Add getRenderer method to ExoPlayer.

This allows access to custom renderers, for example to send messages
or to access custom fields and methods.

PiperOrigin-RevId: 424878963

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/ExoPlayer.java

@@ -1135,6 +1135,15 @@ public interface ExoPlayer extends Player {
   @C.TrackType
   int getRendererType(int index);
 
+  /**
+   * Returns the renderer at the given index.
+   *
+   * @param index The index of the renderer.
+   * @return The renderer at this index.
+   */
+  @UnstableApi
+  Renderer getRenderer(int index);
+
   /**
    * Returns the track selector that this player uses, or null if track selection is not supported.
    */

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/ExoPlayerImpl.java

@@ -955,6 +955,10 @@ import java.util.concurrent.CopyOnWriteArraySet;
     return renderers[index].getTrackType();
   }
 
+  public Renderer getRenderer(int index) {
+    return renderers[index];
+  }
+
   public TrackSelector getTrackSelector() {
     return trackSelector;
   }

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/SimpleExoPlayer.java

@@ -358,8 +358,7 @@ public class SimpleExoPlayer extends BasePlayer
 
   private static final String TAG = "SimpleExoPlayer";
 
-  protected final Renderer[] renderers;
+  private final Renderer[] renderers;
-
   private final ConditionVariable constructorFinished;
   private final Context applicationContext;
   private final ExoPlayerImpl player;
@@ -1360,6 +1359,12 @@ public class SimpleExoPlayer extends BasePlayer
     return player.getRendererType(index);
   }
 
+  @Override
+  public Renderer getRenderer(int index) {
+    verifyApplicationThread();
+    return player.getRenderer(index);
+  }
+
   @Override
   public TrackSelector getTrackSelector() {
     verifyApplicationThread();

libraries/test_utils/src/main/java/androidx/media3/test/utils/StubExoPlayer.java

@@ -28,6 +28,7 @@ import androidx.media3.exoplayer.DecoderCounters;
 import androidx.media3.exoplayer.ExoPlaybackException;
 import androidx.media3.exoplayer.ExoPlayer;
 import androidx.media3.exoplayer.PlayerMessage;
+import androidx.media3.exoplayer.Renderer;
 import androidx.media3.exoplayer.SeekParameters;
 import androidx.media3.exoplayer.analytics.AnalyticsCollector;
 import androidx.media3.exoplayer.analytics.AnalyticsListener;
@@ -293,6 +294,11 @@ public class StubExoPlayer extends StubPlayer implements ExoPlayer {
     throw new UnsupportedOperationException();
   }
 
+  @Override
+  public Renderer getRenderer(int index) {
+    throw new UnsupportedOperationException();
+  }
+
   @Override
   @Nullable
   public TrackSelector getTrackSelector() {