-Added on change event bus to Play Queue.

-Added playback manager for player interaction.

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

@@ -47,9 +47,7 @@ import com.google.android.exoplayer2.RenderersFactory;
 import com.google.android.exoplayer2.SimpleExoPlayer;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.extractor.DefaultExtractorsFactory;
-import com.google.android.exoplayer2.source.DynamicConcatenatingMediaSource;
 import com.google.android.exoplayer2.source.ExtractorMediaSource;
-import com.google.android.exoplayer2.source.LoopingMediaSource;
 import com.google.android.exoplayer2.source.MediaSource;
 import com.google.android.exoplayer2.source.TrackGroupArray;
 import com.google.android.exoplayer2.source.dash.DashMediaSource;
@@ -72,6 +70,7 @@ import com.nostra13.universalimageloader.core.listener.SimpleImageLoadingListene
 
 import org.schabi.newpipe.Downloader;
 import org.schabi.newpipe.R;
+import org.schabi.newpipe.playlist.PlayQueue;
 
 import java.io.File;
 import java.text.DecimalFormat;
@@ -86,9 +85,9 @@ import java.util.concurrent.atomic.AtomicBoolean;
  * @author mauriciocolli
  */
 @SuppressWarnings({"WeakerAccess", "unused"})
-public abstract class BasePlayer implements Player.EventListener, AudioManager.OnAudioFocusChangeListener {
+public abstract class BasePlayer implements Player.EventListener,
+        AudioManager.OnAudioFocusChangeListener, PlaybackManager.PlaybackListener {
     // TODO: Check api version for deprecated audio manager methods
-
     public static final boolean DEBUG = false;
     public static final String TAG = "BasePlayer";
 
@@ -117,6 +116,13 @@ public abstract class BasePlayer implements Player.EventListener, AudioManager.O
     protected long videoStartPos = -1;
     protected String uploaderName = "";
 
+    /*//////////////////////////////////////////////////////////////////////////
+    // Playlist
+    //////////////////////////////////////////////////////////////////////////*/
+
+    protected PlaybackManager playbackManager;
+    protected PlayQueue playQueue;
+
     /*//////////////////////////////////////////////////////////////////////////
     // Player
     //////////////////////////////////////////////////////////////////////////*/
@@ -540,6 +546,22 @@ public abstract class BasePlayer implements Player.EventListener, AudioManager.O
 
     @Override
     public void onPositionDiscontinuity() {
+        int newIndex = simpleExoPlayer.getCurrentWindowIndex();
+
+    }
+
+    /*//////////////////////////////////////////////////////////////////////////
+    // Playback Listener
+    //////////////////////////////////////////////////////////////////////////*/
+
+    @Override
+    public void block() {
+        if (currentState != STATE_LOADING) changeState(STATE_LOADING);
+    }
+
+    @Override
+    public void unblock() {
+        if (currentState != STATE_PLAYING) changeState(STATE_PLAYING);
     }
 
     /*//////////////////////////////////////////////////////////////////////////

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

@@ -3,31 +3,200 @@ package org.schabi.newpipe.player;
 import com.google.android.exoplayer2.source.DynamicConcatenatingMediaSource;
 import com.google.android.exoplayer2.source.MediaSource;
 
+import org.reactivestreams.Subscriber;
+import org.reactivestreams.Subscription;
+import org.schabi.newpipe.extractor.stream_info.StreamInfo;
 import org.schabi.newpipe.playlist.PlayQueue;
+import org.schabi.newpipe.playlist.PlayQueueEvent;
+import org.schabi.newpipe.playlist.PlayQueueItem;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
+import io.reactivex.Maybe;
+import io.reactivex.annotations.NonNull;
+
 public class PlaybackManager {
 
-    private DynamicConcatenatingMediaSource source;
+    private DynamicConcatenatingMediaSource mediaSource;
+    private List<PlayQueueItem> queueSource;
+    private int sourceIndex;
 
+    private PlaybackListener listener;
     private PlayQueue playQueue;
-    private int index;
-
-    private List<MediaSource> sources;
-
-    public PlaybackManager(PlayQueue playQueue, int index) {
-        this.source = new DynamicConcatenatingMediaSource();
-
-        this.playQueue = playQueue;
-        this.index = index;
 
+    private Subscription playQueueReactor;
 
+    interface PlaybackListener {
+        void block();
+        void unblock();
+        void sync();
 
+        MediaSource sourceOf(StreamInfo info);
     }
 
-    interface OnChangeListener {
+    public PlaybackManager(@NonNull final PlaybackListener listener,
-        void isLoading();
+                           @NonNull final PlayQueue playQueue) {
-        void isLoaded();
+        this.mediaSource = new DynamicConcatenatingMediaSource();
+        this.queueSource = Collections.synchronizedList(new ArrayList<PlayQueueItem>(10));
+        this.sourceIndex = 0;
+
+        this.listener = listener;
+        this.playQueue = playQueue;
+
+        playQueue.getPlayQueueFlowable().subscribe(getReactor());
+    }
+
+    @NonNull
+    public DynamicConcatenatingMediaSource getMediaSource() {
+        return mediaSource;
+    }
+
+    private void reload() {
+        listener.block();
+        load(0);
+    }
+
+    public void refreshMedia(final int newMediaIndex) {
+        if (newMediaIndex == sourceIndex) return;
+
+        if (newMediaIndex == sourceIndex + 1) {
+            playQueue.incrementIndex();
+            mediaSource.removeMediaSource(0);
+            queueSource.remove(0);
+        } else {
+            //something went wrong
+            onInit();
+        }
+    }
+
+    private void removeCurrent() {
+        listener.block();
+        mediaSource.removeMediaSource(0);
+        queueSource.remove(0);
+        listener.unblock();
+    }
+
+    private Subscription loaderReactor;
+
+    private void load() {
+        if (mediaSource.getSize() < 5 && queueSource.size() < 5) load(mediaSource.getSize());
+    }
+
+    private void load(final int from) {
+        clear(from);
+
+        if (loaderReactor != null) loaderReactor.cancel();
+
+        List<Maybe<StreamInfo>> maybes = new ArrayList<>();
+        for (int i = from; i < 5; i++) {
+            final int index = playQueue.getIndex() + i;
+            final PlayQueueItem item = playQueue.get(index);
+            queueSource.set(i, item);
+            maybes.add(item.getStream());
+        }
+
+        Maybe.concat(maybes).subscribe(new Subscriber<StreamInfo>() {
+            @Override
+            public void onSubscribe(Subscription s) {
+                loaderReactor = s;
+            }
+
+            @Override
+            public void onNext(StreamInfo streamInfo) {
+                mediaSource.addMediaSource(listener.sourceOf(streamInfo));
+                onLoaded();
+            }
+
+            @Override
+            public void onError(Throwable t) {
+                playQueue.remove(queueSource.size());
+            }
+
+            @Override
+            public void onComplete() {
+            }
+        });
+    }
+
+    private void onLoaded() {
+        if (mediaSource.getSize() > 0 && queueSource.size() > 0) listener.unblock();
+    }
+
+    private void onInit() {
+        listener.block();
+        load();
+    }
+
+    private void clear(int from) {
+        listener.block();
+        while (mediaSource.getSize() > from) {
+            queueSource.remove(from);
+            mediaSource.removeMediaSource(from);
+        }
+        listener.unblock();
+    }
+
+    private Subscriber<PlayQueueEvent> getReactor() {
+        return new Subscriber<PlayQueueEvent>() {
+            @Override
+            public void onSubscribe(@NonNull Subscription d) {
+                if (playQueueReactor != null) playQueueReactor.cancel();
+                playQueueReactor = d;
+                playQueueReactor.request(1);
+            }
+
+            @Override
+            public void onNext(@NonNull PlayQueueEvent event) {
+                if (playQueue.getStreams().size() - playQueue.getIndex() < 10 && !playQueue.isComplete()) {
+                    listener.block();
+                    playQueue.fetch();
+                }
+
+                switch (event) {
+                    case INIT:
+                        onInit();
+                        break;
+                    case APPEND:
+                        load();
+                        break;
+                    case REMOVE_CURRENT:
+                        removeCurrent();
+                        load();
+                        break;
+                    case SELECT:
+                        reload();
+                        break;
+                    case REMOVE:
+                    case SWAP:
+                        load(1);
+                        break;
+                    case CLEAR:
+                        clear(0);
+                        break;
+                    case NEXT:
+                    default:
+                        break;
+                }
+
+                onLoaded();
+                if (playQueueReactor != null) playQueueReactor.request(1);
+            }
+
+            @Override
+            public void onError(@NonNull Throwable e) {
+
+            }
+
+            @Override
+            public void onComplete() {
+                // Never completes, only canceled
+            }
+        };
+    }
+
+    public void dispose() {
+        if (playQueueReactor != null) playQueueReactor.cancel();
     }
 }

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

@@ -1,44 +1,45 @@
 package org.schabi.newpipe.playlist;
 
 import org.schabi.newpipe.extractor.InfoItem;
-import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.StreamingService;
-import org.schabi.newpipe.extractor.exceptions.ExtractionException;
 import org.schabi.newpipe.extractor.playlist.PlayListExtractor;
 import org.schabi.newpipe.extractor.playlist.PlayListInfo;
-import org.schabi.newpipe.extractor.playlist.PlayListInfoItem;
 import org.schabi.newpipe.extractor.stream_info.StreamInfo;
 import org.schabi.newpipe.extractor.stream_info.StreamInfoItem;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.Callable;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import io.reactivex.Maybe;
 import io.reactivex.android.schedulers.AndroidSchedulers;
+import io.reactivex.disposables.Disposable;
 import io.reactivex.functions.Consumer;
 import io.reactivex.schedulers.Schedulers;
 
 public class ExternalPlayQueue extends PlayQueue {
-
+    private final String TAG = "ExternalPlayQueue@" + Integer.toHexString(hashCode());
-    private final static int LOAD_PROXIMITY = 10;
 
     private boolean isComplete;
 
-    private AtomicInteger pageNumber;
-
     private StreamingService service;
+    private String playlistUrl;
 
-    private PlayListInfoItem playlist;
+    private AtomicInteger pageNumber;
+    private Disposable fetchReactor;
 
-    public ExternalPlayQueue(final PlayListInfoItem playlist) {
+    public ExternalPlayQueue(final String playlistUrl,
-        super();
+                             final PlayListInfo info,
-        this.service = getService(playlist.serviceId);
+                             final int nextPage,
-        this.pageNumber = new AtomicInteger(0);
+                             final int index) {
-        this.playlist = playlist;
+        super(index);
+        this.service = getService(info.service_id);
+        this.pageNumber = new AtomicInteger(nextPage);
+        this.playlistUrl = playlistUrl;
 
-        fetch();
+        getStreams().addAll(extractPlaylistItems(info));
     }
 
     @Override
@@ -47,36 +48,25 @@ public class ExternalPlayQueue extends PlayQueue {
     }
 
     @Override
-    public void load(int index, boolean loadNeighbors) {
+    public void load(int index) {
-        if (index > streams.size() || streams.get(index) == null) return;
+        if (index > getStreams().size() || getStreams().get(index) == null) return;
-
+        getStreams().get(index).load();
-        streams.get(index).load();
-
-        if (loadNeighbors) {
-            int leftBound = index - LOAD_BOUND >= 0 ? index - LOAD_BOUND : 0;
-            int rightBound = index + LOAD_BOUND < streams.size() ? index + LOAD_BOUND : streams.size() - 1;
-
-            for (int i = leftBound; i < rightBound; i++) {
-                final PlayQueueItem item = streams.get(i);
-                if (item != null) item.load();
-            }
-        }
     }
 
     @Override
-    public Maybe<StreamInfo> get(int index) {
+    public PlayQueueItem get(int index) {
-        if (index > streams.size() || streams.get(index) == null) return Maybe.empty();
+        if (index > getStreams().size() || getStreams().get(index) == null) return null;
-        return streams.get(index).getStream();
+        return getStreams().get(index);
     }
 
-
+    @Override
-    public synchronized void fetch() {
+    public void fetch() {
-        final int page = pageNumber.getAndIncrement();
+        if (fetchReactor != null && !fetchReactor.isDisposed()) return;
 
         final Callable<PlayListInfo> task = new Callable<PlayListInfo>() {
             @Override
             public PlayListInfo call() throws Exception {
-                PlayListExtractor extractor = service.getPlayListExtractorInstance(playlist.getLink(), page);
+                PlayListExtractor extractor = service.getPlayListExtractorInstance(playlistUrl, pageNumber.get());
                 return PlayListInfo.getInfo(extractor);
             }
         };
@@ -86,18 +76,23 @@ public class ExternalPlayQueue extends PlayQueue {
             public void accept(PlayListInfo playListInfo) throws Exception {
                 if (!playListInfo.hasNextPage) isComplete = true;
 
-                streams.addAll(extractPlaylistItems(playListInfo));
+                append(extractPlaylistItems(playListInfo));
-                notifyChange();
+                pageNumber.incrementAndGet();
             }
         };
 
-        Maybe.fromCallable(task)
+        fetchReactor = Maybe.fromCallable(task)
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .onErrorComplete()
                 .subscribe(onSuccess);
     }
 
+    @Override
+    public void dispose() {
+        if (fetchReactor != null) fetchReactor.dispose();
+    }
+
     private List<PlayQueueItem> extractPlaylistItems(final PlayListInfo info) {
         List<PlayQueueItem> result = new ArrayList<>();
         for (final InfoItem stream : info.related_streams) {
@@ -107,12 +102,4 @@ public class ExternalPlayQueue extends PlayQueue {
         }
         return result;
     }
-
-    private StreamingService getService(final int serviceId) {
-        try {
-            return NewPipe.getService(serviceId);
-        } catch (ExtractionException e) {
-            return null;
-        }
-    }
 }

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

@@ -2,41 +2,138 @@ package org.schabi.newpipe.playlist;
 
 import android.support.annotation.NonNull;
 
+import org.schabi.newpipe.extractor.NewPipe;
+import org.schabi.newpipe.extractor.StreamingService;
+import org.schabi.newpipe.extractor.exceptions.ExtractionException;
 import org.schabi.newpipe.extractor.stream_info.StreamInfo;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
 
+import io.reactivex.BackpressureStrategy;
+import io.reactivex.Flowable;
 import io.reactivex.Maybe;
 import io.reactivex.subjects.BehaviorSubject;
 
 public abstract class PlayQueue {
     private final String TAG = "PlayQueue@" + Integer.toHexString(hashCode());
 
-    final int LOAD_BOUND = 2;
+    private List<PlayQueueItem> streams;
+    private AtomicInteger queueIndex;
 
-    protected List<PlayQueueItem> streams;
+    private BehaviorSubject<PlayQueueEvent> changeBroadcast;
-    private BehaviorSubject<List<PlayQueueItem>> changeBroadcast;
+    private Flowable<PlayQueueEvent> playQueueFlowable;
 
-    PlayQueue() {
+    PlayQueue(final int index) {
         streams = Collections.synchronizedList(new ArrayList<PlayQueueItem>());
+        queueIndex = new AtomicInteger(index);
+
         changeBroadcast = BehaviorSubject.create();
+        playQueueFlowable = changeBroadcast.startWith(PlayQueueEvent.INIT).toFlowable(BackpressureStrategy.BUFFER);
+    }
+
+    // a queue is complete if it has loaded all items in an external playlist
+    // single stream or local queues are always complete
+    public abstract boolean isComplete();
+
+    // load in the background the item at index, may do nothing if the queue is incomplete
+    public abstract void load(int index);
+
+    // load partial queue in the background, does nothing if the queue is complete
+    public abstract void fetch();
+
+    // returns a Rx Future to the stream info of the play queue item at index
+    // may return an empty of the queue is incomplete
+    public abstract PlayQueueItem get(int index);
+
+    public abstract void dispose();
+
+    public int size() {
+        return streams.size();
     }
 
     @NonNull
     public List<PlayQueueItem> getStreams() {
-        return streams;
+        return Collections.unmodifiableList(streams);
     }
 
-    public void notifyChange() {
+    @NonNull
-        changeBroadcast.onNext(streams);
+    public Flowable<PlayQueueEvent> getPlayQueueFlowable() {
+        return playQueueFlowable;
     }
 
-    public abstract boolean isComplete();
+    private void broadcast(final PlayQueueEvent event) {
+        changeBroadcast.onNext(event);
+    }
 
-    public abstract void load(int index, boolean loadNeighbors);
+    public int getIndex() {
+        return queueIndex.get();
+    }
 
-    public abstract Maybe<StreamInfo> get(int index);
+    public void setIndex(final int index) {
+        queueIndex.set(index);
+        broadcast(PlayQueueEvent.SELECT);
+    }
+
+    public void incrementIndex() {
+        queueIndex.incrementAndGet();
+        broadcast(PlayQueueEvent.NEXT);
+    }
+
+    protected void append(final PlayQueueItem item) {
+        streams.add(item);
+        broadcast(PlayQueueEvent.APPEND);
+    }
+
+    protected void append(final Collection<PlayQueueItem> items) {
+        streams.addAll(items);
+        broadcast(PlayQueueEvent.APPEND);
+    }
+
+    public void remove(final int index) {
+        if (index < streams.size()) {
+            streams.remove(index);
+            broadcast(PlayQueueEvent.REMOVE);
+        }
+    }
+
+    protected void clear() {
+        if (!streams.isEmpty()) {
+            streams.clear();
+            broadcast(PlayQueueEvent.CLEAR);
+        }
+    }
+
+    protected void swap(final int source, final int target) {
+        final List<PlayQueueItem> items = streams;
+        if (source < items.size() && target < items.size()) {
+            // Swap two items
+            final PlayQueueItem sourceItem = items.get(source);
+            final PlayQueueItem targetItem = items.get(target);
+
+            items.set(target, sourceItem);
+            items.set(source, targetItem);
+
+            // If the current playing index is one of the swapped indices, change that as well
+            final int index = queueIndex.get();
+            if (index == source || index == target) {
+                final int newIndex = index == source ? target : source;
+                queueIndex.set(newIndex);
+            }
+
+            broadcast(PlayQueueEvent.SWAP);
+        }
+    }
+
+    protected StreamingService getService(final int serviceId) {
+        try {
+            return NewPipe.getService(serviceId);
+        } catch (ExtractionException e) {
+            return null;
+        }
+    }
 }
 

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

@@ -11,6 +11,9 @@ import org.schabi.newpipe.info_list.StreamInfoItemHolder;
 
 import java.util.List;
 
+import io.reactivex.disposables.Disposable;
+import io.reactivex.functions.Consumer;
+
 /**
  * Created by Christian Schabesberger on 01.08.16.
  *
@@ -34,12 +37,14 @@ import java.util.List;
 public class PlayQueueAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
     private static final String TAG = PlayQueueAdapter.class.toString();
 
-    private final PlaylistItemBuilder playlistItemBuilder;
+    private final PlayQueueItemBuilder playQueueItemBuilder;
     private final PlayQueue playQueue;
     private boolean showFooter = false;
     private View header = null;
     private View footer = null;
 
+    private Disposable playQueueReactor;
+
     public class HFHolder extends RecyclerView.ViewHolder {
         public HFHolder(View v) {
             super(v);
@@ -48,66 +53,57 @@ public class PlayQueueAdapter extends RecyclerView.Adapter<RecyclerView.ViewHold
         public View view;
     }
 
-    public void showFooter(boolean show) {
+    public void showFooter(final boolean show) {
         showFooter = show;
         notifyDataSetChanged();
     }
 
-    public PlayQueueAdapter(PlayQueue playQueue) {
+    public PlayQueueAdapter(final PlayQueue playQueue) {
-        this.playlistItemBuilder = new PlaylistItemBuilder();
+        this.playQueueItemBuilder = new PlayQueueItemBuilder();
         this.playQueue = playQueue;
+
+        playQueueReactor = getReactor();
     }
 
-    public void setSelectedListener(PlaylistItemBuilder.OnSelectedListener listener) {
+    public void setSelectedListener(final PlayQueueItemBuilder.OnSelectedListener listener) {
-        playlistItemBuilder.setOnSelectedListener(listener);
+        playQueueItemBuilder.setOnSelectedListener(listener);
     }
 
-    public void addItems(List<PlayQueueItem> data) {
+    public void add(final List<PlayQueueItem> data) {
-        if(data != null) {
+        playQueue.append(data);
-            playQueue.getStreams().addAll(data);
-            notifyPlaylistChange();
-        }
     }
 
-    public void addItem(PlayQueueItem data) {
+    public void add(final PlayQueueItem data) {
-        if (data != null) {
+        playQueue.append(data);
-            playQueue.getStreams().add(data);
-            notifyPlaylistChange();
-        }
     }
 
-    public void removeItem(int index) {
+    public void remove(final int index) {
-        if (index < playQueue.getStreams().size()) {
+        playQueue.remove(index);
-            playQueue.getStreams().remove(index);
-            notifyPlaylistChange();
-        }
     }
 
-    public void swapItems(int source, int target) {
+    public void swap(final int source, final int target) {
-        final List<PlayQueueItem> items = playQueue.getStreams();
+        playQueue.swap(source, target);
-        if (source < items.size() && target < items.size()) {
-            final PlayQueueItem sourceItem = items.get(source);
-            final PlayQueueItem targetItem = items.get(target);
-
-            items.set(target, sourceItem);
-            items.set(source, targetItem);
-
-            notifyPlaylistChange();
-        }
     }
 
     public void clear() {
-        if(playQueue.getStreams().isEmpty()) {
+        playQueue.clear();
-            return;
-        }
-        playQueue.getStreams().clear();
-
-        notifyPlaylistChange();
     }
 
-    private void notifyPlaylistChange() {
+    private Disposable getReactor() {
-        playQueue.notifyChange();
+        final Consumer<PlayQueueEvent> onNext = new Consumer<PlayQueueEvent>() {
-        notifyDataSetChanged();
+            @Override
+            public void accept(PlayQueueEvent playQueueEvent) throws Exception {
+                notifyDataSetChanged();
+            }
+        };
+
+        return playQueue.getPlayQueueFlowable()
+                .toObservable()
+                .subscribe(onNext);
+    }
+
+    public void dispose() {
+        if (playQueueReactor != null) playQueueReactor.dispose();
     }
 
     public void setHeader(View header) {
@@ -155,7 +151,7 @@ public class PlayQueueAdapter extends RecyclerView.Adapter<RecyclerView.ViewHold
                 return new HFHolder(footer);
             case 2:
                 return new StreamInfoItemHolder(LayoutInflater.from(parent.getContext())
-                        .inflate(R.layout.playlist_stream_item, parent, false));
+                        .inflate(R.layout.play_queue_item, parent, false));
             default:
                 Log.e(TAG, "Trollolo");
                 return null;
@@ -168,7 +164,7 @@ public class PlayQueueAdapter extends RecyclerView.Adapter<RecyclerView.ViewHold
             if(header != null) {
                 i--;
             }
-            playlistItemBuilder.buildStreamInfoItem((PlayQueueItemHolder) holder, playQueue.getStreams().get(i));
+            playQueueItemBuilder.buildStreamInfoItem((PlayQueueItemHolder) holder, playQueue.getStreams().get(i));
         } else if(holder instanceof HFHolder && i == 0 && header != null) {
             ((HFHolder) holder).view = header;
         } else if(holder instanceof HFHolder && i == playQueue.getStreams().size() && footer != null && showFooter) {

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

@@ -0,0 +1,27 @@
+package org.schabi.newpipe.playlist;
+
+public enum PlayQueueEvent {
+    INIT,
+
+    // sent when the user is seamlessly transitioned by exoplayer to the next stream
+    NEXT,
+
+    // sent when the user transitions to an unbuffered period
+    SELECT,
+
+    // sent when more streams are added to the play queue
+    APPEND,
+
+    // sent when a pending stream is removed from the play queue
+    REMOVE,
+
+    // sent when the current stream is removed
+    REMOVE_CURRENT,
+
+    // sent when two streams swap place in the play queue
+    SWAP,
+
+    // sent when streams is cleared
+    CLEAR
+}
+

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

@@ -8,7 +8,6 @@ import org.schabi.newpipe.extractor.stream_info.StreamExtractor;
 import org.schabi.newpipe.extractor.stream_info.StreamInfo;
 import org.schabi.newpipe.extractor.stream_info.StreamInfoItem;
 
-import java.io.Serializable;
 import java.util.concurrent.Callable;
 
 import io.reactivex.Maybe;
@@ -17,7 +16,7 @@ import io.reactivex.functions.Action;
 import io.reactivex.functions.Consumer;
 import io.reactivex.schedulers.Schedulers;
 
-public class PlayQueueItem implements Serializable {
+public class PlayQueueItem {
 
     private String title;
     private String url;

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

@@ -10,9 +10,9 @@ import org.schabi.newpipe.R;
 import java.util.Locale;
 
 
-public class PlaylistItemBuilder {
+public class PlayQueueItemBuilder {
 
-    private static final String TAG = PlaylistItemBuilder.class.toString();
+    private static final String TAG = PlayQueueItemBuilder.class.toString();
 
     public interface OnSelectedListener {
         void selected(int serviceId, String url, String title);
@@ -20,7 +20,7 @@ public class PlaylistItemBuilder {
 
     private OnSelectedListener onStreamInfoItemSelectedListener;
 
-    public PlaylistItemBuilder() {}
+    public PlayQueueItemBuilder() {}
 
     public void setOnSelectedListener(OnSelectedListener listener) {
         this.onStreamInfoItemSelectedListener = listener;
@@ -28,7 +28,7 @@ public class PlaylistItemBuilder {
 
     public View buildView(ViewGroup parent, final PlayQueueItem item) {
         final LayoutInflater inflater = LayoutInflater.from(parent.getContext());
-        final View itemView = inflater.inflate(R.layout.stream_item, parent, false);
+        final View itemView = inflater.inflate(R.layout.play_queue_item, parent, false);
         final PlayQueueItemHolder holder = new PlayQueueItemHolder(itemView);
 
         buildStreamInfoItem(holder, item);