Events with Litho

EventHandler.java

final EventDispatcher likeEventDispatcher = new EventDispatcher() {
  @Override
  public Object dispatchOnEvent(EventHandler eventHandler, Object eventState) {
    // Do stuff here
    return null;
  }
};

HasEventDispatcher hasEventDispatcher = new HasEventDispatcher() {
  @Override
  public EventDispatcher getEventDispatcher() {
    return likeEventDispatcher;
  }
};

EventHandler<LikeChangeEvent> likeChangeEventEventHandler = new EventHandler<>(hasEventDispatcher, 1, null);

GifItemViewSpec.java

@LayoutSpec(events = { LikeChangeEvent.class, GifSelectEvent.class })
public class GifItemViewSpec {

  @OnCreateInitialState
  static void createInitialState(ComponentContext c, StateValue<Boolean> isLiked, @Prop boolean initLiked) {
    isLiked.set(initLiked);
  }

  @OnCreateLayout
  static ComponentLayout onCreateLayout(ComponentContext context, @Prop GifItem gif,
                      @Prop RequestManager glide, @State boolean isLiked) {
    return Column.create(context)
        .child(GifImageView.create(context)
              .gif(gif)
              .glide(glide)
              .withLayout()
              .alignSelf(YogaAlign.CENTER)
              .build())
        .child(Image.create(context)
            .drawableRes(isLiked ? R.drawable.ic_favorite_accent_24dp :R.drawable.ic_favorite_border_accent_24dp)
            .withLayout()
            .clickHandler(GifItemView.onLikeButtonClicked(context))
            .positionType(YogaPositionType.ABSOLUTE)
            .widthDip(40)
            .heightDip(40)
            .paddingDip(YogaEdge.ALL, 8)
            .alignSelf(YogaAlign.FLEX_END)
            .build())
        .clickHandler(GifItemView.onViewClicked(context))
        .build();
  }

  @OnUpdateState
  static void updateLikeButton(StateValue<Boolean> isLiked, @Param boolean updatedValue) {
    isLiked.set(updatedValue);
  }

  @OnEvent(ClickEvent.class)
  static void onLikeButtonClicked(ComponentContext c, @State boolean isLiked, @Prop GifItem gif) {
    GifItemView.updateLikeButtonAsync(c, !isLiked);
    GifItemView.dispatchLikeChangeEvent(GifItemView.getLikeChangeEventHandler(c), gif.getId(), !isLiked);
  }

  @OnEvent(ClickEvent.class)
  static void onViewClicked(ComponentContext c, @Prop GifItem gif) {
    GifItemView.dispatchGifSelectEvent(GifItemView.getGifSelectEventHandler(c), gif);
  }
}

GifSelectEvent.java

@Event
public class GifSelectEvent {
	public GifItem gif;
}

LikeChangeEvent.java

@Event
public class LikeChangeEvent {
  public String gifId;
  public boolean isLiked;
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

  private Component homeComponent;
  private LithoView root;
  private boolean isFullScreen;

  private static final int LIKE_CHANGE_EVENT_ID = 11;
  private static final int GIF_SELECT_EVENT_ID = 12;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    
    ... some code here

    final LikeStore likeStore = new PreferenceLikeStore(this);

    final EventHandler likeChangeHandler = new EventHandler(new HasEventDispatcher() {
      @Override
      public EventDispatcher getEventDispatcher() {
        return new EventDispatcher() {
          @Override
          public Object dispatchOnEvent(EventHandler eventHandler, Object eventState) {
            LikeChangeEvent event = (LikeChangeEvent) eventState;
            likeStore.setLiked(event.gifId, event.isLiked);
            return null;
          }
        };
      }
    }, LIKE_CHANGE_EVENT_ID, null);

    final EventHandler gifSelectHandler = new EventHandler(new HasEventDispatcher() {
      @Override
      public EventDispatcher getEventDispatcher() {
        return new EventDispatcher() {
          @Override
          public Object dispatchOnEvent(EventHandler eventHandler, Object eventState) {
            GifSelectEvent event = (GifSelectEvent) eventState;
            showFullScreen(c, glide, event.gif, likeStore, likeChangeHandler);
            return null;
          }
        };
      }
    }, GIF_SELECT_EVENT_ID, null);

    final GifProvider.ResponseListener responseListener = new GifProvider.ResponseListener() {
      @Override
      public void onSuccess(List<GifItem> gifs) {
        updateContent(c, binder, glide, gifs, likeChangeHandler, gifSelectHandler);
      }

      @Override
      public void onFailure(Throwable t) {
        t.printStackTrace();
      }
    };

    ... some code here    
  }

  private void showFullScreen(ComponentContext context, RequestManager glide, GifItem gif,
                final LikeStore likeStore, EventHandler likeChangeHandler) {
    Component fullScreenComponent = FullScreenComponent.create(context)
        .initLiked(likeStore.isLiked(gif.getId()))
        .gif(gif)
        .key(gif.getId())
        .glide(glide)
        .likeChangeEventHandler(likeChangeHandler)
        .build();

    root.setComponent(fullScreenComponent);
    isFullScreen = true;
  }
  
  private void updateContent(ComponentContext c, RecyclerBinder binder, List<GifItem> gifs, EventHandler likeChangeHandler,
                            EventHandler gifSelectHandler) {
    binder.removeRangeAt(0, binder.getItemCount());
    List<ComponentInfo> components = new ArrayList<>();
    for (GifItem gif: gifs) {
      components.add(ComponentInfo.create().component(
          GifItemView.create(c)
              .initLiked(gif.isLiked())
              .gif(gif)
              .key(gif.getId())
              .likeChangeEventHandler(likeChangeHandler)
              .gifSelectEventHandler(gifSelectHandler)
              .build()
        ).build()
      );
    }
    binder.insertRangeAt(0, components);
  }
}