemLimit: Int, offset: Int = 0):
-            Observable<List<String>> {
+            Single<List<String>> {
         return responseToCategoryName(
             categoryInterface.searchCategoriesForPrefix(prefix, itemLimit, offset)
         )
@@ -48,8 +56,19 @@ class CategoryClient @Inject constructor(private val categoryInterface: Category
      * @param categoryName Category name as defined on commons
      * @return Observable emitting the categories returned. If our search yielded "Category:Test", "Test" is emitted.
      */
-    fun getSubCategoryList(categoryName: String?): Observable<List<String>> {
+    fun getSubCategoryList(categoryName: String?): Single<List<String>> {
-        return responseToCategoryName(categoryInterface.getSubCategoryList(categoryName))
+        val key = "$SUB_CATEGORY_CONTINUATION_PREFIX$categoryName"
+        return if (hasMorePagesFor(key)) {
+            responseToCategoryName(
+                categoryInterface.getSubCategoryList(
+                    categoryName,
+                    continuationStore[key] ?: emptyMap()
+                ),
+                key
+            )
+        } else {
+            Single.just(emptyList())
+        }
     }
 
     /**
@@ -59,7 +78,7 @@ class CategoryClient @Inject constructor(private val categoryInterface: Category
      * @param categoryName Category name as defined on commons
      * @return
      */
-    fun getParentCategoryList(categoryName: String?): Observable<List<String>> {
+    fun getParentCategoryList(categoryName: String?): Single<List<String>> {
         return responseToCategoryName(categoryInterface.getParentCategoryList(categoryName))
     }
 
@@ -69,12 +88,30 @@ class CategoryClient @Inject constructor(private val categoryInterface: Category
      * @param responseObservable The query response observable
      * @return Observable emitting the categories returned. If our search yielded "Category:Test", "Test" is emitted.
      */
-    private fun responseToCategoryName(responseObservable: Observable<MwQueryResponse>): Observable<List<String>> {
+    private fun responseToCategoryName(
+        responseObservable: Single<MwQueryResponse>,
+        key: String? = null
+    ): Single<List<String>> {
         return responseObservable
-            .map { it.query()?.pages() ?: emptyList() }
+            .map {
+                if (key != null) {
+                    continuationExists[key] =
+                        it.continuation()?.let { continuation ->
+                            continuationStore[key] = continuation
+                            true
+                        } ?: false
+                }
+                it.query()?.pages() ?: emptyList()
+            }
             .map {
                 it.map { page -> page.title().replace(CATEGORY_PREFIX, "") }
             }
     }
 
+    private fun hasMorePagesFor(key: String) = continuationExists[key] ?: true
+
+    fun resetSubCategoryContinuation(category: String) {
+        continuationExists.remove("$SUB_CATEGORY_CONTINUATION_PREFIX$category")
+        continuationStore.remove("$SUB_CATEGORY_CONTINUATION_PREFIX$category")
+    }
 }

app/src/main/java/fr/free/nrw/commons/category/CategoryDetailsActivity.java

@@ -20,6 +20,7 @@ import fr.free.nrw.commons.R;
 import fr.free.nrw.commons.Utils;
 import fr.free.nrw.commons.explore.ViewPagerAdapter;
 import fr.free.nrw.commons.explore.categories.media.CategoriesMediaFragment;
+import fr.free.nrw.commons.explore.categories.sub.SubCategoriesFragment;
 import fr.free.nrw.commons.media.MediaDetailPagerFragment;
 import fr.free.nrw.commons.theme.NavigationBaseActivity;
 import java.util.ArrayList;
@@ -69,13 +70,12 @@ public class CategoryDetailsActivity extends NavigationBaseActivity
         List<Fragment> fragmentList = new ArrayList<>();
         List<String> titleList = new ArrayList<>();
         categoriesMediaFragment = new CategoriesMediaFragment();
-        SubCategoryListFragment subCategoryListFragment = new SubCategoryListFragment();
+        SubCategoriesFragment subCategoryListFragment = new SubCategoriesFragment();
         SubCategoryListFragment parentCategoryListFragment = new SubCategoryListFragment();
         categoryName = getIntent().getStringExtra("categoryName");
         if (getIntent() != null && categoryName != null) {
             Bundle arguments = new Bundle();
             arguments.putString("categoryName", categoryName);
-            arguments.putBoolean("isParentCategory", false);
             categoriesMediaFragment.setArguments(arguments);
             subCategoryListFragment.setArguments(arguments);
             Bundle parentCategoryArguments = new Bundle();

app/src/main/java/fr/free/nrw/commons/category/CategoryImagesActivity.java

@@ -195,4 +195,9 @@ public class CategoryImagesActivity
     public void requestMoreImages() {
         //unneeded
     }
+
+    @Override
+    public void onMediaClicked(int position) {
+        // this class is unused and will be deleted
+    }
 }

app/src/main/java/fr/free/nrw/commons/category/CategoryImagesCallback.java

@@ -8,6 +8,7 @@ package fr.free.nrw.commons.category;
 public interface CategoryImagesCallback {
    void viewPagerNotifyDataSetChanged();
    void requestMoreImages();
+   void onMediaClicked(int position);
 }
 
 

app/src/main/java/fr/free/nrw/commons/category/CategoryInterface.java

@@ -1,10 +1,11 @@
 package fr.free.nrw.commons.category;
 
+import io.reactivex.Single;
+import java.util.Map;
 import org.wikipedia.dataclient.mwapi.MwQueryResponse;
-
-import io.reactivex.Observable;
 import retrofit2.http.GET;
 import retrofit2.http.Query;
+import retrofit2.http.QueryMap;
 
 /**
  * Interface for interacting with Commons category related APIs
@@ -20,7 +21,7 @@ public interface CategoryInterface {
      */
     @GET("w/api.php?action=query&format=json&formatversion=2"
             + "&generator=search&gsrnamespace=14")
-    Observable<MwQueryResponse> searchCategories(@Query("gsrsearch") String filter,
+    Single<MwQueryResponse> searchCategories(@Query("gsrsearch") String filter,
                                                  @Query("gsrlimit") int itemLimit, @Query("gsroffset") int offset);
 
     /**
@@ -32,16 +33,17 @@ public interface CategoryInterface {
      */
     @GET("w/api.php?action=query&format=json&formatversion=2"
             + "&generator=allcategories")
-    Observable<MwQueryResponse> searchCategoriesForPrefix(@Query("gacprefix") String prefix,
+    Single<MwQueryResponse> searchCategoriesForPrefix(@Query("gacprefix") String prefix,
                                                           @Query("gaclimit") int itemLimit, @Query("gacoffset") int offset);
 
     @GET("w/api.php?action=query&format=json&formatversion=2"
             + "&generator=categorymembers&gcmtype=subcat"
-            + "&prop=info&gcmlimit=500")
+            + "&prop=info&gcmlimit=50")
-    Observable<MwQueryResponse> getSubCategoryList(@Query("gcmtitle") String categoryName);
+    Single<MwQueryResponse> getSubCategoryList(@Query("gcmtitle") String categoryName,
+        @QueryMap(encoded = true) Map<String, String> continuation);
 
     @GET("w/api.php?action=query&format=json&formatversion=2"
             + "&generator=categories&prop=info&gcllimit=500")
-    Observable<MwQueryResponse> getParentCategoryList(@Query("titles") String categoryName);
+    Single<MwQueryResponse> getParentCategoryList(@Query("titles") String categoryName);
 
 }

app/src/main/java/fr/free/nrw/commons/di/FragmentBuilderModule.java

@@ -8,6 +8,7 @@ import fr.free.nrw.commons.category.SubCategoryListFragment;
 import fr.free.nrw.commons.contributions.ContributionsFragment;
 import fr.free.nrw.commons.contributions.ContributionsListFragment;
 import fr.free.nrw.commons.explore.categories.media.CategoriesMediaFragment;
+import fr.free.nrw.commons.explore.categories.sub.SubCategoriesFragment;
 import fr.free.nrw.commons.explore.depictions.child.ChildDepictionsFragment;
 import fr.free.nrw.commons.explore.depictions.media.DepictedImagesFragment;
 import fr.free.nrw.commons.explore.depictions.parent.ParentDepictionsFragment;
@@ -99,4 +100,7 @@ public abstract class FragmentBuilderModule {
 
     @ContributesAndroidInjector
     abstract CategoriesMediaFragment bindCategoriesMediaFragment();
+
+    @ContributesAndroidInjector
+    abstract SubCategoriesFragment bindSubCategoriesFragment();
 }

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

@@ -7,7 +7,6 @@ import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
-import android.widget.AdapterView;
 import android.widget.FrameLayout;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
@@ -31,8 +30,7 @@ import java.util.List;
 
 public class ExploreActivity
         extends NavigationBaseActivity
-        implements MediaDetailPagerFragment.MediaDetailProvider,
+        implements MediaDetailPagerFragment.MediaDetailProvider, CategoryImagesCallback {
-        AdapterView.OnItemClickListener, CategoryImagesCallback {
 
     private static final String FEATURED_IMAGES_CATEGORY = "Featured_pictures_on_Wikimedia_Commons";
     private static final String MOBILE_UPLOADS_CATEGORY = "Uploaded_with_Mobile/Android";
@@ -177,7 +175,7 @@ public class ExploreActivity
      * This method is called onClick of media inside category featured images or mobile uploads.
      */
     @Override
-    public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
+    public void onMediaClicked( int position) {
         tabLayout.setVisibility(View.GONE);
         viewPager.setVisibility(View.GONE);
         mediaContainer.setVisibility(View.VISIBLE);
@@ -195,7 +193,7 @@ public class ExploreActivity
             // coming back to the explore activity. See https://github.com/commons-app/apps-android-commons/issues/1631
             // https://stackoverflow.com/questions/11353075/how-can-i-maintain-fragment-state-when-added-to-the-back-stack/19022550#19022550            supportFragmentManager.executePendingTransactions();
         }
-        mediaDetails.showImage(i);
+        mediaDetails.showImage(position);
         forceInitBackButton();
     }
 

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

@@ -191,7 +191,8 @@ public class SearchActivity extends NavigationBaseActivity
      * Open media detail pager fragment on click of image in search results
      * @param index item index that should be opened
      */
-    public void onSearchImageClicked(int index) {
+    @Override
+    public void onMediaClicked(int index) {
         ViewUtil.hideKeyboard(this.findViewById(R.id.searchBox));
         toolbar.setVisibility(View.GONE);
         tabLayout.setVisibility(View.GONE);

app/src/main/java/fr/free/nrw/commons/explore/categories/CategoriesModule.kt

@@ -4,12 +4,18 @@ import dagger.Binds
 import dagger.Module
 import fr.free.nrw.commons.explore.categories.media.CategoryMediaPresenter
 import fr.free.nrw.commons.explore.categories.media.CategoryMediaPresenterImpl
+import fr.free.nrw.commons.explore.categories.sub.SubCategoriesPresenter
+import fr.free.nrw.commons.explore.categories.sub.SubCategoriesPresenterImpl
 
 
 @Module
 abstract class CategoriesModule {
 
     @Binds
-    abstract fun CategoryMediaPresenterImpl.bindsParentDepictionPresenter()
+    abstract fun CategoryMediaPresenterImpl.bindsCategoryMediaPresenter()
             : CategoryMediaPresenter
+
+    @Binds
+    abstract fun SubCategoriesPresenterImpl.bindsSubCategoriesPresenter()
+            : SubCategoriesPresenter
 }

app/src/main/java/fr/free/nrw/commons/explore/categories/media/CategoriesMediaFragment.kt

@@ -3,8 +3,6 @@ package fr.free.nrw.commons.explore.categories.media
 import android.os.Bundle
 import android.view.View
 import fr.free.nrw.commons.category.CATEGORY_PREFIX
-import fr.free.nrw.commons.category.CategoryDetailsActivity
-import fr.free.nrw.commons.category.CategoryImagesCallback
 import fr.free.nrw.commons.explore.media.PageableMediaFragment
 import javax.inject.Inject
 
@@ -20,12 +18,4 @@ class CategoriesMediaFragment : PageableMediaFragment() {
         super.onViewCreated(view, savedInstanceState)
         onQueryUpdated("$CATEGORY_PREFIX${arguments!!.getString("categoryName")!!}")
     }
-
-    override fun onItemClicked(position: Int) {
-        (activity as CategoryDetailsActivity).onMediaClicked(position)
-    }
-
-    override fun notifyViewPager() {
-        (activity as CategoryImagesCallback).viewPagerNotifyDataSetChanged()
-    }
 }

app/src/main/java/fr/free/nrw/commons/explore/categories/search/PageableCategoriesDataSource.kt

@@ -11,6 +11,6 @@ class PageableCategoriesDataSource @Inject constructor(
 ) : PageableBaseDataSource<String>(liveDataConverter) {
 
     override val loadFunction = { loadSize: Int, startPosition: Int ->
-        categoryClient.searchCategories(query, loadSize, startPosition).blockingFirst()
+        categoryClient.searchCategories(query, loadSize, startPosition).blockingGet()
     }
 }

app/src/main/java/fr/free/nrw/commons/explore/categories/search/PageableCategoryFragment.kt

@@ -0,0 +1,15 @@
+package fr.free.nrw.commons.explore.categories.search
+
+import fr.free.nrw.commons.R
+import fr.free.nrw.commons.category.CategoryDetailsActivity
+import fr.free.nrw.commons.explore.paging.BasePagingFragment
+
+
+abstract class PageableCategoryFragment : BasePagingFragment<String>() {
+    override val errorTextId: Int = R.string.error_loading_categories
+    override val pagedListAdapter by lazy {
+        PagedSearchCategoriesAdapter {
+            CategoryDetailsActivity.startYourself(context, it)
+        }
+    }
+}

app/src/main/java/fr/free/nrw/commons/explore/categories/search/SearchCategoryFragment.kt

@@ -8,20 +8,12 @@ import javax.inject.Inject
 /**
  * Displays the category search screen.
  */
-class SearchCategoryFragment : BasePagingFragment<String>() {
+class SearchCategoryFragment : PageableCategoryFragment() {
     @Inject
     lateinit var presenter: SearchCategoriesFragmentPresenter
 
-    override val errorTextId: Int = R.string.error_loading_categories
-
     override val injectedPresenter
         get() = presenter
 
-    override val pagedListAdapter by lazy {
-        PagedSearchCategoriesAdapter {
-            CategoryDetailsActivity.startYourself(context, it)
-        }
-    }
-
     override fun getEmptyText(query: String) = getString(R.string.categories_not_found, query)
 }

app/src/main/java/fr/free/nrw/commons/explore/categories/sub/PageableSubCategoriesDataSource.kt

@@ -0,0 +1,19 @@
+package fr.free.nrw.commons.explore.categories.sub
+
+import fr.free.nrw.commons.category.CategoryClient
+import fr.free.nrw.commons.explore.paging.LiveDataConverter
+import fr.free.nrw.commons.explore.paging.PageableBaseDataSource
+import javax.inject.Inject
+
+class PageableSubCategoriesDataSource @Inject constructor(
+    liveDataConverter: LiveDataConverter,
+    val categoryClient: CategoryClient
+) : PageableBaseDataSource<String>(liveDataConverter) {
+
+    override val loadFunction = { loadSize: Int, startPosition: Int ->
+        if (startPosition == 0) {
+            categoryClient.resetSubCategoryContinuation(query)
+        }
+        categoryClient.getSubCategoryList(query).blockingGet()
+    }
+}

app/src/main/java/fr/free/nrw/commons/explore/categories/sub/SubCategoriesFragment.kt

@@ -0,0 +1,25 @@
+package fr.free.nrw.commons.explore.categories.sub
+
+import android.os.Bundle
+import android.view.View
+import fr.free.nrw.commons.R
+import fr.free.nrw.commons.category.CATEGORY_PREFIX
+import fr.free.nrw.commons.explore.categories.search.PageableCategoryFragment
+import fr.free.nrw.commons.explore.paging.PagingContract
+import javax.inject.Inject
+
+
+class SubCategoriesFragment : PageableCategoryFragment() {
+
+    @Inject lateinit var presenter: SubCategoriesPresenter
+
+    override val injectedPresenter: PagingContract.Presenter<String>
+        get() = presenter
+
+    override fun getEmptyText(query: String) = getString(R.string.no_subcategory_found)
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        onQueryUpdated("$CATEGORY_PREFIX${arguments!!.getString("categoryName")!!}")
+    }
+}

app/src/main/java/fr/free/nrw/commons/explore/categories/sub/SubCategoriesPresenterImpl.kt

@@ -0,0 +1,16 @@
+package fr.free.nrw.commons.explore.categories.sub
+
+import fr.free.nrw.commons.di.CommonsApplicationModule
+import fr.free.nrw.commons.explore.paging.BasePagingPresenter
+import fr.free.nrw.commons.explore.paging.PagingContract
+import io.reactivex.Scheduler
+import javax.inject.Inject
+import javax.inject.Named
+
+interface SubCategoriesPresenter : PagingContract.Presenter<String>
+
+class SubCategoriesPresenterImpl @Inject constructor(
+    @Named(CommonsApplicationModule.MAIN_THREAD) mainThreadScheduler: Scheduler,
+    dataSourceFactory: PageableSubCategoriesDataSource
+) : BasePagingPresenter<String>(mainThreadScheduler, dataSourceFactory),
+    SubCategoriesPresenter

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

@@ -2,7 +2,6 @@ package fr.free.nrw.commons.explore.depictions.media
 
 import android.os.Bundle
 import android.view.View
-import fr.free.nrw.commons.explore.depictions.WikidataItemDetailsActivity
 import fr.free.nrw.commons.explore.media.PageableMediaFragment
 import javax.inject.Inject
 
@@ -18,11 +17,4 @@ class DepictedImagesFragment : PageableMediaFragment() {
         onQueryUpdated(arguments!!.getString("entityId")!!)
     }
 
-    override fun onItemClicked(position: Int) {
-        (activity as WikidataItemDetailsActivity).onMediaClicked(position)
-    }
-
-    override fun notifyViewPager() {
-        (activity as WikidataItemDetailsActivity).viewPagerNotifyDataSetChanged()
-    }
 }

app/src/main/java/fr/free/nrw/commons/explore/media/PageableMediaFragment.kt

@@ -1,25 +1,38 @@
 package fr.free.nrw.commons.explore.media
 
+import android.content.Context
 import android.os.Bundle
 import android.view.View
 import fr.free.nrw.commons.Media
 import fr.free.nrw.commons.R
+import fr.free.nrw.commons.category.CategoryImagesCallback
 import fr.free.nrw.commons.explore.paging.BasePagingFragment
+import fr.free.nrw.commons.media.MediaDetailPagerFragment.MediaDetailProvider
 import kotlinx.android.synthetic.main.fragment_search_paginated.*
 
 
-abstract class PageableMediaFragment : BasePagingFragment<Media>() {
+abstract class PageableMediaFragment : BasePagingFragment<Media>(), MediaDetailProvider {
-    override val pagedListAdapter by lazy { PagedMediaAdapter(::onItemClicked) }
+
+    override val pagedListAdapter by lazy {
+        PagedMediaAdapter {
+            categoryImagesCallback.onMediaClicked(it)
+        }
+    }
 
     override val errorTextId: Int = R.string.error_loading_images
 
     override fun getEmptyText(query: String) = getString(R.string.no_images_found)
 
-    protected abstract fun onItemClicked(position: Int)
+    lateinit var categoryImagesCallback: CategoryImagesCallback
 
-    protected abstract fun notifyViewPager()
+    override fun onAttach(context: Context) {
+        super.onAttach(context)
+        categoryImagesCallback = (context as CategoryImagesCallback)
+    }
 
-    private val simpleDataObserver = SimpleDataObserver { notifyViewPager() }
+    private val simpleDataObserver = SimpleDataObserver {
+        categoryImagesCallback.viewPagerNotifyDataSetChanged()
+    }
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
@@ -31,12 +44,12 @@ abstract class PageableMediaFragment : BasePagingFragment<Media>() {
         pagedListAdapter.unregisterAdapterDataObserver(simpleDataObserver)
     }
 
-    fun getMediaAtPosition(position: Int): Media? =
+    override fun getMediaAtPosition(position: Int): Media? =
         pagedListAdapter.currentList?.get(position)?.takeIf { it.filename != null }
             .also {
                 pagedListAdapter.currentList?.loadAround(position)
                 paginatedSearchResultsList.scrollToPosition(position)
             }
 
-    fun getTotalMediaCount(): Int = pagedListAdapter.itemCount
+    override fun getTotalMediaCount(): Int = pagedListAdapter.itemCount
 }

app/src/main/java/fr/free/nrw/commons/explore/media/SearchMediaFragment.kt

@@ -1,26 +1,15 @@
 package fr.free.nrw.commons.explore.media
 
-import fr.free.nrw.commons.category.CategoryImagesCallback
-import fr.free.nrw.commons.explore.SearchActivity
 import javax.inject.Inject
 
 /**
  * Displays the image search screen.
  */
-class SearchMediaFragment : PageableMediaFragment(){
+class SearchMediaFragment : PageableMediaFragment() {
     @Inject
     lateinit var presenter: SearchMediaFragmentPresenter
 
     override val injectedPresenter
         get() = presenter
-
-    override fun onItemClicked(position: Int) {
-        (context as SearchActivity).onSearchImageClicked(position)
-    }
-
-    override fun notifyViewPager() {
-        (activity as CategoryImagesCallback).viewPagerNotifyDataSetChanged()
-    }
-
 }
 

app/src/main/java/fr/free/nrw/commons/media/MediaClient.kt

@@ -211,5 +211,6 @@ class MediaClient @Inject constructor(
 
     fun resetCategoryContinuation(category: String) {
         continuationExists.remove("$CATEGORY_CONTINUATION_PREFIX$category")
+        continuationStore.remove("$CATEGORY_CONTINUATION_PREFIX$category")
     }
 }

app/src/test/kotlin/fr/free/nrw/commons/category/CategoriesModelTest.kt

@@ -4,9 +4,8 @@ import categoryItem
 import com.nhaarman.mockitokotlin2.mock
 import com.nhaarman.mockitokotlin2.whenever
 import depictedItem
-import fr.free.nrw.commons.explore.depictions.DepictsClient
 import fr.free.nrw.commons.upload.GpsCategoryModel
-import io.reactivex.Observable
+import io.reactivex.Single
 import io.reactivex.subjects.BehaviorSubject
 import org.junit.Before
 import org.junit.Test
@@ -35,7 +34,7 @@ class CategoriesModelTest {
 
         val expectedList = listOf("Test")
         whenever(categoryClient.searchCategoriesForPrefix("tes", 25))
-            .thenReturn(Observable.just(expectedList))
+            .thenReturn(Single.just(expectedList))
 
         // Checking if both return "Test"
         val expectedItems = expectedList.map { CategoryItem(it, false) }
@@ -56,7 +55,7 @@ class CategoriesModelTest {
         whenever(gpsCategoryModel.categoriesFromLocation)
             .thenReturn(BehaviorSubject.createDefault(listOf("gpsCategory")))
         whenever(categoryClient.searchCategories("tes", 25))
-            .thenReturn(Observable.just(listOf("titleSearch")))
+            .thenReturn(Single.just(listOf("titleSearch")))
         whenever(categoryDao.recentCategories(25)).thenReturn(listOf("recentCategories"))
         CategoriesModel(categoryClient, categoryDao, gpsCategoryModel)
             .searchAll("", listOf("tes"), listOf(depictedItem))

app/src/test/kotlin/fr/free/nrw/commons/category/CategoryClientTest.kt

@@ -2,11 +2,10 @@ package fr.free.nrw.commons.category
 
 import com.nhaarman.mockitokotlin2.mock
 import com.nhaarman.mockitokotlin2.whenever
-import io.reactivex.Observable
+import io.reactivex.Single
 import org.junit.Before
 import org.junit.Test
-import org.mockito.ArgumentMatchers.anyInt
+import org.mockito.ArgumentMatchers.*
-import org.mockito.ArgumentMatchers.anyString
 import org.mockito.InjectMocks
 import org.mockito.Mock
 import org.mockito.Mockito.mock
@@ -32,7 +31,7 @@ class CategoryClientTest {
     fun searchCategoriesFound() {
         val mockResponse = withMockResponse("Category:Test")
         whenever(categoryInterface.searchCategories(anyString(), anyInt(), anyInt()))
-            .thenReturn(Observable.just(mockResponse))
+            .thenReturn(Single.just(mockResponse))
         categoryClient.searchCategories("tes", 10)
             .test()
             .assertValues(listOf("Test"))
@@ -45,7 +44,7 @@ class CategoryClientTest {
     fun searchCategoriesNull() {
         val mockResponse = withNullPages()
         whenever(categoryInterface.searchCategories(anyString(), anyInt(), anyInt()))
-            .thenReturn(Observable.just(mockResponse))
+            .thenReturn(Single.just(mockResponse))
         categoryClient.searchCategories("tes", 10)
             .test()
             .assertValues(emptyList())
@@ -58,7 +57,7 @@ class CategoryClientTest {
     fun searchCategoriesForPrefixFound() {
         val mockResponse = withMockResponse("Category:Test")
         whenever(categoryInterface.searchCategoriesForPrefix(anyString(), anyInt(), anyInt()))
-            .thenReturn(Observable.just(mockResponse))
+            .thenReturn(Single.just(mockResponse))
         categoryClient.searchCategoriesForPrefix("tes", 10)
             .test()
             .assertValues(listOf("Test"))
@@ -71,7 +70,7 @@ class CategoryClientTest {
     fun searchCategoriesForPrefixNull() {
         val mockResponse = withNullPages()
         whenever(categoryInterface.searchCategoriesForPrefix(anyString(), anyInt(), anyInt()))
-            .thenReturn(Observable.just(mockResponse))
+            .thenReturn(Single.just(mockResponse))
         categoryClient.searchCategoriesForPrefix("tes", 10)
             .test()
             .assertValues(emptyList())
@@ -84,7 +83,7 @@ class CategoryClientTest {
     fun getParentCategoryListFound() {
         val mockResponse = withMockResponse("Category:Test")
         whenever(categoryInterface.getParentCategoryList(anyString()))
-            .thenReturn(Observable.just(mockResponse))
+            .thenReturn(Single.just(mockResponse))
         categoryClient.getParentCategoryList("tes")
             .test()
             .assertValues(listOf("Test"))
@@ -94,7 +93,7 @@ class CategoryClientTest {
     fun getParentCategoryListNull() {
         val mockResponse = withNullPages()
         whenever(categoryInterface.getParentCategoryList(anyString()))
-            .thenReturn(Observable.just(mockResponse))
+            .thenReturn(Single.just(mockResponse))
         categoryClient.getParentCategoryList("tes")
             .test()
             .assertValues(emptyList())
@@ -103,8 +102,8 @@ class CategoryClientTest {
     @Test
     fun getSubCategoryListFound() {
         val mockResponse = withMockResponse("Category:Test")
-        whenever(categoryInterface.getSubCategoryList("tes"))
+        whenever(categoryInterface.getSubCategoryList("tes", emptyMap()))
-            .thenReturn(Observable.just(mockResponse))
+            .thenReturn(Single.just(mockResponse))
         categoryClient.getSubCategoryList("tes")
             .test()
             .assertValues(listOf("Test"))
@@ -113,8 +112,11 @@ class CategoryClientTest {
     @Test
     fun getSubCategoryListNull() {
         val mockResponse = withNullPages()
-        whenever(categoryInterface.getSubCategoryList(anyString()))
+        whenever(categoryInterface.getSubCategoryList(
-            .thenReturn(Observable.just(mockResponse))
+            anyString(),
+            anyMap()
+        ))
+            .thenReturn(Single.just(mockResponse))
         categoryClient.getSubCategoryList("tes")
             .test()
             .assertValues(emptyList())

app/src/test/kotlin/fr/free/nrw/commons/explore/categories/sub/PageableSubCategoriesDataSourceTest.kt

@@ -0,0 +1,48 @@
+package fr.free.nrw.commons.explore.categories.sub
+
+import com.nhaarman.mockitokotlin2.never
+import com.nhaarman.mockitokotlin2.verify
+import com.nhaarman.mockitokotlin2.whenever
+import fr.free.nrw.commons.category.CategoryClient
+import fr.free.nrw.commons.explore.paging.LiveDataConverter
+import io.reactivex.Single
+import org.hamcrest.CoreMatchers.`is`
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.Before
+import org.junit.Test
+import org.mockito.Mock
+import org.mockito.MockitoAnnotations
+
+class PageableSubCategoriesDataSourceTest{
+    @Mock
+    lateinit var categoryClient: CategoryClient
+    @Mock
+    lateinit var liveDataConverter: LiveDataConverter
+
+    @Before
+    fun setUp() {
+        MockitoAnnotations.initMocks(this)
+    }
+
+    @Test
+    fun `loadFunction calls reset at position 0`() {
+        val dataSource =
+            PageableSubCategoriesDataSource(liveDataConverter, categoryClient)
+        dataSource.onQueryUpdated("test")
+        whenever(categoryClient.getSubCategoryList("test"))
+            .thenReturn(Single.just(emptyList()))
+        assertThat(dataSource.loadFunction(-1, 0), `is`(emptyList()))
+        verify(categoryClient).resetSubCategoryContinuation("test")
+    }
+
+    @Test
+    fun `loadFunction does not call reset at any other position`() {
+        val dataSource =
+            PageableSubCategoriesDataSource(liveDataConverter, categoryClient)
+        dataSource.onQueryUpdated("test")
+        whenever(categoryClient.getSubCategoryList("test"))
+            .thenReturn(Single.just(emptyList()))
+        assertThat(dataSource.loadFunction(-1, 1), `is`(emptyList()))
+        verify(categoryClient, never()).resetSubCategoryContinuation("test")
+    }
+}

app/src/test/kotlin/fr/free/nrw/commons/explore/categroies/PageableCategoriesDataSourceTest.kt

@@ -4,7 +4,7 @@ import com.nhaarman.mockitokotlin2.mock
 import com.nhaarman.mockitokotlin2.whenever
 import fr.free.nrw.commons.category.CategoryClient
 import fr.free.nrw.commons.explore.categories.search.PageableCategoriesDataSource
-import io.reactivex.Observable
+import io.reactivex.Single
 import org.hamcrest.MatcherAssert.assertThat
 import org.hamcrest.Matchers
 import org.junit.Test
@@ -14,7 +14,7 @@ class PageableCategoriesDataSourceTest {
     fun `loadFunction loads categories`() {
         val categoryClient: CategoryClient = mock()
         whenever(categoryClient.searchCategories("test", 0, 1))
-            .thenReturn(Observable.just(emptyList()))
+            .thenReturn(Single.just(emptyList()))
         val pageableCategoriesDataSource = PageableCategoriesDataSource(mock(), categoryClient)
         pageableCategoriesDataSource.onQueryUpdated("test")
         assertThat(pageableCategoriesDataSource.loadFunction(0, 1), Matchers.`is`(emptyList()))