-Added shuffle button to background player.

-Extracted MediaSourceManager window size as parameter.
-Removed redundant list manipulation in PlayQueueAdapter.

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

@@ -84,7 +84,7 @@ public final class BackgroundPlayer extends Service {
     //////////////////////////////////////////////////////////////////////////*/
 
     public interface PlayerEventListener {
-        void onPlaybackUpdate(int state, int repeatMode, PlaybackParameters parameters);
+        void onPlaybackUpdate(int state, int repeatMode, boolean shuffled, PlaybackParameters parameters);
         void onProgressUpdate(int currentProgress, int duration, int bufferPercent);
         void onMetadataUpdate(StreamInfo info);
         void onServiceStopped();
@@ -340,8 +340,9 @@ public final class BackgroundPlayer extends Service {
         }
 
         @Override
-        public void onRepeatClicked() {
+        public void onShuffleClicked() {
-            super.onRepeatClicked();
+            super.onShuffleClicked();
+            updatePlayback();
         }
 
         @Override
@@ -491,7 +492,7 @@ public final class BackgroundPlayer extends Service {
 
         private void updatePlayback() {
             if (activityListener != null) {
-                activityListener.onPlaybackUpdate(currentState, simpleExoPlayer.getRepeatMode(), simpleExoPlayer.getPlaybackParameters());
+                activityListener.onPlaybackUpdate(currentState, simpleExoPlayer.getRepeatMode(), playQueue.isShuffled(), simpleExoPlayer.getPlaybackParameters());
             }
         }
 

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

@@ -72,6 +72,7 @@ public class BackgroundPlayerActivity extends AppCompatActivity
     private ImageButton backwardButton;
     private ImageButton playPauseButton;
     private ImageButton forwardButton;
+    private ImageButton shuffleButton;
 
     ////////////////////////////////////////////////////////////////////////////
     // Activity Lifecycle
@@ -196,11 +197,13 @@ public class BackgroundPlayerActivity extends AppCompatActivity
         backwardButton = rootView.findViewById(R.id.control_backward);
         playPauseButton = rootView.findViewById(R.id.control_play_pause);
         forwardButton = rootView.findViewById(R.id.control_forward);
+        shuffleButton = rootView.findViewById(R.id.control_shuffle);
 
         repeatButton.setOnClickListener(this);
         backwardButton.setOnClickListener(this);
         playPauseButton.setOnClickListener(this);
         forwardButton.setOnClickListener(this);
+        shuffleButton.setOnClickListener(this);
     }
 
     private void buildItemPopupMenu(final PlayQueueItem item, final View view) {
@@ -298,6 +301,10 @@ public class BackgroundPlayerActivity extends AppCompatActivity
         context.sendBroadcast(new Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS));
     }
 
+    private void scrollToSelected() {
+        itemsList.smoothScrollToPosition(player.playQueue.getIndex());
+    }
+
     ////////////////////////////////////////////////////////////////////////////
     // Component On-Click Listener
     ////////////////////////////////////////////////////////////////////////////
@@ -308,10 +315,14 @@ public class BackgroundPlayerActivity extends AppCompatActivity
             player.onRepeatClicked();
         } else if (view.getId() == backwardButton.getId()) {
             player.onPlayPrevious();
+            scrollToSelected();
         } else if (view.getId() == playPauseButton.getId()) {
             player.onVideoPlayPause();
+            scrollToSelected();
         } else if (view.getId() == forwardButton.getId()) {
             player.onPlayNext();
+        } else if (view.getId() == shuffleButton.getId()) {
+            player.onShuffleClicked();
         }
     }
 
@@ -340,7 +351,7 @@ public class BackgroundPlayerActivity extends AppCompatActivity
     ////////////////////////////////////////////////////////////////////////////
 
     @Override
-    public void onPlaybackUpdate(int state, int repeatMode, PlaybackParameters parameters) {
+    public void onPlaybackUpdate(int state, int repeatMode, boolean shuffled, PlaybackParameters parameters) {
         switch (state) {
             case BasePlayer.STATE_PAUSED:
                 playPauseButton.setImageResource(R.drawable.ic_play_arrow_white);
@@ -355,29 +366,41 @@ public class BackgroundPlayerActivity extends AppCompatActivity
                 break;
         }
 
-        int alpha = 255;
+        int repeatAlpha = 255;
         switch (repeatMode) {
             case Player.REPEAT_MODE_OFF:
-                alpha = 77;
+                repeatAlpha = 77;
                 break;
             case Player.REPEAT_MODE_ONE:
                 // todo change image
-                alpha = 168;
+                repeatAlpha = 168;
                 break;
             case Player.REPEAT_MODE_ALL:
-                alpha = 255;
+                repeatAlpha = 255;
                 break;
         }
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
-            repeatButton.setImageAlpha(alpha);
+            repeatButton.setImageAlpha(repeatAlpha);
         } else {
-            repeatButton.setAlpha(alpha);
+            repeatButton.setAlpha(repeatAlpha);
+        }
+
+        int shuffleAlpha = 255;
+        if (!shuffled) {
+            shuffleAlpha = 77;
+        }
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
+            shuffleButton.setImageAlpha(shuffleAlpha);
+        } else {
+            shuffleButton.setAlpha(shuffleAlpha);
         }
 
         if (parameters != null) {
             final float speed = parameters.speed;
             final float pitch = parameters.pitch;
         }
+
+        scrollToSelected();
     }
 
     @Override
@@ -401,6 +424,7 @@ public class BackgroundPlayerActivity extends AppCompatActivity
         if (info != null) {
             metadataTitle.setText(info.name);
             metadataArtist.setText(info.uploader_name);
+            scrollToSelected();
         }
     }
 

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

@@ -535,7 +535,7 @@ public abstract class BasePlayer implements Player.EventListener,
     }
 
     /*//////////////////////////////////////////////////////////////////////////
-    // Repeat
+    // Repeat and shuffle
     //////////////////////////////////////////////////////////////////////////*/
 
     public void onRepeatClicked() {
@@ -560,6 +560,18 @@ public abstract class BasePlayer implements Player.EventListener,
         if (DEBUG) Log.d(TAG, "onRepeatClicked() currentRepeatMode = " + simpleExoPlayer.getRepeatMode());
     }
 
+    public void onShuffleClicked() {
+        if (DEBUG) Log.d(TAG, "onShuffleClicked() called");
+
+        if (playQueue == null) return;
+
+        if (playQueue.isShuffled()) {
+            playQueue.unshuffle();
+        } else {
+            playQueue.shuffle();
+        }
+    }
+
     /*//////////////////////////////////////////////////////////////////////////
     // ExoPlayer Listener
     //////////////////////////////////////////////////////////////////////////*/

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

@@ -12,13 +12,11 @@ import org.schabi.newpipe.extractor.stream.StreamInfo;
 import org.schabi.newpipe.player.mediasource.DeferredMediaSource;
 import org.schabi.newpipe.playlist.PlayQueue;
 import org.schabi.newpipe.playlist.PlayQueueItem;
-import org.schabi.newpipe.playlist.events.ErrorEvent;
 import org.schabi.newpipe.playlist.events.MoveEvent;
 import org.schabi.newpipe.playlist.events.PlayQueueMessage;
 import org.schabi.newpipe.playlist.events.RemoveEvent;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 import io.reactivex.android.schedulers.AndroidSchedulers;
@@ -29,10 +27,8 @@ import io.reactivex.functions.Consumer;
 public class MediaSourceManager implements DeferredMediaSource.Callback {
     private final String TAG = "MediaSourceManager@" + Integer.toHexString(hashCode());
     // One-side rolling window size for default loading
-    // Effectively loads WINDOW_SIZE * 2 + 1 streams, must be greater than 0
+    // Effectively loads windowSize * 2 + 1 streams, must be greater than 0
-    // todo: inject this parameter, allow user settings perhaps
+    private final int windowSize;
-    private static final int WINDOW_SIZE = 1;
-
     private PlaybackListener playbackListener;
     private PlayQueue playQueue;
 
@@ -45,8 +41,15 @@ public class MediaSourceManager implements DeferredMediaSource.Callback {
 
     public MediaSourceManager(@NonNull final PlaybackListener listener,
                               @NonNull final PlayQueue playQueue) {
+        this(listener, playQueue, 1);
+    }
+
+    public MediaSourceManager(@NonNull final PlaybackListener listener,
+                              @NonNull final PlayQueue playQueue,
+                              final int windowSize) {
         this.playbackListener = listener;
         this.playQueue = playQueue;
+        this.windowSize = windowSize;
 
         this.syncReactor = new SerialDisposable();
 
@@ -85,7 +88,7 @@ public class MediaSourceManager implements DeferredMediaSource.Callback {
     }
 
     /**
-     * Loads the current playing stream and the streams within its WINDOW_SIZE bound.
+     * Loads the current playing stream and the streams within its windowSize bound.
      *
      * Unblocks the player once the item at the current index is loaded.
      * */
@@ -97,8 +100,8 @@ public class MediaSourceManager implements DeferredMediaSource.Callback {
         load(currentItem);
 
         // The rest are just for seamless playback
-        final int leftBound = Math.max(0, currentIndex - WINDOW_SIZE);
+        final int leftBound = Math.max(0, currentIndex - windowSize);
-        final int rightLimit = currentIndex + WINDOW_SIZE + 1;
+        final int rightLimit = currentIndex + windowSize + 1;
         final int rightBound = Math.min(playQueue.size(), rightLimit);
         final List<PlayQueueItem> items = new ArrayList<>(playQueue.getStreams().subList(leftBound, rightBound));
 
@@ -119,6 +122,10 @@ public class MediaSourceManager implements DeferredMediaSource.Callback {
         populateSources();
     }
 
+    public int getWindowSize() {
+        return windowSize;
+    }
+
     /*//////////////////////////////////////////////////////////////////////////
     // Event Reactor
     //////////////////////////////////////////////////////////////////////////*/
@@ -188,7 +195,7 @@ public class MediaSourceManager implements DeferredMediaSource.Callback {
     //////////////////////////////////////////////////////////////////////////*/
 
     private boolean isPlayQueueReady() {
-        return playQueue.isComplete() || playQueue.size() - playQueue.getIndex() > WINDOW_SIZE;
+        return playQueue.isComplete() || playQueue.size() - playQueue.getIndex() > windowSize;
     }
 
     private boolean tryBlock() {

app/src/main/java/org/schabi/newpipe/playlist/PlayQueue.java

@@ -222,6 +222,8 @@ public abstract class PlayQueue implements Serializable {
      * */
     public synchronized void append(final PlayQueueItem... items) {
         streams.addAll(Arrays.asList(items));
+        if (backup != null) backup.addAll(Arrays.asList(items));
+
         broadcast(new AppendEvent(items.length));
     }
 
@@ -232,6 +234,8 @@ public abstract class PlayQueue implements Serializable {
      * */
     public synchronized void append(final Collection<PlayQueueItem> items) {
         streams.addAll(items);
+        if (backup != null) backup.addAll(items);
+
         broadcast(new AppendEvent(items.size()));
     }
 
@@ -271,6 +275,10 @@ public abstract class PlayQueue implements Serializable {
         }
 
         streams.remove(index);
+        if (backup != null) {
+            final int backupIndex = backup.indexOf(getItem(index));
+            backup.remove(backupIndex);
+        }
     }
 
     public synchronized void move(final int source, final int target) {
@@ -300,7 +308,9 @@ public abstract class PlayQueue implements Serializable {
      * Will emit a {@link ReorderEvent} in any context.
      * */
     public synchronized void shuffle() {
-        backup = new ArrayList<>(streams);
+        if (backup == null) {
+            backup = new ArrayList<>(streams);
+        }
         final PlayQueueItem current = getItem();
         Collections.shuffle(streams);
         queueIndex.set(streams.indexOf(current));

app/src/main/java/org/schabi/newpipe/playlist/PlayQueueAdapter.java

@@ -72,18 +72,6 @@ public class PlayQueueAdapter extends RecyclerView.Adapter<RecyclerView.ViewHold
         playQueueItemBuilder.setOnSelectedListener(listener);
     }
 
-    public void add(final List<PlayQueueItem> data) {
-        playQueue.append(data);
-    }
-
-    public void add(final PlayQueueItem... data) {
-        playQueue.append(data);
-    }
-
-    public void remove(final int index) {
-        playQueue.remove(index);
-    }
-
     private void startReactor() {
         final Observer<PlayQueueMessage> observer = new Observer<PlayQueueMessage>() {
             @Override

app/src/main/res/layout/activity_background_player.xml

@@ -126,23 +126,22 @@
             android:id="@+id/control_repeat"
             android:layout_width="25dp"
             android:layout_height="25dp"
-            android:layout_alignParentLeft="true"
+            android:layout_toLeftOf="@+id/control_backward"
-            android:layout_alignParentStart="true"
             android:layout_centerVertical="true"
-            android:layout_marginLeft="8dp"
+            android:layout_marginLeft="5dp"
             android:background="#00000000"
             android:clickable="true"
             android:focusable="true"
             android:scaleType="fitXY"
             android:src="@drawable/ic_repeat_white"
-            tools:ignore="ContentDescription" />
+            tools:ignore="ContentDescription"/>
 
         <ImageButton
             android:id="@+id/control_backward"
             android:layout_width="40dp"
             android:layout_height="match_parent"
             android:layout_centerVertical="true"
-            android:layout_marginRight="5dp"
+            android:layout_marginLeft="5dp"
             android:layout_toLeftOf="@+id/control_play_pause"
             android:background="#00000000"
             android:clickable="true"
@@ -157,8 +156,10 @@
             android:layout_width="50dp"
             android:layout_height="match_parent"
             android:layout_centerVertical="true"
+            android:layout_centerHorizontal="true"
+            android:layout_centerInParent="true"
+            android:layout_marginLeft="5dp"
             android:layout_marginRight="5dp"
-            android:layout_toLeftOf="@+id/control_forward"
             android:background="#00000000"
             android:padding="2dp"
             android:clickable="true"
@@ -171,9 +172,9 @@
             android:id="@+id/control_forward"
             android:layout_width="40dp"
             android:layout_height="match_parent"
-            android:layout_alignParentRight="true"
             android:layout_centerVertical="true"
-            android:layout_marginRight="8dp"
+            android:layout_marginRight="5dp"
+            android:layout_toRightOf="@+id/control_play_pause"
             android:background="#00000000"
             android:clickable="true"
             android:focusable="true"
@@ -181,6 +182,20 @@
             android:scaleType="fitCenter"
             android:src="@drawable/ic_action_av_fast_forward"
             tools:ignore="ContentDescription"/>
+
+        <ImageButton
+            android:id="@+id/control_shuffle"
+            android:layout_width="25dp"
+            android:layout_height="25dp"
+            android:layout_toRightOf="@+id/control_forward"
+            android:layout_centerVertical="true"
+            android:layout_marginRight="5dp"
+            android:background="#00000000"
+            android:clickable="true"
+            android:focusable="true"
+            android:scaleType="fitXY"
+            android:src="@drawable/ic_palette_white_24dp"
+            tools:ignore="ContentDescription"/>
     </RelativeLayout>
 
 </RelativeLayout>