Swapped the ListView for a RecyclerView, made the fragment cleaner and fixed a whole bunch of code inspection issues.

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

@@ -1,67 +0,0 @@
-package fr.free.nrw.commons.category;
-
-
-import android.content.Context;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.BaseAdapter;
-import android.widget.CheckedTextView;
-
-import java.util.ArrayList;
-
-import fr.free.nrw.commons.R;
-
-public class CategoriesAdapter extends BaseAdapter {
-
-    private LayoutInflater mInflater;
-
-    private ArrayList<CategorizationFragment.CategoryItem> items;
-
-    public CategoriesAdapter(Context context, ArrayList<CategorizationFragment.CategoryItem> items) {
-        this.items = items;
-        mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
-    }
-
-    @Override
-    public int getCount() {
-        return items.size();
-    }
-
-    @Override
-    public Object getItem(int i) {
-        return items.get(i);
-    }
-
-    public ArrayList<CategorizationFragment.CategoryItem> getItems() {
-        return items;
-    }
-
-    public void setItems(ArrayList<CategorizationFragment.CategoryItem> items) {
-        this.items = items;
-    }
-
-    @Override
-    public long getItemId(int i) {
-        return i;
-    }
-
-    @Override
-    public View getView(int i, View view, ViewGroup viewGroup) {
-        CheckedTextView checkedView;
-
-        if(view == null) {
-            checkedView = (CheckedTextView) mInflater.inflate(R.layout.layout_categories_item, null);
-
-        } else {
-            checkedView = (CheckedTextView) view;
-        }
-
-        CategorizationFragment.CategoryItem item = (CategorizationFragment.CategoryItem) this.getItem(i);
-        checkedView.setChecked(item.selected);
-        checkedView.setText(item.name);
-        checkedView.setTag(i);
-
-        return checkedView;
-    }
-}

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

@@ -0,0 +1,24 @@
+package fr.free.nrw.commons.category;
+
+import com.pedrogomez.renderers.ListAdapteeCollection;
+import com.pedrogomez.renderers.RVRendererAdapter;
+import com.pedrogomez.renderers.RendererBuilder;
+
+import java.util.Collections;
+import java.util.List;
+
+class CategoriesAdapterFactory {
+    private final CategoriesRenderer.CategoryClickedListener listener;
+
+    CategoriesAdapterFactory(CategoriesRenderer.CategoryClickedListener listener) {
+        this.listener = listener;
+    }
+
+    public RVRendererAdapter<CategoryItem> create(List<CategoryItem> placeList) {
+        RendererBuilder<CategoryItem> builder = new RendererBuilder<CategoryItem>()
+                .bind(CategoryItem.class, new CategoriesRenderer(listener));
+        ListAdapteeCollection<CategoryItem> collection = new ListAdapteeCollection<>(
+                placeList != null ? placeList : Collections.<CategoryItem>emptyList());
+        return new RVRendererAdapter<>(builder, collection);
+    }
+}

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

@@ -0,0 +1,57 @@
+package fr.free.nrw.commons.category;
+
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.CheckedTextView;
+
+import com.pedrogomez.renderers.Renderer;
+
+import butterknife.BindView;
+import butterknife.ButterKnife;
+import fr.free.nrw.commons.R;
+
+class CategoriesRenderer extends Renderer<CategoryItem> {
+    @BindView(R.id.tvName) CheckedTextView checkedView;
+    private final CategoryClickedListener listener;
+
+    CategoriesRenderer(CategoryClickedListener listener) {
+        this.listener = listener;
+    }
+
+    @Override
+    protected View inflate(LayoutInflater layoutInflater, ViewGroup viewGroup) {
+        return layoutInflater.inflate(R.layout.layout_categories_item, viewGroup, false);
+    }
+
+    @Override
+    protected void setUpView(View view) {
+        ButterKnife.bind(this, view);
+    }
+
+    @Override
+    protected void hookListeners(View view) {
+        view.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                CategoryItem item = getContent();
+                item.selected = !item.selected;
+                checkedView.setChecked(item.selected);
+                if (listener != null) {
+                    listener.categoryClicked(item);
+                }
+            }
+        });
+    }
+
+    @Override
+    public void render() {
+        CategoryItem item = getContent();
+        checkedView.setChecked(item.selected);
+        checkedView.setText(item.name);
+    }
+
+    interface CategoryClickedListener {
+        void categoryClicked(CategoryItem item);
+    }
+}

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

@@ -6,12 +6,12 @@ import android.content.SharedPreferences;
 import android.database.Cursor;
 import android.os.AsyncTask;
 import android.os.Bundle;
-import android.os.Parcel;
-import android.os.Parcelable;
 import android.os.RemoteException;
 import android.preference.PreferenceManager;
 import android.support.v4.app.Fragment;
 import android.support.v7.app.AlertDialog;
+import android.support.v7.widget.LinearLayoutManager;
+import android.support.v7.widget.RecyclerView;
 import android.text.Editable;
 import android.text.TextUtils;
 import android.text.TextWatcher;
@@ -22,15 +22,14 @@ import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
-import android.widget.AdapterView;
-import android.widget.CheckedTextView;
 import android.widget.EditText;
-import android.widget.ListView;
 import android.widget.ProgressBar;
 import android.widget.TextView;
 
+import com.pedrogomez.renderers.ListAdapteeCollection;
+import com.pedrogomez.renderers.RVRendererAdapter;
+
 import java.util.ArrayList;
-import java.util.Date;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashSet;
@@ -40,6 +39,8 @@ import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
+import butterknife.BindView;
+import butterknife.ButterKnife;
 import fr.free.nrw.commons.R;
 import fr.free.nrw.commons.upload.MwVolleyApi;
 import timber.log.Timber;
@@ -47,83 +48,180 @@ import timber.log.Timber;
 /**
  * Displays the category suggestion and selection screen. Category search is initiated here.
  */
-public class CategorizationFragment extends Fragment {
+public class CategorizationFragment extends Fragment implements CategoriesRenderer.CategoryClickedListener {
-    public interface OnCategoriesSaveHandler {
+    public static final int SEARCH_CATS_LIMIT = 25;
-        void onCategoriesSave(ArrayList<String> categories);
-    }
 
-    ListView categoriesList;
+    @BindView(R.id.categoriesListBox) RecyclerView categoriesList;
-    protected EditText categoriesFilter;
+    @BindView(R.id.categoriesSearchBox) EditText categoriesFilter;
-    ProgressBar categoriesSearchInProgress;
+    @BindView(R.id.categoriesSearchInProgress) ProgressBar categoriesSearchInProgress;
-    TextView categoriesNotFoundView;
+    @BindView(R.id.categoriesNotFound) TextView categoriesNotFoundView;
-    TextView categoriesSkip;
+    @BindView(R.id.categoriesExplanation) TextView categoriesSkip;
-    private CategoryTextWatcher textWatcher = new CategoryTextWatcher();
-
-    CategoriesAdapter categoriesAdapter;
-    ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
 
+    private RVRendererAdapter<CategoryItem> categoriesAdapter;
     private OnCategoriesSaveHandler onCategoriesSaveHandler;
-
+    private HashMap<String, ArrayList<String>> categoriesCache;
-    protected HashMap<String, ArrayList<String>> categoriesCache;
-
     private ArrayList<String> selectedCategories = new ArrayList<>();
-
+    private ContentProviderClient client;
+    private PrefixUpdater prefixUpdaterSub;
+    private MethodAUpdater methodAUpdaterSub;
+    private final CategoryTextWatcher textWatcher = new CategoryTextWatcher();
+    private final CategoriesAdapterFactory adapterFactory = new CategoriesAdapterFactory(this);
+    private final ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
+    private final ArrayList<String> titleCatItems = new ArrayList<>();
+    private final CountDownLatch mergeLatch = new CountDownLatch(1);
     // LHS guarantees ordered insertions, allowing for prioritized method A results
     private final Set<String> results = new LinkedHashSet<>();
-    PrefixUpdater prefixUpdaterSub;
-    MethodAUpdater methodAUpdaterSub;
 
-    private final ArrayList<String> titleCatItems = new ArrayList<>();
+    @SuppressWarnings("unchecked")
-    final CountDownLatch mergeLatch = new CountDownLatch(1);
+    @Override
+    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+        View rootView = inflater.inflate(R.layout.fragment_categorization, container, false);
+        ButterKnife.bind(this, rootView);
 
-    private ContentProviderClient client;
+        categoriesList.setLayoutManager(new LinearLayoutManager(getContext()));
 
-    protected final static int SEARCH_CATS_LIMIT = 25;
+        categoriesSkip.setOnClickListener(new View.OnClickListener() {
-
-    public static class CategoryItem implements Parcelable {
-        public String name;
-        public boolean selected;
-
-        public static Creator<CategoryItem> CREATOR = new Creator<CategoryItem>() {
             @Override
-            public CategoryItem createFromParcel(Parcel parcel) {
+            public void onClick(View view) {
-                return new CategoryItem(parcel);
+                getActivity().onBackPressed();
+                getActivity().finish();
             }
+        });
 
-            @Override
+        ArrayList<CategoryItem> items;
-            public CategoryItem[] newArray(int i) {
+        if (savedInstanceState == null) {
-                return new CategoryItem[0];
+            items = new ArrayList<>();
-            }
+            categoriesCache = new HashMap<>();
-        };
+        } else {
-
+            items = savedInstanceState.getParcelableArrayList("currentCategories");
-        public CategoryItem(String name, boolean selected) {
+            categoriesCache = (HashMap<String, ArrayList<String>>) savedInstanceState.getSerializable("categoriesCache");
-            this.name = name;
-            this.selected = selected;
         }
 
-        public CategoryItem(Parcel in) {
+        categoriesAdapter = adapterFactory.create(items);
-            name = in.readString();
+        categoriesList.setAdapter(categoriesAdapter);
-            selected = in.readInt() == 1;
+        categoriesFilter.addTextChangedListener(textWatcher);
-        }
 
-        @Override
+        startUpdatingCategoryList();
-        public int describeContents() {
-            return 0;
-        }
 
-        @Override
+        return rootView;
-        public void writeToParcel(Parcel parcel, int flags) {
+    }
-            parcel.writeString(name);
+
-            parcel.writeInt(selected ? 1 : 0);
+    @Override
+    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+        menu.clear();
+        inflater.inflate(R.menu.fragment_categorization, menu);
+    }
+
+    @Override
+    public void onResume() {
+        super.onResume();
+
+        View rootView = getView();
+        if (rootView != null) {
+            rootView.setFocusableInTouchMode(true);
+            rootView.requestFocus();
+            rootView.setOnKeyListener(new View.OnKeyListener() {
+                @Override
+                public boolean onKey(View v, int keyCode, KeyEvent event) {
+                    if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK) {
+                        backButtonDialog();
+                        return true;
+                    }
+                    return false;
+                }
+            });
         }
     }
 
+    @Override
+    public void onDestroyView() {
+        categoriesFilter.removeTextChangedListener(textWatcher);
+        super.onDestroyView();
+    }
+
+    @Override
+    public void onDestroy() {
+        super.onDestroy();
+        client.release();
+    }
+
+    @Override
+    public void onSaveInstanceState(Bundle outState) {
+        super.onSaveInstanceState(outState);
+        int itemCount = categoriesAdapter.getItemCount();
+        ArrayList<CategoryItem> items = new ArrayList<>(itemCount);
+        for (int i = 0; i < itemCount; i++) {
+            items.add(categoriesAdapter.getItem(i));
+        }
+        outState.putParcelableArrayList("currentCategories", items);
+        outState.putSerializable("categoriesCache", categoriesCache);
+    }
+
+    @Override
+    public boolean onOptionsItemSelected(MenuItem menuItem) {
+        switch (menuItem.getItemId()) {
+            case R.id.menu_save_categories:
+
+                int numberSelected = 0;
+
+                selectedCategories = new ArrayList<>();
+                int count = categoriesAdapter.getItemCount();
+                for (int i = 0; i < count; i++) {
+                    CategoryItem item = categoriesAdapter.getItem(i);
+                    if (item.selected) {
+                        selectedCategories.add(item.name);
+                        numberSelected++;
+                    }
+                }
+
+                //If no categories selected, display warning to user
+                if (numberSelected == 0) {
+                    new AlertDialog.Builder(getActivity())
+                            .setMessage("Images without categories are rarely usable. Are you sure you want to submit without selecting categories?")
+                            .setTitle("No Categories Selected")
+                            .setPositiveButton("No, go back", new DialogInterface.OnClickListener() {
+                                @Override
+                                public void onClick(DialogInterface dialog, int id) {
+                                    //Exit menuItem so user can select their categories
+                                }
+                            })
+                            .setNegativeButton("Yes, submit", new DialogInterface.OnClickListener() {
+                                @Override
+                                public void onClick(DialogInterface dialog, int id) {
+                                    //Proceed to submission
+                                    onCategoriesSaveHandler.onCategoriesSave(selectedCategories);
+                                }
+                            })
+                            .create()
+                            .show();
+                } else {
+                    //Proceed to submission
+                    onCategoriesSaveHandler.onCategoriesSave(selectedCategories);
+                    return true;
+                }
+        }
+        return super.onOptionsItemSelected(menuItem);
+    }
+
+    @Override
+    public void onActivityCreated(Bundle savedInstanceState) {
+        super.onActivityCreated(savedInstanceState);
+        setHasOptionsMenu(true);
+        onCategoriesSaveHandler = (OnCategoriesSaveHandler) getActivity();
+        getActivity().setTitle(R.string.categories_activity_title);
+        client = getActivity().getContentResolver().acquireContentProviderClient(CategoryContentProvider.AUTHORITY);
+    }
+
+    public HashMap<String, ArrayList<String>> getCategoriesCache() {
+        return categoriesCache;
+    }
+
     /**
      * Retrieves category suggestions from title input
+     *
      * @return a list containing title-related categories
      */
-    protected ArrayList<String> titleCatQuery() {
+    private ArrayList<String> titleCatQuery() {
-
         TitleCategories titleCategoriesSub;
 
         //Retrieve the title that was saved when user tapped submit icon
@@ -157,37 +255,41 @@ public class CategorizationFragment extends Fragment {
 
     /**
      * Retrieves recently-used categories
+     *
      * @return a list containing recent categories
      */
-    protected ArrayList<String> recentCatQuery() {
+    private ArrayList<String> recentCatQuery() {
         ArrayList<String> items = new ArrayList<>();
-
+        Cursor cursor = null;
         try {
-            Cursor cursor = client.query(
+            cursor = client.query(
                     CategoryContentProvider.BASE_URI,
                     Category.Table.ALL_FIELDS,
                     null,
                     new String[]{},
                     Category.Table.COLUMN_LAST_USED + " DESC");
             // fixme add a limit on the original query instead of falling out of the loop?
-            while (cursor.moveToNext() && cursor.getPosition() < SEARCH_CATS_LIMIT) {
+            while (cursor != null && cursor.moveToNext()
+                    && cursor.getPosition() < SEARCH_CATS_LIMIT) {
                 Category cat = Category.fromCursor(cursor);
                 items.add(cat.getName());
             }
-            cursor.close();
+        } catch (RemoteException e) {
-        }
-        catch (RemoteException e) {
             throw new RuntimeException(e);
+        } finally {
+            if (cursor != null) {
+                cursor.close();
+            }
         }
         return items;
     }
 
     /**
      * Merges nearby categories, categories suggested based on title, and recent categories... without duplicates.
+     *
      * @return a list containing merged categories
      */
-    protected ArrayList<String> mergeItems() {
+    ArrayList<String> mergeItems() {
-
         Set<String> mergedItems = new LinkedHashSet<>();
 
         Timber.d("Calling APIs for GPS cats, title cats and recent cats...");
@@ -213,7 +315,7 @@ public class CategorizationFragment extends Fragment {
         Timber.d("Adding title items: %s", titleItems);
         mergedItems.addAll(recentItems);
         Timber.d("Adding recent items: %s", recentItems);
-        
+
         //Needs to be an ArrayList and not a List unless we want to modify a big portion of preexisting code
         ArrayList<String> mergedItemsList = new ArrayList<>(mergedItems);
 
@@ -223,15 +325,17 @@ public class CategorizationFragment extends Fragment {
 
     /**
      * Displays categories found to the user as they type in the search box
+     *
      * @param categories a list of all categories found for the search string
-     * @param filter the search string
+     * @param filter     the search string
      */
-    protected void setCatsAfterAsync(ArrayList<String> categories, String filter) {
+    private void setCatsAfterAsync(ArrayList<String> categories, String filter) {
-
         if (getActivity() != null) {
             ArrayList<CategoryItem> items = new ArrayList<>();
             HashSet<String> existingKeys = new HashSet<>();
-            for (CategoryItem item : categoriesAdapter.getItems()) {
+            int count = categoriesAdapter.getItemCount();
+            for (int i = 0; i < count; i++) {
+                CategoryItem item = categoriesAdapter.getItem(i);
                 if (item.selected) {
                     items.add(item);
                     existingKeys.add(item.name);
@@ -243,8 +347,8 @@ public class CategorizationFragment extends Fragment {
                 }
             }
 
-            categoriesAdapter.setItems(items);
+            categoriesAdapter.setCollection(new ListAdapteeCollection<>(items));
-            categoriesAdapter.notifyDataSetInvalidated();
+            categoriesAdapter.notifyDataSetChanged();
             categoriesSearchInProgress.setVisibility(View.GONE);
 
             if (categories.isEmpty()) {
@@ -258,8 +362,7 @@ public class CategorizationFragment extends Fragment {
             } else {
                 categoriesList.smoothScrollToPosition(existingKeys.size());
             }
-        }
+        } else {
-        else {
             Timber.e("Error: Fragment is null");
         }
     }
@@ -272,7 +375,6 @@ public class CategorizationFragment extends Fragment {
      * above Prefix results.
      */
     private void requestSearchResults() {
-
         final CountDownLatch latch = new CountDownLatch(1);
 
         prefixUpdaterSub = new PrefixUpdater(this) {
@@ -282,8 +384,7 @@ public class CategorizationFragment extends Fragment {
                 try {
                     result = super.doInBackground();
                     latch.await();
-                }
+                } catch (InterruptedException e) {
-                catch (InterruptedException e) {
                     Timber.w(e);
                     //Thread.currentThread().interrupt();
                 }
@@ -325,7 +426,6 @@ public class CategorizationFragment extends Fragment {
     }
 
     private void startUpdatingCategoryList() {
-
         if (prefixUpdaterSub != null) {
             prefixUpdaterSub.cancel(true);
         }
@@ -339,238 +439,41 @@ public class CategorizationFragment extends Fragment {
 
     public int getCurrentSelectedCount() {
         int count = 0;
-        for(CategoryItem item: categoriesAdapter.getItems()) {
+        int numberOfItems = categoriesAdapter.getItemCount();
-            if(item.selected) {
+        for (int i = 0; i < numberOfItems; i++) {
+            CategoryItem item = categoriesAdapter.getItem(i);
+            if (item.selected) {
                 count++;
             }
         }
         return count;
     }
 
-    private Category lookupCategory(String name) {
-        Cursor cursor = null;
-        try {
-            cursor = client.query(
-                    CategoryContentProvider.BASE_URI,
-                    Category.Table.ALL_FIELDS,
-                    Category.Table.COLUMN_NAME + "=?",
-                    new String[] {name},
-                    null);
-            if (cursor.moveToFirst()) {
-                return Category.fromCursor(cursor);
-            }
-        } catch (RemoteException e) {
-            // This feels lazy, but to hell with checked exceptions. :)
-            throw new RuntimeException(e);
-        } finally {
-            if ( cursor != null ) {
-                cursor.close();
-            }
-        }
-
-        // Newly used category...
-        Category cat = new Category();
-        cat.setName(name);
-        cat.setLastUsed(new Date());
-        cat.setTimesUsed(0);
-        return cat;
-    }
-
-    private class CategoryCountUpdater extends AsyncTask<Void, Void, Void> {
-
-        private String name;
-
-        public CategoryCountUpdater(String name) {
-            this.name = name;
-        }
-
-        @Override
-        protected Void doInBackground(Void... voids) {
-            Category cat = lookupCategory(name);
-            cat.incTimesUsed();
-
-            cat.setContentProviderClient(client);
-            cat.save();
-
-            return null; // Make the compiler happy.
-        }
-    }
-
-    private void updateCategoryCount(String name) {
-        new CategoryCountUpdater(name).executeOnExecutor(executor);
-    }
-
-    @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
-        View rootView = inflater.inflate(R.layout.fragment_categorization, null);
-        categoriesList = (ListView) rootView.findViewById(R.id.categoriesListBox);
-        categoriesFilter = (EditText) rootView.findViewById(R.id.categoriesSearchBox);
-        categoriesSearchInProgress = (ProgressBar) rootView.findViewById(R.id.categoriesSearchInProgress);
-        categoriesNotFoundView = (TextView) rootView.findViewById(R.id.categoriesNotFound);
-        categoriesSkip = (TextView) rootView.findViewById(R.id.categoriesExplanation);
-
-        categoriesSkip.setOnClickListener(new View.OnClickListener() {
-            @Override
-            public void onClick(View view) {
-                getActivity().onBackPressed();
-                getActivity().finish();
-            }
-        });
-
-        ArrayList<CategoryItem> items;
-        if(savedInstanceState == null) {
-            items = new ArrayList<>();
-            categoriesCache = new HashMap<>();
-        } else {
-            items = savedInstanceState.getParcelableArrayList("currentCategories");
-            categoriesCache = (HashMap<String, ArrayList<String>>) savedInstanceState.getSerializable("categoriesCache");
-        }
-
-        categoriesAdapter = new CategoriesAdapter(getActivity(), items);
-        categoriesList.setAdapter(categoriesAdapter);
-
-        categoriesList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
-            @Override
-            public void onItemClick(AdapterView<?> adapterView, View view, int index, long id) {
-                CheckedTextView checkedView = (CheckedTextView) view;
-                CategoryItem item = (CategoryItem) adapterView.getAdapter().getItem(index);
-                item.selected = !item.selected;
-                checkedView.setChecked(item.selected);
-                if (item.selected) {
-                    updateCategoryCount(item.name);
-                }
-            }
-        });
-
-        categoriesFilter.addTextChangedListener(textWatcher);
-
-        startUpdatingCategoryList();
-
-        return rootView;
-    }
-
-    @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
-        menu.clear();
-        inflater.inflate(R.menu.fragment_categorization, menu);
-    }
-
-    @Override
-    public void onResume() {
-        super.onResume();
-
-        View rootView = getView();
-        if (rootView != null) {
-            rootView.setFocusableInTouchMode(true);
-            rootView.requestFocus();
-            rootView.setOnKeyListener(new View.OnKeyListener() {
-                @Override
-                public boolean onKey(View v, int keyCode, KeyEvent event) {
-                    if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK) {
-                        backButtonDialog();
-                        return true;
-                    }
-                    return false;
-                }
-            });
-        }
-    }
-
-    @Override
-    public void onDestroyView() {
-        categoriesFilter.removeTextChangedListener(textWatcher);
-        super.onDestroyView();
-    }
-
     public void backButtonDialog() {
-        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+        new AlertDialog.Builder(getActivity())
-
+                .setMessage("Are you sure you want to go back? The image will not have any categories saved.")
-        builder.setMessage("Are you sure you want to go back? The image will not have any categories saved.")
+                .setTitle("Warning")
-                .setTitle("Warning");
+                .setPositiveButton("No", new DialogInterface.OnClickListener() {
-        builder.setPositiveButton("No", new DialogInterface.OnClickListener() {
+                    @Override
-            @Override
+                    public void onClick(DialogInterface dialog, int id) {
-            public void onClick(DialogInterface dialog, int id) {
+                        //No need to do anything, user remains on categorization screen
-                //No need to do anything, user remains on categorization screen
-            }
-        });
-        builder.setNegativeButton("Yes", new DialogInterface.OnClickListener() {
-            @Override
-            public void onClick(DialogInterface dialog, int id) {
-                getActivity().finish();
-            }
-        });
-
-        AlertDialog dialog = builder.create();
-        dialog.show();
-    }
-
-    @Override
-    public void onDestroy() {
-        super.onDestroy();
-        client.release();
-    }
-
-    @Override
-    public void onSaveInstanceState(Bundle outState) {
-        super.onSaveInstanceState(outState);
-        outState.putParcelableArrayList("currentCategories", categoriesAdapter.getItems());
-        outState.putSerializable("categoriesCache", categoriesCache);
-    }
-
-    @Override
-    public boolean onOptionsItemSelected(MenuItem menuItem) {
-        switch(menuItem.getItemId()) {
-            case R.id.menu_save_categories:
-
-                int numberSelected = 0;
-
-                for(CategoryItem item: categoriesAdapter.getItems()) {
-                    if(item.selected) {
-                        selectedCategories.add(item.name);
-                        numberSelected++;
                     }
-                }
+                })
-
+                .setNegativeButton("Yes", new DialogInterface.OnClickListener() {
-                //If no categories selected, display warning to user
+                    @Override
-                if (numberSelected == 0) {
+                    public void onClick(DialogInterface dialog, int id) {
-                    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+                        getActivity().finish();
-
+                    }
-                    builder.setMessage("Images without categories are rarely usable. Are you sure you want to submit without selecting categories?")
+                })
-                            .setTitle("No Categories Selected");
+                .create()
-                    builder.setPositiveButton("No, go back", new DialogInterface.OnClickListener() {
+                .show();
-                        @Override
-                        public void onClick(DialogInterface dialog, int id) {
-                            //Exit menuItem so user can select their categories
-                            return;
-                        }
-                    });
-                    builder.setNegativeButton("Yes, submit", new DialogInterface.OnClickListener() {
-                        @Override
-                        public void onClick(DialogInterface dialog, int id) {
-                            //Proceed to submission
-                            onCategoriesSaveHandler.onCategoriesSave(selectedCategories);
-                            return;
-                        }
-                    });
-
-                    AlertDialog dialog = builder.create();
-                    dialog.show();
-                } else {
-                    //Proceed to submission
-                    onCategoriesSaveHandler.onCategoriesSave(selectedCategories);
-                    return true;
-                }
-        }
-        return super.onOptionsItemSelected(menuItem);
     }
 
     @Override
-    public void onActivityCreated(Bundle savedInstanceState) {
+    public void categoryClicked(CategoryItem item) {
-        super.onActivityCreated(savedInstanceState);
+        if (item.selected) {
-        setHasOptionsMenu(true);
+            new CategoryCountUpdater(item.name, client).executeOnExecutor(executor);
-        onCategoriesSaveHandler = (OnCategoriesSaveHandler) getActivity();
+        }
-        getActivity().setTitle(R.string.categories_activity_title);
-        client = getActivity().getContentResolver().acquireContentProviderClient(CategoryContentProvider.AUTHORITY);
     }
 
     private class CategoryTextWatcher implements TextWatcher {

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

@@ -26,7 +26,7 @@ public class Category {
         this.name = name;
     }
 
-    public Date getLastUsed() {
+    private Date getLastUsed() {
         // warning: Date objects are mutable.
         return (Date)lastUsed.clone();
     }
@@ -36,11 +36,11 @@ public class Category {
         this.lastUsed = (Date)lastUsed.clone();
     }
 
-    public void touch() {
+    private void touch() {
         lastUsed = new Date();
     }
 
-    public int getTimesUsed() {
+    private int getTimesUsed() {
         return timesUsed;
     }
 
@@ -70,7 +70,7 @@ public class Category {
         }
     }
 
-    public ContentValues toContentValues() {
+    private ContentValues toContentValues() {
         ContentValues cv = new ContentValues();
         cv.put(Table.COLUMN_NAME, getName());
         cv.put(Table.COLUMN_LAST_USED, getLastUsed().getTime());

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

@@ -7,6 +7,7 @@ import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteQueryBuilder;
 import android.net.Uri;
+import android.support.annotation.NonNull;
 import android.text.TextUtils;
 
 import fr.free.nrw.commons.CommonsApplication;
@@ -41,8 +42,9 @@ public class CategoryContentProvider extends ContentProvider {
         return false;
     }
 
+    @SuppressWarnings("ConstantConditions")
     @Override
-    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
+    public Cursor query(@NonNull Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
         SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
         queryBuilder.setTables(Category.Table.TABLE_NAME);
 
@@ -75,15 +77,16 @@ public class CategoryContentProvider extends ContentProvider {
     }
 
     @Override
-    public String getType(Uri uri) {
+    public String getType(@NonNull Uri uri) {
         return null;
     }
 
+    @SuppressWarnings("ConstantConditions")
     @Override
-    public Uri insert(Uri uri, ContentValues contentValues) {
+    public Uri insert(@NonNull Uri uri, ContentValues contentValues) {
         int uriType = uriMatcher.match(uri);
         SQLiteDatabase sqlDB = dbOpenHelper.getWritableDatabase();
-        long id = 0;
+        long id;
         switch (uriType) {
             case CATEGORIES:
                 id = sqlDB.insert(Category.Table.TABLE_NAME, null, contentValues);
@@ -96,12 +99,13 @@ public class CategoryContentProvider extends ContentProvider {
     }
 
     @Override
-    public int delete(Uri uri, String s, String[] strings) {
+    public int delete(@NonNull Uri uri, String s, String[] strings) {
         return 0;
     }
 
+    @SuppressWarnings("ConstantConditions")
     @Override
-    public int bulkInsert(Uri uri, ContentValues[] values) {
+    public int bulkInsert(@NonNull Uri uri, @NonNull ContentValues[] values) {
         Timber.d("Hello, bulk insert! (CategoryContentProvider)");
         int uriType = uriMatcher.match(uri);
         SQLiteDatabase sqlDB = dbOpenHelper.getWritableDatabase();
@@ -122,8 +126,9 @@ public class CategoryContentProvider extends ContentProvider {
         return values.length;
     }
 
+    @SuppressWarnings("ConstantConditions")
     @Override
-    public int update(Uri uri, ContentValues contentValues, String selection, String[] selectionArgs) {
+    public int update(@NonNull Uri uri, ContentValues contentValues, String selection, String[] selectionArgs) {
         /*
         SQL Injection warnings: First, note that we're not exposing this to the outside world (exported="false")
         Even then, we should make sure to sanitize all user input appropriately. Input that passes through ContentValues
@@ -133,7 +138,7 @@ public class CategoryContentProvider extends ContentProvider {
          */
         int uriType = uriMatcher.match(uri);
         SQLiteDatabase sqlDB = dbOpenHelper.getWritableDatabase();
-        int rowsUpdated = 0;
+        int rowsUpdated;
         switch (uriType) {
             case CATEGORIES_ID:
                 int id = Integer.valueOf(uri.getLastPathSegment());

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

@@ -0,0 +1,59 @@
+package fr.free.nrw.commons.category;
+
+import android.content.ContentProviderClient;
+import android.database.Cursor;
+import android.os.AsyncTask;
+import android.os.RemoteException;
+
+import java.util.Date;
+
+class CategoryCountUpdater extends AsyncTask<Void, Void, Void> {
+
+    private final String name;
+    private final ContentProviderClient client;
+
+    CategoryCountUpdater(String name, ContentProviderClient client) {
+        this.name = name;
+        this.client = client;
+    }
+
+    @Override
+    protected Void doInBackground(Void... voids) {
+        Category cat = lookupCategory(name);
+        cat.incTimesUsed();
+
+        cat.setContentProviderClient(client);
+        cat.save();
+
+        return null; // Make the compiler happy.
+    }
+
+    private Category lookupCategory(String name) {
+        Cursor cursor = null;
+        try {
+            cursor = client.query(
+                    CategoryContentProvider.BASE_URI,
+                    Category.Table.ALL_FIELDS,
+                    Category.Table.COLUMN_NAME + "=?",
+                    new String[]{name},
+                    null);
+            if (cursor != null && cursor.moveToFirst()) {
+                return Category.fromCursor(cursor);
+            }
+        } catch (RemoteException e) {
+            // This feels lazy, but to hell with checked exceptions. :)
+            throw new RuntimeException(e);
+        } finally {
+            if (cursor != null) {
+                cursor.close();
+            }
+        }
+
+        // Newly used category...
+        Category cat = new Category();
+        cat.setName(name);
+        cat.setLastUsed(new Date());
+        cat.setTimesUsed(0);
+        return cat;
+    }
+}

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

@@ -0,0 +1,42 @@
+package fr.free.nrw.commons.category;
+
+import android.os.Parcel;
+import android.os.Parcelable;
+
+class CategoryItem implements Parcelable {
+    public final String name;
+    public boolean selected;
+
+    public static Creator<CategoryItem> CREATOR = new Creator<CategoryItem>() {
+        @Override
+        public CategoryItem createFromParcel(Parcel parcel) {
+            return new CategoryItem(parcel);
+        }
+
+        @Override
+        public CategoryItem[] newArray(int i) {
+            return new CategoryItem[0];
+        }
+    };
+
+    CategoryItem(String name, boolean selected) {
+        this.name = name;
+        this.selected = selected;
+    }
+
+    private CategoryItem(Parcel in) {
+        name = in.readString();
+        selected = in.readInt() == 1;
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    @Override
+    public void writeToParcel(Parcel parcel, int flags) {
+        parcel.writeString(name);
+        parcel.writeInt(selected ? 1 : 0);
+    }
+}

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

@@ -13,6 +13,8 @@ import fr.free.nrw.commons.CommonsApplication;
 import fr.free.nrw.commons.mwapi.MediaWikiApi;
 import timber.log.Timber;
 
+import static fr.free.nrw.commons.category.CategorizationFragment.SEARCH_CATS_LIMIT;
+
 /**
  * Sends asynchronous queries to the Commons MediaWiki API to retrieve categories that are close to
  * the keyword typed in by the user. The 'srsearch' action-specific parameter is used for this
@@ -20,8 +22,8 @@ import timber.log.Timber;
  */
 class MethodAUpdater extends AsyncTask<Void, Void, List<String>> {
 
+    private final CategorizationFragment catFragment;
     private String filter;
-    private CategorizationFragment catFragment;
 
     MethodAUpdater(CategorizationFragment catFragment) {
         this.catFragment = catFragment;
@@ -84,7 +86,7 @@ class MethodAUpdater extends AsyncTask<Void, Void, List<String>> {
 
         //URL https://commons.wikimedia.org/w/api.php?action=query&format=xml&list=search&srwhat=text&srenablerewrites=1&srnamespace=14&srlimit=10&srsearch=
         try {
-            categories = api.searchCategories(CategorizationFragment.SEARCH_CATS_LIMIT, filter);
+            categories = api.searchCategories(SEARCH_CATS_LIMIT, filter);
             Timber.d("Method A URL filter %s", categories);
         } catch (IOException e) {
             Timber.e(e, "IO Exception: ");

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

@@ -0,0 +1,7 @@
+package fr.free.nrw.commons.category;
+
+import java.util.ArrayList;
+
+public interface OnCategoriesSaveHandler {
+    void onCategoriesSave(ArrayList<String> categories);
+}

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

@@ -7,6 +7,7 @@ import android.view.View;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Calendar;
+import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 
@@ -14,18 +15,20 @@ import fr.free.nrw.commons.CommonsApplication;
 import fr.free.nrw.commons.mwapi.MediaWikiApi;
 import timber.log.Timber;
 
+import static fr.free.nrw.commons.category.CategorizationFragment.SEARCH_CATS_LIMIT;
+
 /**
  * Sends asynchronous queries to the Commons MediaWiki API to retrieve categories that share the
  * same prefix as the keyword typed in by the user. The 'acprefix' action-specific parameter is used
  * for this purpose. This class should be subclassed in CategorizationFragment.java to aggregate
  * the results.
  */
-public class PrefixUpdater extends AsyncTask<Void, Void, List<String>> {
+class PrefixUpdater extends AsyncTask<Void, Void, List<String>> {
 
+    private final CategorizationFragment catFragment;
     private String filter;
-    private CategorizationFragment catFragment;
 
-    public PrefixUpdater(CategorizationFragment catFragment) {
+    PrefixUpdater(CategorizationFragment catFragment) {
         this.catFragment = catFragment;
     }
 
@@ -90,8 +93,9 @@ public class PrefixUpdater extends AsyncTask<Void, Void, List<String>> {
         }
 
         //if user types in something that is in cache, return cached category
-        if (catFragment.categoriesCache.containsKey(filter)) {
+        HashMap<String, ArrayList<String>> categoriesCache = catFragment.getCategoriesCache();
-            ArrayList<String> cachedItems = new ArrayList<>(catFragment.categoriesCache.get(filter));
+        if (categoriesCache.containsKey(filter)) {
+            ArrayList<String> cachedItems = new ArrayList<>(categoriesCache.get(filter));
             Timber.d("Found cache items, waiting for filter");
             return new ArrayList<>(filterIrrelevantResults(cachedItems));
         }
@@ -101,7 +105,7 @@ public class PrefixUpdater extends AsyncTask<Void, Void, List<String>> {
         MediaWikiApi api = CommonsApplication.getInstance().getMWApi();
         List<String> categories = new ArrayList<>();
         try {
-            categories = api.allCategories(CategorizationFragment.SEARCH_CATS_LIMIT, this.filter);
+            categories = api.allCategories(SEARCH_CATS_LIMIT, this.filter);
             Timber.d("Prefix URL filter %s", categories);
         } catch (IOException e) {
             Timber.e(e, "IO Exception: ");

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

@@ -19,17 +19,12 @@ class TitleCategories extends AsyncTask<Void, Void, List<String>> {
 
     private final static int SEARCH_CATS_LIMIT = 25;
 
-    private String title;
+    private final String title;
 
     TitleCategories(String title) {
         this.title = title;
     }
 
-    @Override
-    protected void onPreExecute() {
-        super.onPreExecute();
-    }
-
     @Override
     protected List<String> doInBackground(Void... voids) {
 

app/src/main/java/fr/free/nrw/commons/upload/MultipleShareActivity.java

@@ -28,6 +28,7 @@ import fr.free.nrw.commons.Media;
 import fr.free.nrw.commons.R;
 import fr.free.nrw.commons.auth.AuthenticatedActivity;
 import fr.free.nrw.commons.category.CategorizationFragment;
+import fr.free.nrw.commons.category.OnCategoriesSaveHandler;
 import fr.free.nrw.commons.contributions.Contribution;
 import fr.free.nrw.commons.media.MediaDetailPagerFragment;
 import fr.free.nrw.commons.modifications.CategoryModifier;
@@ -43,7 +44,7 @@ public  class       MultipleShareActivity
                     AdapterView.OnItemClickListener,
                     FragmentManager.OnBackStackChangedListener,
                     MultipleUploadListFragment.OnMultipleUploadInitiatedHandler,
-        CategorizationFragment.OnCategoriesSaveHandler {
+        OnCategoriesSaveHandler {
     private CommonsApplication app;
     private ArrayList<Contribution> photosList = null;
 

app/src/main/java/fr/free/nrw/commons/upload/ShareActivity.java

@@ -36,6 +36,7 @@ import fr.free.nrw.commons.R;
 import fr.free.nrw.commons.Utils;
 import fr.free.nrw.commons.auth.AuthenticatedActivity;
 import fr.free.nrw.commons.category.CategorizationFragment;
+import fr.free.nrw.commons.category.OnCategoriesSaveHandler;
 import fr.free.nrw.commons.contributions.Contribution;
 import fr.free.nrw.commons.modifications.CategoryModifier;
 import fr.free.nrw.commons.modifications.ModificationsContentProvider;
@@ -51,7 +52,7 @@ import timber.log.Timber;
 public  class       ShareActivity
         extends     AuthenticatedActivity
         implements  SingleUploadFragment.OnUploadActionInitiated,
-        CategorizationFragment.OnCategoriesSaveHandler {
+        OnCategoriesSaveHandler {
 
     private static final int REQUEST_PERM_ON_CREATE_STORAGE = 1;
     private static final int REQUEST_PERM_ON_CREATE_LOCATION = 2;

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

@@ -60,7 +60,7 @@
         android:visibility="gone"
         />
 
-    <ListView
+    <android.support.v7.widget.RecyclerView
         android:id="@+id/categoriesListBox"
         android:layout_height="wrap_content"
         android:layout_width="match_parent"

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

@@ -1,12 +1,12 @@
 <?xml version="1.0" encoding="utf-8"?>
 <CheckedTextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/tvName"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
-    android:padding="4dp"
     android:checkMark="?android:attr/textCheckMark"
     android:checked="false"
     android:gravity="center_vertical"
-    android:theme="@style/DarkAppTheme"
+    android:padding="4dp"
-    >
+    android:theme="@style/DarkAppTheme">
 
 </CheckedTextView>