Start playback from notification

This change fixes two bugs where MediaSessionServe shows a notification
with the Play icon but tapping it will not start playback:
1. After playback ends: we need to seek to the beginning of the media
   item.
2. After adding media items to the player but not starting playback:
   We need to call Player.prepare() too.

PiperOrigin-RevId: 432469953
(cherry picked from commit 1023b9d55efe8f0470c5f3b75cd84e40860f79be)

demos/session/src/main/java/androidx/media3/demo/session/PlayableFolderActivity.kt

@@ -30,6 +30,7 @@ import android.widget.ListView
 import android.widget.TextView
 import androidx.appcompat.app.AppCompatActivity
 import androidx.media3.common.MediaItem
+import androidx.media3.common.Player
 import androidx.media3.session.MediaBrowser
 import androidx.media3.session.SessionToken
 import com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton
@@ -179,6 +180,9 @@ class PlayableFolderActivity : AppCompatActivity() {
       returnConvertView.findViewById<TextView>(R.id.add_button).setOnClickListener {
         val browser = this@PlayableFolderActivity.browser ?: return@setOnClickListener
         browser.addMediaItem(mediaItem)
+        if (browser.playbackState == Player.STATE_IDLE) {
+          browser.prepare()
+        }
         Snackbar.make(
             findViewById<LinearLayout>(R.id.linear_layout),
             getString(R.string.added_media_item_format, mediaItem.mediaMetadata.title),

demos/session/src/main/java/androidx/media3/demo/session/PlaybackService.kt

@@ -96,7 +96,6 @@ class PlaybackService : MediaLibraryService() {
 
       val item = MediaItemTree.getItemFromTitle(mediaTitle) ?: MediaItemTree.getRandomItem()
       player.setMediaItem(item)
-      player.prepare()
     }
 
     override fun onSetMediaUri(

libraries/session/src/main/java/androidx/media3/session/DefaultMediaNotificationProvider.java

@@ -27,6 +27,7 @@ import android.os.Bundle;
 import androidx.core.app.NotificationCompat;
 import androidx.core.graphics.drawable.IconCompat;
 import androidx.media3.common.MediaMetadata;
+import androidx.media3.common.Player;
 import androidx.media3.common.util.UnstableApi;
 import androidx.media3.common.util.Util;
 
@@ -93,20 +94,21 @@ import androidx.media3.common.util.Util;
             IconCompat.createWithResource(context, R.drawable.media3_notification_seek_to_previous),
             context.getString(R.string.media3_controls_seek_to_previous_description),
             MediaNotification.ActionFactory.COMMAND_SKIP_TO_PREVIOUS));
-    if (mediaController.getPlayWhenReady()) {
+    if (mediaController.getPlaybackState() == Player.STATE_ENDED
-      // Pause action.
+        || !mediaController.getPlayWhenReady()) {
-      builder.addAction(
-          actionFactory.createMediaAction(
-              IconCompat.createWithResource(context, R.drawable.media3_notification_pause),
-              context.getString(R.string.media3_controls_pause_description),
-              MediaNotification.ActionFactory.COMMAND_PAUSE));
-    } else {
       // Play action.
       builder.addAction(
           actionFactory.createMediaAction(
               IconCompat.createWithResource(context, R.drawable.media3_notification_play),
               context.getString(R.string.media3_controls_play_description),
               MediaNotification.ActionFactory.COMMAND_PLAY));
+    } else {
+      // Pause action.
+      builder.addAction(
+          actionFactory.createMediaAction(
+              IconCompat.createWithResource(context, R.drawable.media3_notification_pause),
+              context.getString(R.string.media3_controls_pause_description),
+              MediaNotification.ActionFactory.COMMAND_PAUSE));
     }
     // Skip to next action.
     builder.addAction(

libraries/session/src/main/java/androidx/media3/session/MediaNotificationManager.java

@@ -196,7 +196,9 @@ import java.util.concurrent.TimeoutException;
     @Override
     public void onEvents(Player player, Player.Events events) {
       if (events.containsAny(
-          Player.EVENT_PLAY_WHEN_READY_CHANGED, Player.EVENT_MEDIA_METADATA_CHANGED)) {
+          Player.EVENT_PLAYBACK_STATE_CHANGED,
+          Player.EVENT_PLAY_WHEN_READY_CHANGED,
+          Player.EVENT_MEDIA_METADATA_CHANGED)) {
         updateNotification(session);
       }
     }

libraries/session/src/main/java/androidx/media3/session/MediaSessionLegacyStub.java

@@ -28,6 +28,8 @@ import static androidx.media3.common.Player.COMMAND_SET_REPEAT_MODE;
 import static androidx.media3.common.Player.COMMAND_SET_SHUFFLE_MODE;
 import static androidx.media3.common.Player.COMMAND_SET_SPEED_AND_PITCH;
 import static androidx.media3.common.Player.COMMAND_STOP;
+import static androidx.media3.common.Player.STATE_ENDED;
+import static androidx.media3.common.Player.STATE_IDLE;
 import static androidx.media3.common.util.Assertions.checkNotNull;
 import static androidx.media3.common.util.Assertions.checkStateNotNull;
 import static androidx.media3.common.util.Util.postOrRun;
@@ -231,7 +233,17 @@ import org.checkerframework.checker.initialization.qual.Initialized;
     } else {
       dispatchSessionTaskWithPlayerCommand(
           COMMAND_PLAY_PAUSE,
-          (controller) -> sessionImpl.getPlayerWrapper().play(),
+          (controller) -> {
+            PlayerWrapper playerWrapper = sessionImpl.getPlayerWrapper();
+            @Player.State int playbackState = playerWrapper.getPlaybackState();
+            if (playbackState == STATE_IDLE) {
+              playerWrapper.prepare();
+            } else if (playbackState == STATE_ENDED) {
+              playerWrapper.seekTo(
+                  playerWrapper.getCurrentMediaItemIndex(), /* positionMs= */ C.TIME_UNSET);
+            }
+            playerWrapper.play();
+          },
           remoteUserInfo);
     }
   }
@@ -285,7 +297,17 @@ import org.checkerframework.checker.initialization.qual.Initialized;
   public void onPlay() {
     dispatchSessionTaskWithPlayerCommand(
         COMMAND_PLAY_PAUSE,
-        controller -> sessionImpl.getPlayerWrapper().play(),
+        controller -> {
+          PlayerWrapper playerWrapper = sessionImpl.getPlayerWrapper();
+          @Player.State int playbackState = playerWrapper.getPlaybackState();
+          if (playbackState == Player.STATE_IDLE) {
+            playerWrapper.prepare();
+          } else if (playbackState == Player.STATE_ENDED) {
+            playerWrapper.seekTo(
+                playerWrapper.getCurrentMediaItemIndex(), /* positionMs= */ C.TIME_UNSET);
+          }
+          playerWrapper.play();
+        },
         sessionCompat.getCurrentControllerInfo());
   }
 
@@ -321,7 +343,15 @@ import org.checkerframework.checker.initialization.qual.Initialized;
           if (sessionImpl.onSetMediaUriOnHandler(
                   controller, mediaUri, extras == null ? Bundle.EMPTY : extras)
               == RESULT_SUCCESS) {
-            sessionImpl.getPlayerWrapper().play();
+            PlayerWrapper playerWrapper = sessionImpl.getPlayerWrapper();
+            @Player.State int playbackState = playerWrapper.getPlaybackState();
+            if (playbackState == Player.STATE_IDLE) {
+              playerWrapper.prepare();
+            } else if (playbackState == STATE_ENDED) {
+              playerWrapper.seekTo(
+                  playerWrapper.getCurrentMediaItemIndex(), /* positionMs= */ C.TIME_UNSET);
+            }
+            playerWrapper.play();
           }
         });
   }