-Fixed media session activation.

-Removed redundant setShuffle call in media session callback and its user.
-Removed unused dummy playback preparer.

app/src/main/java/org/schabi/newpipe/player/BasePlayer.java

@@ -271,6 +271,7 @@ public abstract class BasePlayer implements
         if (audioReactor != null) audioReactor.dispose();
         if (playbackManager != null) playbackManager.dispose();
         if (databaseUpdateReactor != null) databaseUpdateReactor.dispose();
+        if (mediaSessionManager != null) mediaSessionManager.dispose();
 
         if (playQueueAdapter != null) {
             playQueueAdapter.unsetSelectedListener();

app/src/main/java/org/schabi/newpipe/player/helper/MediaSessionManager.java

@@ -11,7 +11,6 @@ import android.view.KeyEvent;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.ext.mediasession.MediaSessionConnector;
 
-import org.schabi.newpipe.player.mediasession.DummyPlaybackPreparer;
 import org.schabi.newpipe.player.mediasession.MediaSessionCallback;
 import org.schabi.newpipe.player.mediasession.PlayQueueNavigator;
 import org.schabi.newpipe.player.mediasession.PlayQueuePlaybackController;
@@ -26,10 +25,12 @@ public class MediaSessionManager {
                                @NonNull final Player player,
                                @NonNull final MediaSessionCallback callback) {
         this.mediaSession = new MediaSessionCompat(context, TAG);
+        this.mediaSession.setActive(true);
+
         this.sessionConnector = new MediaSessionConnector(mediaSession,
                 new PlayQueuePlaybackController(callback));
         this.sessionConnector.setQueueNavigator(new PlayQueueNavigator(mediaSession, callback));
-        this.sessionConnector.setPlayer(player, new DummyPlaybackPreparer());
+        this.sessionConnector.setPlayer(player, null);
     }
 
     @Nullable
@@ -37,4 +38,11 @@ public class MediaSessionManager {
     public KeyEvent handleMediaButtonIntent(final Intent intent) {
         return MediaButtonReceiver.handleIntent(mediaSession, intent);
     }
+
+    public void dispose() {
+        this.sessionConnector.setPlayer(null, null);
+        this.sessionConnector.setQueueNavigator(null);
+        this.mediaSession.setActive(false);
+        this.mediaSession.release();
+    }
 }

app/src/main/java/org/schabi/newpipe/player/mediasession/DummyPlaybackPreparer.java

@@ -1,45 +0,0 @@
-package org.schabi.newpipe.player.mediasession;
-
-import android.net.Uri;
-import android.os.Bundle;
-import android.os.ResultReceiver;
-
-import com.google.android.exoplayer2.Player;
-import com.google.android.exoplayer2.ext.mediasession.MediaSessionConnector;
-
-public class DummyPlaybackPreparer implements MediaSessionConnector.PlaybackPreparer {
-    @Override
-    public long getSupportedPrepareActions() {
-        return 0;
-    }
-
-    @Override
-    public void onPrepare() {
-
-    }
-
-    @Override
-    public void onPrepareFromMediaId(String mediaId, Bundle extras) {
-
-    }
-
-    @Override
-    public void onPrepareFromSearch(String query, Bundle extras) {
-
-    }
-
-    @Override
-    public void onPrepareFromUri(Uri uri, Bundle extras) {
-
-    }
-
-    @Override
-    public String[] getCommands() {
-        return new String[0];
-    }
-
-    @Override
-    public void onCommand(Player player, String command, Bundle extras, ResultReceiver cb) {
-
-    }
-}

app/src/main/java/org/schabi/newpipe/player/mediasession/MediaSessionCallback.java

@@ -13,5 +13,4 @@ public interface MediaSessionCallback {
 
     void onPlay();
     void onPause();
-    void onSetShuffle(final boolean isShuffled);
 }

app/src/main/java/org/schabi/newpipe/player/mediasession/PlayQueuePlaybackController.java

@@ -1,7 +1,5 @@
 package org.schabi.newpipe.player.mediasession;
 
-import android.support.v4.media.session.PlaybackStateCompat;
-
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.ext.mediasession.DefaultPlaybackController;
 
@@ -22,10 +20,4 @@ public class PlayQueuePlaybackController extends DefaultPlaybackController {
     public void onPause(Player player) {
         callback.onPause();
     }
-
-    @Override
-    public void onSetShuffleMode(Player player, int shuffleMode) {
-        callback.onSetShuffle(shuffleMode == PlaybackStateCompat.SHUFFLE_MODE_ALL
-                || shuffleMode == PlaybackStateCompat.SHUFFLE_MODE_GROUP);
-    }
 }

app/src/main/java/org/schabi/newpipe/player/playback/BasePlayerMediaSession.java

@@ -69,9 +69,4 @@ public class BasePlayerMediaSession implements MediaSessionCallback {
     public void onPause() {
         player.onPause();
     }
-
-    @Override
-    public void onSetShuffle(boolean isShuffled) {
-        player.onShuffleModeEnabledChanged(isShuffled);
-    }
 }