Move EventListener registration down from Player

The deprecated `Player.addListener(EventListener)`
is moved out of Player into its subclasses
(CastPlayer and ExoPlayer).

This is unlikely to break users because:
 - the method has been deprecated in the last major version
 - the method is still present in the major implementations

If an users is affected, they can either:
 - use ExoPlayer instead of Player
 - (recommended) switch to Player.Listener.

Additionally update the threading guarantees that did not
reflect the current implementation.

PiperOrigin-RevId: 397272144

RELEASENOTES.md

@@ -24,6 +24,8 @@
         the start or after the end of the media are now handled as seeks to the
         start and end respectively
         ([#8906](https://github.com/google/ExoPlayer/issues/8906)).
+    *   Move `Player.addListener(EventListener)` and
+        `Player.removeListener(EventListener)` out of `Player` into subclasses.
 *   Extractors:
     *   Support TS packets without PTS flag
         ([#9294](https://github.com/google/ExoPlayer/issues/9294)).
@@ -92,9 +94,8 @@
         deprecated since 2.11.0.
     *   Remove `DownloadService.onDownloadChanged` and
         `DownloadService.onDownloadRemoved`. Instead, use
-        `DownloadManager.addListener` to register a listener directly to
+        `DownloadManager.addListener` to register a listener directly to the
-        the `DownloadManager` returned through
+        `DownloadManager` returned through `DownloadService.getDownloadManager`.
-        `DownloadService.getDownloadManager`.
 *   Cast extension:
     *   Implement `CastPlayer.setPlaybackParameters(PlaybackParameters)` to
         support setting the playback speed

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

@@ -276,7 +276,17 @@ public final class CastPlayer extends BasePlayer {
     addListener(eventListener);
   }
 
-  @Override
+  /**
+   * Registers a listener to receive events from the player.
+   *
+   * <p>The listener's methods will be called on the thread associated with {@link
+   * #getApplicationLooper()}.
+   *
+   * @param listener The listener to register.
+   * @deprecated Use {@link #addListener(Listener)} and {@link #removeListener(Listener)} instead.
+   */
+  @Deprecated
+  @SuppressWarnings("deprecation")
   public void addListener(EventListener listener) {
     listeners.add(listener);
   }
@@ -287,7 +297,15 @@ public final class CastPlayer extends BasePlayer {
     removeListener(eventListener);
   }
 
-  @Override
+  /**
+   * Unregister a listener registered through {@link #addListener(EventListener)}. The listener will
+   * no longer receive events from the player.
+   *
+   * @param listener The listener to unregister.
+   * @deprecated Use {@link #addListener(Listener)} and {@link #removeListener(Listener)} instead.
+   */
+  @Deprecated
+  @SuppressWarnings("deprecation")
   public void removeListener(EventListener listener) {
     listeners.remove(listener);
   }

library/common/src/main/java/com/google/android/exoplayer2/ForwardingPlayer.java

@@ -43,28 +43,16 @@ public class ForwardingPlayer implements Player {
     this.player = player;
   }
 
-  @Override
+  @Deprecated
   public Looper getApplicationLooper() {
     return player.getApplicationLooper();
   }
 
   @Deprecated
-  @Override
-  public void addListener(EventListener listener) {
-    player.addListener(new ForwardingEventListener(this, listener));
-  }
-
-  @Override
   public void addListener(Listener listener) {
     player.addListener(new ForwardingListener(this, listener));
   }
 
-  @Deprecated
-  @Override
-  public void removeListener(EventListener listener) {
-    player.removeListener(new ForwardingEventListener(this, listener));
-  }
-
   @Override
   public void removeListener(Listener listener) {
     player.removeListener(new ForwardingListener(this, listener));

library/common/src/main/java/com/google/android/exoplayer2/Player.java

@@ -1434,40 +1434,16 @@ public interface Player {
    */
   Looper getApplicationLooper();
 
-  /**
-   * Registers a listener to receive events from the player.
-   *
-   * <p>The listener's methods will be called on the thread that was used to construct the player.
-   * However, if the thread used to construct the player does not have a {@link Looper}, then the
-   * listener will be called on the main thread.
-   *
-   * @param listener The listener to register.
-   * @deprecated Use {@link #addListener(Listener)} and {@link #removeListener(Listener)} instead.
-   */
-  @Deprecated
-  void addListener(EventListener listener);
-
   /**
    * Registers a listener to receive all events from the player.
    *
-   * <p>The listener's methods will be called on the thread that was used to construct the player.
+   * <p>The listener's methods will be called on the thread associated with {@link
-   * However, if the thread used to construct the player does not have a {@link Looper}, then the
+   * #getApplicationLooper()}.
-   * listener will be called on the main thread.
    *
    * @param listener The listener to register.
    */
   void addListener(Listener listener);
 
-  /**
-   * Unregister a listener registered through {@link #addListener(EventListener)}. The listener will
-   * no longer receive events from the player.
-   *
-   * @param listener The listener to unregister.
-   * @deprecated Use {@link #addListener(Listener)} and {@link #removeListener(Listener)} instead.
-   */
-  @Deprecated
-  void removeListener(EventListener listener);
-
   /**
    * Unregister a listener registered through {@link #addListener(Listener)}. The listener will no
    * longer receive events.

library/common/src/test/java/com/google/android/exoplayer2/ForwardingPlayerTest.java

@@ -61,22 +61,6 @@ public class ForwardingPlayerTest {
     assertThat(player.listeners).hasSize(2);
   }
 
-  @Test
-  @SuppressWarnings("deprecation") // Testing backwards compatibility with deprecated method.
-  public void addEventListener_addsForwardingListener() {
-    FakePlayer player = new FakePlayer(ApplicationProvider.getApplicationContext());
-    Player.EventListener listener1 = mock(Player.EventListener.class);
-    Player.EventListener listener2 = mock(Player.EventListener.class);
-
-    ForwardingPlayer forwardingPlayer = new ForwardingPlayer(player);
-    forwardingPlayer.addListener(listener1);
-    // Add listener1 again.
-    forwardingPlayer.addListener(listener1);
-    forwardingPlayer.addListener(listener2);
-
-    assertThat(player.eventListeners).hasSize(2);
-  }
-
   @Test
   public void removeListener_removesForwardingListener() {
     FakePlayer player = new FakePlayer(ApplicationProvider.getApplicationContext());
@@ -95,25 +79,6 @@ public class ForwardingPlayerTest {
     assertThat(player.listeners).isEmpty();
   }
 
-  @Test
-  @SuppressWarnings("deprecation") // Testing backwards compatibility with deprecated method.
-  public void removeEventListener_removesForwardingListener() {
-    FakePlayer player = new FakePlayer(ApplicationProvider.getApplicationContext());
-    Player.EventListener listener1 = mock(Player.EventListener.class);
-    Player.EventListener listener2 = mock(Player.EventListener.class);
-    ForwardingPlayer forwardingPlayer = new ForwardingPlayer(player);
-    forwardingPlayer.addListener(listener1);
-    forwardingPlayer.addListener(listener2);
-
-    forwardingPlayer.removeListener(listener1);
-    assertThat(player.eventListeners).hasSize(1);
-    // Remove same listener again.
-    forwardingPlayer.removeListener(listener1);
-    assertThat(player.eventListeners).hasSize(1);
-    forwardingPlayer.removeListener(listener2);
-    assertThat(player.eventListeners).isEmpty();
-  }
-
   @Test
   public void onEvents_passesForwardingPlayerAsArgument() {
     FakePlayer player = new FakePlayer(ApplicationProvider.getApplicationContext());
@@ -217,32 +182,17 @@ public class ForwardingPlayerTest {
 
   private static class FakePlayer extends StubExoPlayer {
 
-    @SuppressWarnings("deprecation") // Use of deprecated type for backwards compatibility.
-    private final Set<EventListener> eventListeners = new HashSet<>();
-
     private final Set<Listener> listeners = new HashSet<>();
 
     public FakePlayer(Context context) {
       super(context);
     }
 
-    @Override
-    @SuppressWarnings("deprecation") // Implementing deprecated method.
-    public void addListener(EventListener listener) {
-      eventListeners.add(listener);
-    }
-
     @Override
     public void addListener(Listener listener) {
       listeners.add(listener);
     }
 
-    @Override
-    @SuppressWarnings("deprecation") // Implementing deprecated method.
-    public void removeListener(EventListener listener) {
-      eventListeners.remove(listener);
-    }
-
     @Override
     public void removeListener(Listener listener) {
       listeners.remove(listener);

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayer.java

@@ -873,6 +873,30 @@ public interface ExoPlayer extends Player {
   @Deprecated
   DeviceComponent getDeviceComponent();
 
+  /**
+   * Registers a listener to receive events from the player.
+   *
+   * <p>The listener's methods will be called on the thread associated with {@link
+   * #getApplicationLooper()}.
+   *
+   * @param listener The listener to register.
+   * @deprecated Use {@link #addListener(Listener)} and {@link #removeListener(Listener)} instead.
+   */
+  @Deprecated
+  @SuppressWarnings("deprecation")
+  void addListener(EventListener listener);
+
+  /**
+   * Unregister a listener registered through {@link #addListener(EventListener)}. The listener will
+   * no longer receive events from the player.
+   *
+   * @param listener The listener to unregister.
+   * @deprecated Use {@link #addListener(Listener)} and {@link #removeListener(Listener)} instead.
+   */
+  @Deprecated
+  @SuppressWarnings("deprecation")
+  void removeListener(EventListener listener);
+
   /**
    * Adds a listener to receive audio offload events.
    *

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java

@@ -289,24 +289,22 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public void addListener(Listener listener) {
-    EventListener eventListener = listener;
+    addEventListener(listener);
-    addListener(eventListener);
-  }
-
-  @Override
-  public void addListener(Player.EventListener listener) {
-    listeners.add(listener);
   }
 
   @Override
   public void removeListener(Listener listener) {
-    EventListener eventListener = listener;
+    removeEventListener(listener);
-    removeListener(eventListener);
   }
 
-  @Override
+  @SuppressWarnings("deprecation") // Register deprecated EventListener.
-  public void removeListener(Player.EventListener listener) {
+  public void addEventListener(Player.EventListener eventListener) {
-    listeners.remove(listener);
+    listeners.add(eventListener);
+  }
+
+  @SuppressWarnings("deprecation") // Deregister deprecated EventListener.
+  public void removeEventListener(Player.EventListener eventListener) {
+    listeners.remove(eventListener);
   }
 
   public void addAudioOffloadListener(AudioOffloadListener listener) {

library/core/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java

@@ -558,7 +558,7 @@ public class SimpleExoPlayer extends BasePlayer
               builder.looper,
               /* wrappingPlayer= */ this,
               additionalPermanentAvailableCommands);
-      player.addListener(componentListener);
+      player.addEventListener(componentListener);
       player.addAudioOffloadListener(componentListener);
       if (builder.foregroundModeTimeoutMs > 0) {
         player.experimentalSetForegroundModeTimeoutMs(builder.foregroundModeTimeoutMs);
@@ -1082,7 +1082,7 @@ public class SimpleExoPlayer extends BasePlayer
   public void addListener(Player.EventListener listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
     Assertions.checkNotNull(listener);
-    player.addListener(listener);
+    player.addEventListener(listener);
   }
 
   @Override
@@ -1097,7 +1097,7 @@ public class SimpleExoPlayer extends BasePlayer
   @Override
   public void removeListener(Player.EventListener listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
-    player.removeListener(listener);
+    player.removeEventListener(listener);
   }
 
   @Override