Rebuild VideoPlayer once VideoPlayerController finishes initialization. (#767)

* Rebuild VideoPlayer once VideoPlayerController finishes initialization.

Otherwise if VideoPlayer is built shortly after the controller starts initialization and doesn't yet have _textureId filled the widgets renders as an empty Container and never rebuilds to show the video later.

* Queue VideoPlayer events in the EventSink.

This ensure that initialization events that are generated in `onPlayerStateChanged` before the Dart side has chance to subscribe to the channel are queued and eventually delivered.

Fixes flutter/flutter#21483.

Author: nichtverstehen

packages/video_player/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.6.5
+
+* Eliminate race conditions around initialization: now initialization events are queued and guaranteed
+  to be delivered to the Dart side. VideoPlayer widget is rebuilt upon completion of initialization.
+
 ## 0.6.4
 
 * Android: add support for hls, dash and ss video formats.

packages/video_player/android/src/main/java/io/flutter/plugins/videoplayer/QueuingEventSink.java

@@ -0,0 +1,81 @@
+package io.flutter.plugins.videoplayer;
+
+import io.flutter.plugin.common.EventChannel;
+import java.util.ArrayList;
+
+/**
+ * And implementation of {@link EventChannel.EventSink} which can wrap an underlying sink.
+ *
+ * <p>It delivers messages immediately when downstream is available, but it queues messages before
+ * the delegate event sink is set with setDelegate.
+ *
+ * <p>This class is not thread-safe. All calls must be done on the same thread or synchronized
+ * externally.
+ */
+final class QueuingEventSink implements EventChannel.EventSink {
+  private EventChannel.EventSink delegate;
+  private ArrayList<Object> eventQueue = new ArrayList<>();
+  private boolean done = false;
+
+  public void setDelegate(EventChannel.EventSink delegate) {
+    this.delegate = delegate;
+    maybeFlush();
+  }
+
+  @Override
+  public void endOfStream() {
+    enqueue(new EndOfStreamEvent());
+    maybeFlush();
+    done = true;
+  }
+
+  @Override
+  public void error(String code, String message, Object details) {
+    enqueue(new ErrorEvent(code, message, details));
+    maybeFlush();
+  }
+
+  @Override
+  public void success(Object event) {
+    enqueue(event);
+    maybeFlush();
+  }
+
+  private void enqueue(Object event) {
+    if (done) {
+      return;
+    }
+    eventQueue.add(event);
+  }
+
+  private void maybeFlush() {
+    if (delegate == null) {
+      return;
+    }
+    for (Object event : eventQueue) {
+      if (event instanceof EndOfStreamEvent) {
+        delegate.endOfStream();
+      } else if (event instanceof ErrorEvent) {
+        ErrorEvent errorEvent = (ErrorEvent) event;
+        delegate.error(errorEvent.code, errorEvent.message, errorEvent.details);
+      } else {
+        delegate.success(event);
+      }
+    }
+    eventQueue.clear();
+  }
+
+  private static class EndOfStreamEvent {}
+
+  private static class ErrorEvent {
+    String code;
+    String message;
+    Object details;
+
+    ErrorEvent(String code, String message, Object details) {
+      this.code = code;
+      this.message = message;
+      this.details = details;
+    }
+  }
+}

packages/video_player/android/src/main/java/io/flutter/plugins/videoplayer/VideoPlayerPlugin.java

@@ -59,7 +59,7 @@ private static class VideoPlayer {
 
     private final TextureRegistry.SurfaceTextureEntry textureEntry;
 
-    private EventChannel.EventSink eventSink;
+    private QueuingEventSink eventSink = new QueuingEventSink();
 
     private final EventChannel eventChannel;
 
@@ -128,12 +128,12 @@ private void setupVideoPlayer(
           new EventChannel.StreamHandler() {
             @Override
             public void onListen(Object o, EventChannel.EventSink sink) {
-              eventSink = sink;
+              eventSink.setDelegate(sink);
             }
 
             @Override
             public void onCancel(Object o) {
-              eventSink = null;
+              eventSink.setDelegate(null);
             }
           });
 
@@ -148,14 +148,12 @@ public void onCancel(Object o) {
             public void onPlayerStateChanged(final boolean playWhenReady, final int playbackState) {
               super.onPlayerStateChanged(playWhenReady, playbackState);
               if (playbackState == Player.STATE_BUFFERING) {
-                if (eventSink != null) {
-                  Map<String, Object> event = new HashMap<>();
-                  event.put("event", "bufferingUpdate");
-                  List<Integer> range = Arrays.asList(0, exoPlayer.getBufferedPercentage());
-                  // iOS supports a list of buffered ranges, so here is a list with a single range.
-                  event.put("values", Collections.singletonList(range));
-                  eventSink.success(event);
-                }
+                Map<String, Object> event = new HashMap<>();
+                event.put("event", "bufferingUpdate");
+                List<Integer> range = Arrays.asList(0, exoPlayer.getBufferedPercentage());
+                // iOS supports a list of buffered ranges, so here is a list with a single range.
+                event.put("values", Collections.singletonList(range));
+                eventSink.success(event);
               } else if (playbackState == Player.STATE_READY && !isInitialized) {
                 isInitialized = true;
                 sendInitialized();
@@ -212,7 +210,7 @@ long getPosition() {
     }
 
     private void sendInitialized() {
-      if (isInitialized && eventSink != null) {
+      if (isInitialized) {
         Map<String, Object> event = new HashMap<>();
         event.put("event", "initialized");
         event.put("duration", exoPlayer.getDuration());

packages/video_player/lib/video_player.dart

@@ -420,16 +420,39 @@ class _VideoAppLifeCycleObserver extends WidgetsBindingObserver {
 }
 
 /// Displays the video controlled by [controller].
-class VideoPlayer extends StatelessWidget {
+class VideoPlayer extends StatefulWidget {
   final VideoPlayerController controller;
 
   VideoPlayer(this.controller);
 
+  @override
+  _VideoPlayerState createState() => new _VideoPlayerState();
+}
+
+class _VideoPlayerState extends State<VideoPlayer> {
+  int textureId;
+
+  @override
+  void initState() {
+    super.initState();
+    textureId = widget.controller._textureId;
+    // Need to listen for initialization events since the actual texture ID
+    // becomes available after asynchronous initialization finishes.
+    widget.controller.addListener(() {
+      final int newTextureId = widget.controller._textureId;
+      if (newTextureId != textureId) {
+        setState(() {
+          textureId = newTextureId;
+        });
+      }
+    });
+  }
+
   @override
   Widget build(BuildContext context) {
-    return controller._textureId == null
+    return textureId == null
         ? new Container()
-        : new Texture(textureId: controller._textureId);
+        : new Texture(textureId: textureId);
   }
 }
 

packages/video_player/pubspec.yaml

@@ -2,7 +2,7 @@ name: video_player
 description: Flutter plugin for displaying inline video with other Flutter
   widgets on Android and iOS.
 author: Flutter Team <flutter-dev@googlegroups.com>
-version: 0.6.4
+version: 0.6.5
 homepage: https://github.com/flutter/plugins/tree/master/packages/video_player
 
 flutter: