Created a new SectionedRecyclerViewAdapter.

src/org/thoughtcrime/securesms/mediapreview/MediaRailAdapter.java

@@ -11,7 +11,7 @@ import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.components.ThumbnailView;
 import org.thoughtcrime.securesms.mediasend.Media;
 import org.thoughtcrime.securesms.mms.GlideRequests;
-import org.thoughtcrime.securesms.util.StableIdGenerator;
+import org.thoughtcrime.securesms.util.adapter.StableIdGenerator;
 
 import java.util.ArrayList;
 import java.util.List;

src/org/thoughtcrime/securesms/mediasend/MediaPickerItemAdapter.java

@@ -14,7 +14,7 @@ import com.bumptech.glide.load.resource.drawable.DrawableTransitionOptions;
 import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.mms.GlideRequests;
 import org.thoughtcrime.securesms.util.MediaUtil;
-import org.thoughtcrime.securesms.util.StableIdGenerator;
+import org.thoughtcrime.securesms.util.adapter.StableIdGenerator;
 
 import java.util.ArrayList;
 import java.util.Collection;

src/org/thoughtcrime/securesms/stickers/StickerManagementAdapter.java

@@ -1,8 +1,10 @@
 package org.thoughtcrime.securesms.stickers;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
 import androidx.recyclerview.widget.RecyclerView;
+
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -16,16 +18,13 @@ import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.database.model.StickerPackRecord;
 import org.thoughtcrime.securesms.mms.DecryptableStreamUriLoader.DecryptableUri;
 import org.thoughtcrime.securesms.mms.GlideRequests;
-import org.thoughtcrime.securesms.util.StableIdGenerator;
+import org.thoughtcrime.securesms.util.adapter.SectionedRecyclerViewAdapter;
+import org.thoughtcrime.securesms.util.adapter.StableIdGenerator;
 
 import java.util.ArrayList;
 import java.util.List;
 
-final class StickerManagementAdapter extends RecyclerView.Adapter {
+final class StickerManagementAdapter extends SectionedRecyclerViewAdapter<String, StickerManagementAdapter.StickerSection> {
-
-  private static final int TYPE_HEADER = 1;
-  private static final int TYPE_EMPTY  = 2;
-  private static final int TYPE_PACK   = 3;
 
   private static final String TAG_YOUR_STICKERS    = "YourStickers";
   private static final String TAG_MESSAGE_STICKERS = "MessageStickers";
@@ -33,15 +32,14 @@ final class StickerManagementAdapter extends RecyclerView.Adapter {
 
   private final GlideRequests  glideRequests;
   private final EventListener  eventListener;
-  private final StableIdGenerator<String> stableIdGenerator;
 
-  private final List<Section> sections = new ArrayList<Section>(3) {{
+  private final List<StickerSection> sections = new ArrayList<StickerSection>(3) {{
-    Section yourStickers    = new Section(TAG_YOUR_STICKERS,
+    StickerSection yourStickers    = new StickerSection(TAG_YOUR_STICKERS,
                                                         R.string.StickerManagementAdapter_installed_stickers,
                                                         R.string.StickerManagementAdapter_no_stickers_installed,
                                                         new ArrayList<>(),
                                                         0);
-    Section messageStickers = new Section(TAG_MESSAGE_STICKERS,
+    StickerSection messageStickers = new StickerSection(TAG_MESSAGE_STICKERS,
                                                         R.string.StickerManagementAdapter_stickers_you_received,
                                                         R.string.StickerManagementAdapter_stickers_from_incoming_messages_will_appear_here,
                                                         new ArrayList<>(),
@@ -54,54 +52,31 @@ final class StickerManagementAdapter extends RecyclerView.Adapter {
   StickerManagementAdapter(@NonNull GlideRequests glideRequests, @NonNull EventListener eventListener) {
     this.glideRequests = glideRequests;
     this.eventListener = eventListener;
-    this.stableIdGenerator = new StableIdGenerator<>();
-
-    setHasStableIds(true);
   }
 
   @Override
-  public long getItemId(int position) {
+  protected @NonNull List<StickerSection> getSections() {
-    for (Section section : sections) {
+    return sections;
-      if (section.handles(position)) {
-        return section.getItemId(stableIdGenerator, position);
-      }
-    }
-    throw new NoSectionException();
   }
 
   @Override
-  public int getItemViewType(int position) {
+  protected @NonNull RecyclerView.ViewHolder createHeaderViewHolder(@NonNull ViewGroup parent) {
-    for (Section section : sections) {
+    return new HeaderViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.sticker_management_header_item, parent, false));
-      if (section.handles(position)) {
-        return section.getViewType(position);
-      }
-    }
-    throw new NoSectionException();
   }
 
   @Override
-  public @NonNull RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
+  protected @NonNull RecyclerView.ViewHolder createContentViewHolder(@NonNull ViewGroup parent) {
-    switch (viewType) {
+    return new StickerViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.sticker_management_sticker_item, parent, false));
-      case TYPE_HEADER:
+  }
-        return new HeaderViewHolder(LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.sticker_management_header_item, viewGroup, false));
+
-      case TYPE_EMPTY:
+  @Override
+  protected @NonNull RecyclerView.ViewHolder createEmptyViewHolder(@NonNull ViewGroup viewGroup) {
     return new EmptyViewHolder(LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.sticker_management_empty_item, viewGroup, false));
-      case TYPE_PACK:
-        return new StickerViewHolder(LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.sticker_management_sticker_item, viewGroup, false));
-      default:
-        throw new AssertionError("Unexpected viewType! " + viewType);
-    }
   }
 
   @Override
-  public void onBindViewHolder(@NonNull RecyclerView.ViewHolder viewHolder, int position) {
+  public void bindViewHolder(@NonNull StickerSection section, @NonNull RecyclerView.ViewHolder viewHolder, int position) {
-    for (Section section : sections) {
-      if (section.handles(position)) {
     section.bindViewHolder(viewHolder, position, glideRequests, eventListener);
-        return;
-      }
-    }
-    throw new NoSectionException();
   }
 
   @Override
@@ -111,26 +86,21 @@ final class StickerManagementAdapter extends RecyclerView.Adapter {
     }
   }
 
-  @Override
-  public int getItemCount() {
-    return Stream.of(sections).reduce(0, (sum, section) -> sum + section.size());
-  }
-
   void setPackLists(@NonNull List<StickerPackRecord> installedPacks,
                     @NonNull List<StickerPackRecord> availablePacks,
                     @NonNull List<StickerPackRecord> blessedPacks)
   {
-    Section yourStickers    = new Section(TAG_YOUR_STICKERS,
+    StickerSection yourStickers    = new StickerSection(TAG_YOUR_STICKERS,
                                                         R.string.StickerManagementAdapter_installed_stickers,
                                                         R.string.StickerManagementAdapter_no_stickers_installed,
                                                         installedPacks,
                                                         0);
-    Section blessedStickers = new Section(TAG_BLESSED_STICKERS,
+    StickerSection blessedStickers = new StickerSection(TAG_BLESSED_STICKERS,
                                                         R.string.StickerManagementAdapter_signal_artist_series,
                                                         0,
                                                         blessedPacks,
                                                         yourStickers.size());
-    Section messageStickers = new Section(TAG_MESSAGE_STICKERS,
+    StickerSection messageStickers = new StickerSection(TAG_MESSAGE_STICKERS,
                                                         R.string.StickerManagementAdapter_stickers_you_received,
                                                         R.string.StickerManagementAdapter_stickers_from_incoming_messages_will_appear_here,
                                                         availablePacks,
@@ -148,7 +118,8 @@ final class StickerManagementAdapter extends RecyclerView.Adapter {
     notifyDataSetChanged();
   }
 
-  private static class Section {
+  public static class StickerSection extends SectionedRecyclerViewAdapter.Section<String> {
+
     private static final String STABLE_ID_HEADER = "header";
     private static final String STABLE_ID_TEXT   = "text";
 
@@ -156,35 +127,34 @@ final class StickerManagementAdapter extends RecyclerView.Adapter {
     private final int                     titleResId;
     private final int                     emptyResId;
     private final List<StickerPackRecord> records;
-    private final int                     offset;
 
-    Section(@NonNull String tag,
+    StickerSection(@NonNull String tag,
                    @StringRes int titleResId,
                    @StringRes int emptyResId,
                    @NonNull List<StickerPackRecord> records,
                    int offset)
     {
+      super(offset);
+
       this.tag        = tag;
       this.titleResId = titleResId;
       this.emptyResId = emptyResId;
       this.records    = records;
-      this.offset     = offset;
     }
 
-    int getViewType(int globalPosition) {
+    @Override
-      int localPosition = globalPosition - offset;
+    public boolean hasEmptyState() {
-
+      return true;
-      if (localPosition == 0) {
-        return TYPE_HEADER;
-      } else if (records.isEmpty()) {
-        return TYPE_EMPTY;
-      } else {
-        return TYPE_PACK;
-      }
     }
 
-    long getItemId(@NonNull StableIdGenerator<String> idGenerator, int globalPosition) {
+    @Override
-      int localPosition = globalPosition - offset;
+    public int getContentSize() {
+      return records.size();
+    }
+
+    @Override
+    public long getItemId(@NonNull StableIdGenerator<String> idGenerator, int globalPosition) {
+      int localPosition = getLocalPosition(globalPosition);
 
       if (localPosition == 0) {
         return idGenerator.getId(tag + "_" + STABLE_ID_HEADER);
@@ -200,7 +170,7 @@ final class StickerManagementAdapter extends RecyclerView.Adapter {
                         @NonNull GlideRequests glideRequests,
                         @NonNull EventListener eventListener)
     {
-      int localPosition = globalPosition - offset;
+      int localPosition = getLocalPosition(globalPosition);
 
       if (localPosition == 0) {
         ((HeaderViewHolder) viewHolder).bind(titleResId);
@@ -210,15 +180,6 @@ final class StickerManagementAdapter extends RecyclerView.Adapter {
         ((StickerViewHolder) viewHolder).bind(glideRequests, eventListener, records.get(localPosition - 1), localPosition == records.size());
       }
     }
-
-    boolean handles(int globalPosition) {
-      int localPosition = globalPosition - offset;
-      return localPosition >= 0 && localPosition < size();
-    }
-
-    int size() {
-      return records.isEmpty() ? 2 : records.size() + 1;
-    }
   }
 
   static class StickerViewHolder extends RecyclerView.ViewHolder {

src/org/thoughtcrime/securesms/util/adapter/SectionedRecyclerViewAdapter.java

@@ -0,0 +1,142 @@
+package org.thoughtcrime.securesms.util.adapter;
+
+import android.view.ViewGroup;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.recyclerview.widget.RecyclerView;
+
+import com.annimon.stream.Stream;
+
+import java.util.List;
+
+/**
+ * A {@link RecyclerView.Adapter} subclass that makes it easier to have sectioned content, where
+ * you have header rows and content rows.
+ *
+ * @param <IdType> The type you'll use to generate stable IDs.
+ * @param <SectionImpl> The subclass of {@link Section} you're using.
+ */
+public abstract class SectionedRecyclerViewAdapter<IdType, SectionImpl extends SectionedRecyclerViewAdapter.Section<IdType>> extends RecyclerView.Adapter {
+
+  private static final int TYPE_HEADER  = 1;
+  private static final int TYPE_CONTENT = 2;
+  private static final int TYPE_EMPTY   = 3;
+
+  private final StableIdGenerator<IdType> stableIdGenerator;
+
+  public SectionedRecyclerViewAdapter() {
+    this.stableIdGenerator = new StableIdGenerator<>();
+    setHasStableIds(true);
+  }
+
+  protected @NonNull abstract List<SectionImpl> getSections();
+  protected @NonNull abstract RecyclerView.ViewHolder createHeaderViewHolder(@NonNull ViewGroup parent);
+  protected @NonNull abstract RecyclerView.ViewHolder createContentViewHolder(@NonNull ViewGroup parent);
+  protected @Nullable abstract RecyclerView.ViewHolder createEmptyViewHolder(@NonNull ViewGroup viewGroup);
+  protected abstract void bindViewHolder(@NonNull SectionImpl section, @NonNull RecyclerView.ViewHolder holder, int position);
+
+  @Override
+  public @NonNull RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
+    switch (viewType) {
+      case TYPE_HEADER:
+        return createHeaderViewHolder(viewGroup);
+      case TYPE_CONTENT:
+        return createContentViewHolder(viewGroup);
+      case TYPE_EMPTY:
+        RecyclerView.ViewHolder holder = createEmptyViewHolder(viewGroup);
+        if (holder == null) {
+          throw new IllegalStateException("Expected an empty view holder, but got none!");
+        }
+        return holder;
+      default:
+        throw new AssertionError("Unexpected viewType! " + viewType);
+    }
+  }
+
+  @Override
+  public long getItemId(int position) {
+    for (SectionImpl section: getSections()) {
+      if (section.handles(position)) {
+        return section.getItemId(stableIdGenerator, position);
+      }
+    }
+    throw new NoSectionException();
+  }
+
+  @Override
+  public int getItemViewType(int position) {
+    for (SectionImpl section : getSections()) {
+      if (section.handles(position)) {
+        return section.getViewType(position);
+      }
+    }
+    throw new NoSectionException();
+  }
+
+  @Override
+  public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
+    for (SectionImpl section : getSections()) {
+      if (section.handles(position)) {
+        bindViewHolder(section, holder, position);
+        return;
+      }
+    }
+    throw new NoSectionException();
+  }
+
+  @Override
+  public int getItemCount() {
+    return Stream.of(getSections()).reduce(0, (sum, section) -> sum + section.size());
+  }
+
+  /**
+   * Represents a section of content in the adapter. Has a header and content.
+   * @param <E> The type you'll use to generate stable IDs.
+   */
+  public static abstract class Section<E> {
+
+    private final int offset;
+
+    public Section(int offset) {
+      this.offset = offset;
+    }
+
+    public abstract boolean hasEmptyState();
+    public abstract int getContentSize();
+    public abstract long getItemId(@NonNull StableIdGenerator<E> idGenerator, int globalPosition);
+
+    protected int getLocalPosition(int globalPosition) {
+      return globalPosition - offset;
+    }
+
+    public int getViewType(int globalPosition) {
+      int localPosition = globalPosition - offset;
+
+      if (localPosition == 0) {
+        return TYPE_HEADER;
+      } else if (getContentSize() == 0) {
+        return TYPE_EMPTY;
+      } else {
+        return TYPE_CONTENT;
+      }
+    }
+
+    public boolean handles(int globalPosition) {
+      int localPosition = globalPosition - offset;
+      return localPosition >= 0 && localPosition < size();
+    }
+
+    public int size() {
+      if (getContentSize() == 0 && hasEmptyState()) {
+        return 2;
+      } else if (getContentSize() == 0) {
+        return 0;
+      } else {
+        return getContentSize() + 1;
+      }
+    }
+  }
+
+  private static class NoSectionException extends IllegalStateException {}
+}

src/org/thoughtcrime/securesms/util/adapter/StableIdGenerator.java

@@ -1,4 +1,4 @@
-package org.thoughtcrime.securesms.util;
+package org.thoughtcrime.securesms.util.adapter;
 
 import androidx.annotation.MainThread;
 import androidx.annotation.NonNull;