Simple playback status and controls in Android Auto

Expose a MediaBrowserService from within the existing PlayerService,
and use the existing MediaSession for Auto.

Empty media browser for now.

To test, one needs to enable "Unknown sources" in Android Auto's
developer settings.

Issue: #1758

Author: haggaie

app/src/main/AndroidManifest.xml

@@ -64,6 +64,9 @@
             <intent-filter>
                 <action android:name="android.intent.action.MEDIA_BUTTON" />
             </intent-filter>
+            <intent-filter>
+                <action android:name="android.media.browse.MediaBrowserService"/>
+            </intent-filter>
         </service>
 
         <activity

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

@@ -21,37 +21,49 @@
 
 import static org.schabi.newpipe.util.Localization.assureCorrectAppLanguage;
 
-import android.app.Service;
 import android.content.Context;
 import android.content.Intent;
 import android.os.Binder;
+import android.os.Bundle;
 import android.os.IBinder;
+import android.support.v4.media.MediaBrowserCompat.MediaItem;
 import android.util.Log;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.media.MediaBrowserServiceCompat;
+
 import com.google.android.exoplayer2.ext.mediasession.MediaSessionConnector;
 
 import org.schabi.newpipe.player.mediabrowser.MediaBrowserConnector;
 import org.schabi.newpipe.player.mediasession.MediaSessionPlayerUi;
 import org.schabi.newpipe.util.ThemeHelper;
 
+import java.util.List;
+
+import io.reactivex.rxjava3.disposables.CompositeDisposable;
+
 /**
  * One service for all players.
  */
-public final class PlayerService extends Service {
+public final class PlayerService extends MediaBrowserServiceCompat {
     private static final String TAG = PlayerService.class.getSimpleName();
     private static final boolean DEBUG = Player.DEBUG;
 
     private Player player;
 
     private final IBinder mBinder = new LocalBinder();
     private MediaBrowserConnector mediaBrowserConnector;
+    private final CompositeDisposable compositeDisposableLoadChildren = new CompositeDisposable();
 
     /*//////////////////////////////////////////////////////////////////////////
     // Service's LifeCycle
     //////////////////////////////////////////////////////////////////////////*/
 
     @Override
     public void onCreate() {
+        super.onCreate();
+
         if (DEBUG) {
             Log.d(TAG, "onCreate() called");
         }
@@ -123,6 +135,7 @@ public void onDestroy() {
             mediaBrowserConnector.release();
             mediaBrowserConnector = null;
         }
+        compositeDisposableLoadChildren.clear();
     }
 
     private void cleanup() {
@@ -144,6 +157,9 @@ protected void attachBaseContext(final Context base) {
 
     @Override
     public IBinder onBind(final Intent intent) {
+        if (SERVICE_INTERFACE.equals(intent.getAction())) {
+            return super.onBind(intent);
+        }
         return mBinder;
     }
 
@@ -161,4 +177,21 @@ public Player getPlayer() {
             return PlayerService.this.player;
         }
     }
+
+    // MediaBrowserServiceCompat methods
+    @Nullable
+    @Override
+    public BrowserRoot onGetRoot(@NonNull final String clientPackageName, final int clientUid,
+                                 @Nullable final Bundle rootHints) {
+        return mediaBrowserConnector.onGetRoot(clientPackageName, clientUid, rootHints);
+    }
+
+    @Override
+    public void onLoadChildren(@NonNull final String parentId,
+                               @NonNull final Result<List<MediaItem>> result) {
+        result.detach();
+        final var disposable = mediaBrowserConnector.onLoadChildren(parentId)
+                .subscribe(result::sendResult);
+        compositeDisposableLoadChildren.add(disposable);
+    }
 }

app/src/main/java/org/schabi/newpipe/player/mediabrowser/MediaBrowserConnector.java

@@ -1,13 +1,26 @@
 package org.schabi.newpipe.player.mediabrowser;
 
+import static org.schabi.newpipe.MainActivity.DEBUG;
+
+import android.os.Bundle;
+import android.support.v4.media.MediaBrowserCompat;
+import android.support.v4.media.MediaBrowserCompat.MediaItem;
 import android.support.v4.media.session.MediaSessionCompat;
+import android.util.Log;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.media.MediaBrowserServiceCompat;
 
 import com.google.android.exoplayer2.ext.mediasession.MediaSessionConnector;
 
 import org.schabi.newpipe.player.PlayerService;
 
+import java.util.ArrayList;
+import java.util.List;
+
+import io.reactivex.rxjava3.core.Single;
+
 public class MediaBrowserConnector {
     private static final String TAG = MediaBrowserConnector.class.getSimpleName();
 
@@ -20,6 +33,7 @@ public MediaBrowserConnector(@NonNull final PlayerService playerService) {
         mediaSession = new MediaSessionCompat(playerService, TAG);
         sessionConnector = new MediaSessionConnector(mediaSession);
         sessionConnector.setMetadataDeduplicationEnabled(true);
+        playerService.setSessionToken(mediaSession.getSessionToken());
     }
 
     public @NonNull MediaSessionConnector getSessionConnector() {
@@ -29,4 +43,29 @@ public MediaBrowserConnector(@NonNull final PlayerService playerService) {
     public void release() {
         mediaSession.release();
     }
+
+    @NonNull
+    private static final String MY_MEDIA_ROOT_ID = "media_root_id";
+
+    @Nullable
+    public MediaBrowserServiceCompat.BrowserRoot onGetRoot(@NonNull final String clientPackageName,
+                                                           final int clientUid,
+                                                           @Nullable final Bundle rootHints) {
+        if (DEBUG) {
+            Log.d(TAG, String.format("MediaBrowserService.onGetRoot(%s, %s, %s)",
+                  clientPackageName, clientUid, rootHints));
+        }
+
+        return new MediaBrowserServiceCompat.BrowserRoot(MY_MEDIA_ROOT_ID, null);
+    }
+
+    public Single<List<MediaItem>> onLoadChildren(@NonNull final String parentId) {
+        if (DEBUG) {
+            Log.d(TAG, String.format("MediaBrowserService.onLoadChildren(%s)", parentId));
+        }
+
+        final List<MediaBrowserCompat.MediaItem> mediaItems = new ArrayList<>();
+
+        return Single.just(mediaItems);
+    }
 }