Add Gif loop end listener

library/build.gradle

@@ -13,6 +13,7 @@ dependencies {
     api project(':third_party:disklrucache')
     api project(':annotation')
     api "com.android.support:support-fragment:${ANDROID_SUPPORT_VERSION}"
+    api "com.android.support:animated-vector-drawable:${ANDROID_SUPPORT_VERSION}"
     compileOnly "com.android.support:appcompat-v7:${ANDROID_SUPPORT_VERSION}"
 
     if (project.plugins.hasPlugin('net.ltgt.errorprone')) {

library/src/main/java/com/bumptech/glide/load/resource/gif/GifDrawable.java

@@ -14,19 +14,22 @@
 import android.graphics.drawable.Drawable;
 import android.support.annotation.NonNull;
 import android.support.annotation.VisibleForTesting;
+import android.support.graphics.drawable.Animatable2Compat;
 import android.view.Gravity;
 import com.bumptech.glide.Glide;
 import com.bumptech.glide.gifdecoder.GifDecoder;
 import com.bumptech.glide.load.Transformation;
 import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
 import com.bumptech.glide.util.Preconditions;
 import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * An animated {@link android.graphics.drawable.Drawable} that plays the frames of an animated GIF.
  */
 public class GifDrawable extends Drawable implements GifFrameLoader.FrameCallback,
-    Animatable {
+    Animatable, Animatable2Compat {
   /**
    * A constant indicating that an animated drawable should loop continuously.
    */
@@ -76,6 +79,11 @@ public class GifDrawable extends Drawable implements GifFrameLoader.FrameCallbac
   private Paint paint;
   private Rect destRect;
 
+  /**
+   * Callbacks to notify loop completion of a gif, where the loop count is explicitly specified.
+   */
+  private List<AnimationCallback> animationCallbacks;
+
   /**
    * Constructor for GifDrawable.
    *
@@ -351,10 +359,19 @@ public void onFrameReady() {
     }
 
     if (maxLoopCount != LOOP_FOREVER && loopCount >= maxLoopCount) {
+      notifyAnimationEndToListeners();
       stop();
     }
   }
 
+  private void notifyAnimationEndToListeners() {
+    if (animationCallbacks != null) {
+      for (int i = 0, size = animationCallbacks.size(); i < size; i++) {
+        animationCallbacks.get(i).onAnimationEnd(this);
+      }
+    }
+  }
+
   @Override
   public ConstantState getConstantState() {
     return state;
@@ -390,6 +407,42 @@ public void setLoopCount(int loopCount) {
     }
   }
 
+  /**
+   * Register callback to listen to GifDrawable animation end event after specific loop count
+   * set by {@link GifDrawable#setLoopCount(int)}.
+   *
+   * Note: This will only be called if the Gif stop because it reaches the loop count. Unregister
+   * this in onLoadCleared to avoid potential memory leak.
+   * @see GifDrawable#unregisterAnimationCallback(AnimationCallback).
+   *
+   * @param animationCallback Animation callback {@link Animatable2Compat.AnimationCallback}.
+   */
+  @Override
+  public void registerAnimationCallback(@NonNull AnimationCallback animationCallback) {
+    if (animationCallback == null) {
+      return;
+    }
+    if (animationCallbacks == null) {
+      animationCallbacks = new ArrayList<>();
+    }
+    animationCallbacks.add(animationCallback);
+  }
+
+  @Override
+  public boolean unregisterAnimationCallback(@NonNull AnimationCallback animationCallback) {
+    if (animationCallbacks == null || animationCallback == null) {
+      return false;
+    }
+    return animationCallbacks.remove(animationCallback);
+  }
+
+  @Override
+  public void clearAnimationCallbacks() {
+    if (animationCallbacks != null) {
+      animationCallbacks.clear();
+    }
+  }
+
   static final class GifState extends ConstantState {
     @VisibleForTesting
     final GifFrameLoader frameLoader;