Fix playing music in bg when sign out

app/src/main/java/com/oscarliang/spotifyclone/MainActivity.java

@@ -14,6 +14,7 @@
 import androidx.navigation.ui.NavigationUI;
 
 import com.oscarliang.spotifyclone.core.auth.AuthManager;
+import com.oscarliang.spotifyclone.core.player.MusicPlayer;
 import com.oscarliang.spotifyclone.databinding.ActivityMainBinding;
 
 import java.util.Objects;
@@ -35,6 +36,9 @@ public class MainActivity extends AppCompatActivity implements HasAndroidInjecto
     @Inject
     AuthManager authManager;
 
+    @Inject
+    MusicPlayer musicPlayer;
+
     private ActivityMainBinding binding;
     private NavController navController;
     private View navView;
@@ -79,8 +83,7 @@ private void initToolbar() {
     private void initDrawer() {
         binding.drawer.navView.setNavigationItemSelectedListener(item -> {
             if (item.getItemId() == R.id.action_logout) {
-                authManager.signOut();
-                navigateWelcomeFragment();
+                signOut();
             }
             item.setChecked(true);
             binding.drawerLayout.close();
@@ -172,6 +175,16 @@ private void subscribeAuthState() {
         );
     }
 
+    private void signOut() {
+        // Clear all the music to prevent playing
+        // the music in bg when user is not log in
+        musicPlayer.clearMusic();
+
+        // Sign out and navigate to welcome page
+        authManager.signOut();
+        navigateWelcomeFragment();
+    }
+
     private void navigateWelcomeFragment() {
         // Pop up all the backstack to prevent navigating back
         navController.navigate(

core/player/src/main/java/com/oscarliang/spotifyclone/core/player/ExoMusicPlayer.java

@@ -200,6 +200,15 @@ public void addPlaylist(@NonNull List<Music> musics, @NonNull String playlistId)
         this.musics.onNext(musics);
     }
 
+    @Override
+    public void clearMusic() {
+        // Stop the current music and clear all the media items.
+        // Note that we do not call release(), or the player
+        // will be unavailable when later the user re-login.
+        mediaController.stop();
+        mediaController.clearMediaItems();
+    }
+
     private MediaItem createMediaItem(Music music) {
         return new MediaItem.Builder()
                 .setMediaId(music.getId())

core/player/src/main/java/com/oscarliang/spotifyclone/core/player/MusicPlayer.java

@@ -37,4 +37,6 @@ public interface MusicPlayer {
 
     void addPlaylist(@NonNull List<Music> musics, @NonNull String playlistId);
 
+    void clearMusic();
+
 }