MediaSession2: Add SessionCallback#onCurrentMediaItemChanged()

Added callback for session to know the currently playing media item has
changed.

Note that the callback is called in response to the
MediaPlayerBase#PlayerEventCallback#onCurrentDataSourceChanged(mpb, dsd
is called. Session will translate dsd to the media item and calls
onCurrentMediaItemChanged().

Following changes are also included
  - Removed MediaPlaylistController#getCurrentPlaylistItem(),
    because currently playing item is managed by the MediaPlayerBase.
  - Renamed ControllerCallback#onCurrentPlaylistItemChanged() to the
    ControllerCallback#onCurrentMediaItemChanged(), to make it more
    obvious that the event is from MediaPlayerBase, not
    MediaPlaylistController.
  - Added SessionCallback#onCurrentMediaItemChanged()

Bug: 64098437
Test: Run MediaComponents test
Change-Id: I78b124a7da0f968b097b2576507b9a73e36081ec

api/current.txt

@@ -23357,7 +23357,7 @@ package android.media {
     method public void close();
     method public void fastForward();
     method public long getBufferedPosition();
-    method public android.media.MediaItem2 getCurrentPlaylistItem();
+    method public android.media.MediaItem2 getCurrentMediaItem();
     method public android.media.MediaController2.PlaybackInfo getPlaybackInfo();
     method public float getPlaybackSpeed();
     method public int getPlayerState();
@@ -23403,7 +23403,7 @@ package android.media {
     method public void onAllowedCommandsChanged(android.media.MediaController2, android.media.MediaSession2.CommandGroup);
     method public void onBufferedPositionChanged(android.media.MediaController2, long);
     method public void onConnected(android.media.MediaController2, android.media.MediaSession2.CommandGroup);
-    method public void onCurrentPlaylistItemChanged(android.media.MediaController2, android.media.MediaItem2);
+    method public void onCurrentMediaItemChanged(android.media.MediaController2, android.media.MediaItem2);
     method public void onCustomCommand(android.media.MediaController2, android.media.MediaSession2.Command, android.os.Bundle, android.os.ResultReceiver);
     method public void onCustomLayoutChanged(android.media.MediaController2, java.util.List<android.media.MediaSession2.CommandButton>);
     method public void onDisconnected(android.media.MediaController2);
@@ -24543,7 +24543,6 @@ package android.media {
 
   public abstract interface MediaPlaylistController {
     method public abstract void addPlaylistItem(int, android.media.MediaItem2);
-    method public abstract android.media.MediaItem2 getCurrentPlaylistItem();
     method public abstract java.util.List<android.media.MediaItem2> getPlaylist();
     method public abstract android.media.MediaMetadata2 getPlaylistMetadata();
     method public abstract int getRepeatMode();
@@ -24856,7 +24855,7 @@ package android.media {
     method public void close();
     method public void fastForward();
     method public java.util.List<android.media.MediaSession2.ControllerInfo> getConnectedControllers();
-    method public android.media.MediaItem2 getCurrentPlaylistItem();
+    method public android.media.MediaItem2 getCurrentMediaItem();
     method public android.media.MediaPlaylistController getMediaPlaylistController();
     method public float getPlaybackSpeed();
     method public android.media.MediaPlayerBase getPlayer();
@@ -24999,6 +24998,7 @@ package android.media {
     method public void onBufferingStateChanged(android.media.MediaSession2, android.media.MediaPlayerBase, android.media.MediaItem2, int);
     method public boolean onCommandRequest(android.media.MediaSession2, android.media.MediaSession2.ControllerInfo, android.media.MediaSession2.Command);
     method public android.media.MediaSession2.CommandGroup onConnect(android.media.MediaSession2, android.media.MediaSession2.ControllerInfo);
+    method public void onCurrentMediaItemChanged(android.media.MediaSession2, android.media.MediaPlayerBase, android.media.MediaItem2);
     method public void onCustomCommand(android.media.MediaSession2, android.media.MediaSession2.ControllerInfo, android.media.MediaSession2.Command, android.os.Bundle, android.os.ResultReceiver);
     method public void onDisconnected(android.media.MediaSession2, android.media.MediaSession2.ControllerInfo);
     method public void onMediaPrepared(android.media.MediaSession2, android.media.MediaPlayerBase, android.media.MediaItem2);

media/java/android/media/MediaController2.java

@@ -146,7 +146,7 @@ public class MediaController2 implements AutoCloseable, MediaPlaylistController
          * @param playlist A new playlist set by the session.
          * @see #onPositionChanged(MediaController2, long, long)
          * @see #onBufferedPositionChanged(MediaController2, long)
-         * @see #onCurrentPlaylistItemChanged(MediaController2, MediaItem2)
+         * @see #onCurrentMediaItemChanged(MediaController2, MediaItem2)
          * @hide
          */
         // TODO(jaewan): Remove (b/74174728)
@@ -211,7 +211,7 @@ public class MediaController2 implements AutoCloseable, MediaPlaylistController
                 @Nullable Bundle extras) { }
 
         /**
-         * Called when the player's current playing item is changed
+         * Called when the player's currently playing item is changed
          * <p>
          * When it's called, you should invalidate previous playback information and wait for later
          * callbacks.
@@ -220,9 +220,8 @@ public class MediaController2 implements AutoCloseable, MediaPlaylistController
          * @param item new item
          * @see #onPositionChanged(MediaController2, long, long)
          * @see #onBufferedPositionChanged(MediaController2, long)
-         * @see #onCurrentPlaylistItemChanged(MediaController2, MediaItem2)
          */
-        public void onCurrentPlaylistItemChanged(@NonNull MediaController2 controller,
+        public void onCurrentMediaItemChanged(@NonNull MediaController2 controller,
                 @NonNull MediaItem2 item) { }
 
         /**
@@ -808,12 +807,12 @@ public class MediaController2 implements AutoCloseable, MediaPlaylistController
 
     /**
      * Get the lastly cached current item from
-     * {@link ControllerCallback#onCurrentPlaylistItemChanged(MediaController2, MediaItem2)}.
+     * {@link ControllerCallback#onCurrentMediaItemChanged(MediaController2, MediaItem2)}.
      *
      * @return index of the current item
      */
-    @Override
-    public MediaItem2 getCurrentPlaylistItem() {
+    public MediaItem2 getCurrentMediaItem() {
+        // TODO(jaewan): Rename provider API
         return mProvider.getCurrentPlaylistItem_impl();
     }
 

media/java/android/media/MediaPlaylistController.java

@@ -212,12 +212,6 @@ public interface MediaPlaylistController {
      */
     void replacePlaylistItem(int index, @NonNull MediaItem2 item);
 
-    /**
-     * Returns the current media item.
-     * @return the current media item, or null if none is set, or none available to play.
-     */
-    MediaItem2 getCurrentPlaylistItem();
-
     /**
      * Skips to the the media item, and plays from it.
      *

media/java/android/media/MediaSession2.java

@@ -778,6 +778,19 @@ public class MediaSession2 implements AutoCloseable, MediaPlaylistController {
         public void onPrepareFromUri(@NonNull MediaSession2 session,
                 @NonNull ControllerInfo controller, @NonNull Uri uri, @Nullable Bundle extras) { }
 
+        /**
+         * Called when the player's current playing item is changed
+         * <p>
+         * When it's called, you should invalidate previous playback information and wait for later
+         * callbacks.
+         *
+         * @param session the controller for this event
+         * @param mpb the player for this event
+         * @param item new item
+         */
+        public void onCurrentMediaItemChanged(@NonNull MediaSession2 session,
+                @NonNull MediaPlayerBase mpb, @NonNull MediaItem2 item) { }
+
         /**
          * Called when the player is <i>prepared</i>, i.e. it is ready to play the content
          * referenced by the given data source.
@@ -1753,8 +1766,8 @@ public class MediaSession2 implements AutoCloseable, MediaPlaylistController {
      *
      * @return currently playing media item
      */
-    @Override
-    public MediaItem2 getCurrentPlaylistItem() {
+    public MediaItem2 getCurrentMediaItem() {
+        // TODO(jaewan): Rename provider API
         return mProvider.getCurrentPlaylistItem_impl();
     }