Add methods in TrackSelection to get details about the playback state.

Determine whether a rebuffer occurred and if the playback is paused or resumed.

PiperOrigin-RevId: 342849010

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

@@ -724,6 +724,19 @@ import java.util.concurrent.atomic.AtomicBoolean;
     handleMediaSourceListInfoRefreshed(timeline);
   }
 
+  private void notifyTrackSelectionPlayWhenReadyChanged(boolean playWhenReady) {
+    MediaPeriodHolder periodHolder = queue.getPlayingPeriod();
+    while (periodHolder != null) {
+      TrackSelection[] trackSelections = periodHolder.getTrackSelectorResult().selections.getAll();
+      for (TrackSelection trackSelection : trackSelections) {
+        if (trackSelection != null) {
+          trackSelection.onPlayWhenReadyChanged(playWhenReady);
+        }
+      }
+      periodHolder = periodHolder.getNext();
+    }
+  }
+
   private void setPlayWhenReadyInternal(
       boolean playWhenReady,
       @PlaybackSuppressionReason int playbackSuppressionReason,
@@ -734,6 +747,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
     playbackInfoUpdate.setPlayWhenReadyChangeReason(reason);
     playbackInfo = playbackInfo.copyWithPlayWhenReady(playWhenReady, playbackSuppressionReason);
     isRebuffering = false;
+    notifyTrackSelectionPlayWhenReadyChanged(playWhenReady);
     if (!shouldPlayWhenReady()) {
       stopRenderers();
       updatePlaybackPositions();
@@ -880,6 +894,19 @@ import java.util.concurrent.atomic.AtomicBoolean;
     }
   }
 
+  private void notifyTrackSelectionRebuffer() {
+    MediaPeriodHolder periodHolder = queue.getPlayingPeriod();
+    while (periodHolder != null) {
+      TrackSelection[] trackSelections = periodHolder.getTrackSelectorResult().selections.getAll();
+      for (TrackSelection trackSelection : trackSelections) {
+        if (trackSelection != null) {
+          trackSelection.onRebuffer();
+        }
+      }
+      periodHolder = periodHolder.getNext();
+    }
+  }
+
   private void doSomeWork() throws ExoPlaybackException, IOException {
     long operationStartTimeMs = clock.uptimeMillis();
     updatePeriods();
@@ -964,6 +991,9 @@ import java.util.concurrent.atomic.AtomicBoolean;
         && !(enabledRendererCount == 0 ? isTimelineReady() : renderersAllowPlayback)) {
       isRebuffering = shouldPlayWhenReady();
       setState(Player.STATE_BUFFERING);
+      if (isRebuffering) {
+        notifyTrackSelectionRebuffer();
+      }
       livePlaybackSpeedControl.notifyRebuffer();
       stopRenderers();
     }

library/core/src/main/java/com/google/android/exoplayer2/trackselection/TrackSelection.java

@@ -73,9 +73,7 @@ public interface TrackSelection {
     }
   }
 
-  /**
+  /** Factory for {@link TrackSelection} instances. */
-   * Factory for {@link TrackSelection} instances.
-   */
   interface Factory {
 
     /**
@@ -118,16 +116,12 @@ public interface TrackSelection {
    */
   void disable();
 
-  /**
+  /** Returns the {@link TrackGroup} to which the selected tracks belong. */
-   * Returns the {@link TrackGroup} to which the selected tracks belong.
-   */
   TrackGroup getTrackGroup();
 
   // Static subset of selected tracks.
 
-  /**
+  /** Returns the number of tracks in the selection. */
-   * Returns the number of tracks in the selection.
-   */
   int length();
 
   /**
@@ -168,28 +162,21 @@ public interface TrackSelection {
 
   // Individual selected track.
 
-  /**
+  /** Returns the {@link Format} of the individual selected track. */
-   * Returns the {@link Format} of the individual selected track.
-   */
   Format getSelectedFormat();
 
-  /**
+  /** Returns the index in the track group of the individual selected track. */
-   * Returns the index in the track group of the individual selected track.
-   */
   int getSelectedIndexInTrackGroup();
 
-  /**
+  /** Returns the index of the selected track. */
-   * Returns the index of the selected track.
-   */
   int getSelectedIndex();
 
-  /**
+  /** Returns the reason for the current track selection. */
-   * Returns the reason for the current track selection.
-   */
   int getSelectionReason();
 
   /** Returns optional data associated with the current track selection. */
-  @Nullable Object getSelectionData();
+  @Nullable
+  Object getSelectionData();
 
   // Adaptation.
 
@@ -208,6 +195,22 @@ public interface TrackSelection {
    */
   default void onDiscontinuity() {}
 
+  /**
+   * Called to notify when a rebuffer occurred.
+   *
+   * <p>A rebuffer is defined to be caused by buffer depletion rather than a user action. Hence this
+   * method is not called during initial buffering or when buffering as a result of a seek
+   * operation.
+   */
+  default void onRebuffer() {}
+
+  /**
+   * Called to notify when the playback is paused or resumed.
+   *
+   * @param playWhenReady Whether playback will proceed when ready.
+   */
+  default void onPlayWhenReadyChanged(boolean playWhenReady) {}
+
   /**
    * Updates the selected track for sources that load media in discrete {@link MediaChunk}s.
    *