-Refactored synchronization checks out from MediaSourceManager to ManagedMediaSource.

-Fixed null input causing potential NPE on PlayQueueItem.

app/src/main/java/org/schabi/newpipe/player/mediasource/FailedMediaSource.java

@@ -72,7 +72,13 @@ public class FailedMediaSource implements ManagedMediaSource {
     public void releaseSource() {}
 
     @Override
-    public boolean canReplace(@NonNull final PlayQueueItem newIdentity) {
+    public boolean shouldBeReplacedWith(@NonNull final PlayQueueItem newIdentity,
+                                        final boolean isInterruptable) {
         return newIdentity != playQueueItem || canRetry();
     }
+
+    @Override
+    public boolean isStreamEqual(@NonNull PlayQueueItem stream) {
+        return playQueueItem == stream;
+    }
 }

app/src/main/java/org/schabi/newpipe/player/mediasource/LoadedMediaSource.java

@@ -59,7 +59,13 @@ public class LoadedMediaSource implements ManagedMediaSource {
     }
 
     @Override
-    public boolean canReplace(@NonNull final PlayQueueItem newIdentity) {
+    public boolean shouldBeReplacedWith(@NonNull PlayQueueItem newIdentity,
-        return newIdentity != stream || isExpired();
+                                        final boolean isInterruptable) {
+        return newIdentity != stream || (isInterruptable && isExpired());
+    }
+
+    @Override
+    public boolean isStreamEqual(@NonNull PlayQueueItem stream) {
+        return this.stream == stream;
     }
 }

app/src/main/java/org/schabi/newpipe/player/mediasource/ManagedMediaSource.java

@@ -7,5 +7,21 @@ import com.google.android.exoplayer2.source.MediaSource;
 import org.schabi.newpipe.playlist.PlayQueueItem;
 
 public interface ManagedMediaSource extends MediaSource {
-    boolean canReplace(@NonNull final PlayQueueItem newIdentity);
+    /**
+     * Determines whether or not this {@link ManagedMediaSource} can be replaced.
+     *
+     * @param newIdentity a stream the {@link ManagedMediaSource} should encapsulate over, if
+     *                    it is different from the existing stream in the
+     *                    {@link ManagedMediaSource}, then it should be replaced.
+     * @param isInterruptable specifies if this {@link ManagedMediaSource} potentially
+     *                        being played.
+     * */
+    boolean shouldBeReplacedWith(@NonNull final PlayQueueItem newIdentity,
+                                 final boolean isInterruptable);
+
+    /**
+     * Determines if the {@link PlayQueueItem} is the one the
+     * {@link ManagedMediaSource} encapsulates over.
+     * */
+    boolean isStreamEqual(@NonNull final PlayQueueItem stream);
 }

app/src/main/java/org/schabi/newpipe/player/mediasource/PlaceholderMediaSource.java

@@ -19,7 +19,13 @@ public class PlaceholderMediaSource implements ManagedMediaSource {
     @Override public void releaseSource() {}
 
     @Override
-    public boolean canReplace(@NonNull final PlayQueueItem newIdentity) {
+    public boolean shouldBeReplacedWith(@NonNull PlayQueueItem newIdentity,
+                                        final boolean isInterruptable) {
         return true;
     }
+
+    @Override
+    public boolean isStreamEqual(@NonNull PlayQueueItem stream) {
+        return false;
+    }
 }

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

@@ -268,15 +268,10 @@ public class MediaSourceManager {
     private boolean isPlaybackReady() {
         if (sources.getSize() != playQueue.size()) return false;
 
-        final MediaSource mediaSource = sources.getMediaSource(playQueue.getIndex());
+        final ManagedMediaSource mediaSource =
+                (ManagedMediaSource) sources.getMediaSource(playQueue.getIndex());
         final PlayQueueItem playQueueItem = playQueue.getItem();
-
+        return mediaSource.isStreamEqual(playQueueItem);
-        if (mediaSource instanceof LoadedMediaSource) {
-            return playQueueItem == ((LoadedMediaSource) mediaSource).getStream();
-        } else if (mediaSource instanceof FailedMediaSource) {
-            return playQueueItem == ((FailedMediaSource) mediaSource).getStream();
-        }
-        return false;
     }
 
     private void maybeBlock() {
@@ -453,12 +448,8 @@ public class MediaSourceManager {
         if (index == -1 || index >= sources.getSize()) return false;
 
         final ManagedMediaSource mediaSource = (ManagedMediaSource) sources.getMediaSource(index);
-
+        return mediaSource.shouldBeReplacedWith(item,
-        if (index == playQueue.getIndex() && mediaSource instanceof LoadedMediaSource) {
+                /*mightBeInProgress=*/index != playQueue.getIndex());
-            return item != ((LoadedMediaSource) mediaSource).getStream();
-        } else {
-            return mediaSource.canReplace(item);
-        }
     }
 
     /**
@@ -479,7 +470,7 @@ public class MediaSourceManager {
         final ManagedMediaSource currentSource =
                 (ManagedMediaSource) sources.getMediaSource(currentIndex);
         final PlayQueueItem currentItem = playQueue.getItem();
-        if (!currentSource.canReplace(currentItem)) {
+        if (!currentSource.shouldBeReplacedWith(currentItem, /*canInterruptOnRenew=*/true)) {
             maybeSynchronizePlayer();
             return;
         }

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

@@ -11,20 +11,19 @@ import org.schabi.newpipe.util.ExtractorHelper;
 import java.io.Serializable;
 
 import io.reactivex.Single;
-import io.reactivex.android.schedulers.AndroidSchedulers;
-import io.reactivex.functions.Consumer;
 import io.reactivex.schedulers.Schedulers;
 
 public class PlayQueueItem implements Serializable {
-    final public static long RECOVERY_UNSET = Long.MIN_VALUE;
+    public final static long RECOVERY_UNSET = Long.MIN_VALUE;
+    private final static String EMPTY_STRING = "";
 
-    final private String title;
+    @NonNull final private String title;
-    final private String url;
+    @NonNull final private String url;
     final private int serviceId;
     final private long duration;
-    final private String thumbnailUrl;
+    @NonNull final private String thumbnailUrl;
-    final private String uploader;
+    @NonNull final private String uploader;
-    final private StreamType streamType;
+    @NonNull final private StreamType streamType;
 
     private long recoveryPosition;
     private Throwable error;
@@ -42,15 +41,16 @@ public class PlayQueueItem implements Serializable {
                 item.getThumbnailUrl(), item.getUploaderName(), item.getStreamType());
     }
 
-    private PlayQueueItem(final String name, final String url, final int serviceId,
+    private PlayQueueItem(@Nullable final String name, @Nullable final String url,
-                          final long duration, final String thumbnailUrl, final String uploader,
+                          final int serviceId, final long duration,
-                          final StreamType streamType) {
+                          @Nullable final String thumbnailUrl, @Nullable final String uploader,
-        this.title = name;
+                          @NonNull final StreamType streamType) {
-        this.url = url;
+        this.title = name != null ? name : EMPTY_STRING;
+        this.url = url != null ? url : EMPTY_STRING;
         this.serviceId = serviceId;
         this.duration = duration;
-        this.thumbnailUrl = thumbnailUrl;
+        this.thumbnailUrl = thumbnailUrl != null ? thumbnailUrl : EMPTY_STRING;
-        this.uploader = uploader;
+        this.uploader = uploader != null ? uploader : EMPTY_STRING;
         this.streamType = streamType;
 
         this.recoveryPosition = RECOVERY_UNSET;
@@ -84,6 +84,7 @@ public class PlayQueueItem implements Serializable {
         return uploader;
     }
 
+    @NonNull
     public StreamType getStreamType() {
         return streamType;
     }