Use listener notification batching in CastPlayer

PiperOrigin-RevId: 251399230

extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastPlayer.java

@@ -45,8 +45,11 @@ import com.google.android.gms.cast.framework.media.RemoteMediaClient;
 import com.google.android.gms.cast.framework.media.RemoteMediaClient.MediaChannelResult;
 import com.google.android.gms.common.api.PendingResult;
 import com.google.android.gms.common.api.ResultCallback;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
-import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.concurrent.CopyOnWriteArrayList;
 
 /**
  * {@link Player} implementation that communicates with a Cast receiver app.
@@ -86,8 +89,10 @@ public final class CastPlayer extends BasePlayer {
   private final StatusListener statusListener;
   private final SeekResultCallback seekResultCallback;
 
-  // Listeners.
+  // Listeners and notification.
-  private final CopyOnWriteArraySet<EventListener> listeners;
+  private final CopyOnWriteArrayList<ListenerHolder> listeners;
+  private final ArrayList<ListenerNotificationTask> notificationsBatch;
+  private final ArrayDeque<ListenerNotificationTask> ongoingNotificationsTasks;
   private SessionAvailabilityListener sessionAvailabilityListener;
 
   // Internal state.
@@ -113,7 +118,9 @@ public final class CastPlayer extends BasePlayer {
     period = new Timeline.Period();
     statusListener = new StatusListener();
     seekResultCallback = new SeekResultCallback();
-    listeners = new CopyOnWriteArraySet<>();
+    listeners = new CopyOnWriteArrayList<>();
+    notificationsBatch = new ArrayList<>();
+    ongoingNotificationsTasks = new ArrayDeque<>();
 
     SessionManager sessionManager = castContext.getSessionManager();
     sessionManager.addSessionManagerListener(statusListener, CastSession.class);
@@ -296,12 +303,17 @@ public final class CastPlayer extends BasePlayer {
 
   @Override
   public void addListener(EventListener listener) {
-    listeners.add(listener);
+    listeners.addIfAbsent(new ListenerHolder(listener));
   }
 
   @Override
   public void removeListener(EventListener listener) {
-    listeners.remove(listener);
+    for (ListenerHolder listenerHolder : listeners) {
+      if (listenerHolder.listener.equals(listener)) {
+        listenerHolder.release();
+        listeners.remove(listenerHolder);
+      }
+    }
   }
 
   @Override
@@ -348,14 +360,13 @@ public final class CastPlayer extends BasePlayer {
       pendingSeekCount++;
       pendingSeekWindowIndex = windowIndex;
       pendingSeekPositionMs = positionMs;
-      for (EventListener listener : listeners) {
+      notificationsBatch.add(
-        listener.onPositionDiscontinuity(Player.DISCONTINUITY_REASON_SEEK);
+          new ListenerNotificationTask(
-      }
+              listener -> listener.onPositionDiscontinuity(DISCONTINUITY_REASON_SEEK)));
     } else if (pendingSeekCount == 0) {
-      for (EventListener listener : listeners) {
+      notificationsBatch.add(new ListenerNotificationTask(EventListener::onSeekProcessed));
-        listener.onSeekProcessed();
-      }
     }
+    flushNotifications();
   }
 
   @Override
@@ -531,30 +542,31 @@ public final class CastPlayer extends BasePlayer {
         || this.playWhenReady != playWhenReady) {
       this.playbackState = playbackState;
       this.playWhenReady = playWhenReady;
-      for (EventListener listener : listeners) {
+      notificationsBatch.add(
-        listener.onPlayerStateChanged(this.playWhenReady, this.playbackState);
+          new ListenerNotificationTask(
-      }
+              listener -> listener.onPlayerStateChanged(this.playWhenReady, this.playbackState)));
     }
     @RepeatMode int repeatMode = fetchRepeatMode(remoteMediaClient);
     if (this.repeatMode != repeatMode) {
       this.repeatMode = repeatMode;
-      for (EventListener listener : listeners) {
+      notificationsBatch.add(
-        listener.onRepeatModeChanged(repeatMode);
+          new ListenerNotificationTask(listener -> listener.onRepeatModeChanged(this.repeatMode)));
-      }
     }
     int currentWindowIndex = fetchCurrentWindowIndex(getMediaStatus());
     if (this.currentWindowIndex != currentWindowIndex && pendingSeekCount == 0) {
       this.currentWindowIndex = currentWindowIndex;
-      for (EventListener listener : listeners) {
+      notificationsBatch.add(
-        listener.onPositionDiscontinuity(DISCONTINUITY_REASON_PERIOD_TRANSITION);
+          new ListenerNotificationTask(
-      }
+              listener ->
+                  listener.onPositionDiscontinuity(DISCONTINUITY_REASON_PERIOD_TRANSITION)));
     }
     if (updateTracksAndSelections()) {
-      for (EventListener listener : listeners) {
+      notificationsBatch.add(
-        listener.onTracksChanged(currentTrackGroups, currentTrackSelection);
+          new ListenerNotificationTask(
-      }
+              listener -> listener.onTracksChanged(currentTrackGroups, currentTrackSelection)));
     }
     maybeUpdateTimelineAndNotify();
+    flushNotifications();
   }
 
   private void maybeUpdateTimelineAndNotify() {
@@ -562,9 +574,10 @@ public final class CastPlayer extends BasePlayer {
       @Player.TimelineChangeReason int reason = waitingForInitialTimeline
           ? Player.TIMELINE_CHANGE_REASON_PREPARED : Player.TIMELINE_CHANGE_REASON_DYNAMIC;
       waitingForInitialTimeline = false;
-      for (EventListener listener : listeners) {
+      notificationsBatch.add(
-        listener.onTimelineChanged(currentTimeline, null, reason);
+          new ListenerNotificationTask(
-      }
+              listener ->
+                  listener.onTimelineChanged(currentTimeline, /* manifest= */ null, reason)));
     }
   }
 
@@ -827,7 +840,23 @@ public final class CastPlayer extends BasePlayer {
 
   }
 
-  // Result callbacks hooks.
+  // Internal methods.
+
+  private void flushNotifications() {
+    boolean recursiveNotification = !ongoingNotificationsTasks.isEmpty();
+    ongoingNotificationsTasks.addAll(notificationsBatch);
+    notificationsBatch.clear();
+    if (recursiveNotification) {
+      // This will be handled once the current notification task is finished.
+      return;
+    }
+    while (!ongoingNotificationsTasks.isEmpty()) {
+      ongoingNotificationsTasks.peekFirst().execute();
+      ongoingNotificationsTasks.removeFirst();
+    }
+  }
+
+  // Internal classes.
 
   private final class SeekResultCallback implements ResultCallback<MediaChannelResult> {
 
@@ -841,11 +870,27 @@ public final class CastPlayer extends BasePlayer {
       if (--pendingSeekCount == 0) {
         pendingSeekWindowIndex = C.INDEX_UNSET;
         pendingSeekPositionMs = C.TIME_UNSET;
-        for (EventListener listener : listeners) {
+        notificationsBatch.add(new ListenerNotificationTask(EventListener::onSeekProcessed));
-          listener.onSeekProcessed();
+        flushNotifications();
       }
     }
   }
+
+  private final class ListenerNotificationTask {
+
+    private final Iterator<ListenerHolder> listenersSnapshot;
+    private final ListenerInvocation listenerInvocation;
+
+    private ListenerNotificationTask(ListenerInvocation listenerInvocation) {
+      this.listenersSnapshot = listeners.iterator();
+      this.listenerInvocation = listenerInvocation;
+    }
+
+    public void execute() {
+      while (listenersSnapshot.hasNext()) {
+        listenersSnapshot.next().invoke(listenerInvocation);
+      }
+    }
   }
 
 }