[video_player] Move Android buffer updates to Dart #9771

stuartmorgan-g · 2025-08-07T17:37:56Z

Since ExoPlayer does not generate events for changes to the buffer position, the video_player_android synthesizes them via polling. This moves the logic to generate these events from Java to Dart, to reduce the amount of logic on the Java side.

This does not attempt to fix the structural problem that the workaround was piggy-backed on the fact that the app-facing package polls frequently for the playback position, generating buffer update events when that polling happens rather than via any independent internal polling system. This approach is not only fragile, as it depends on logic defined in another package, but already doesn't work in the case of a paused video. However, this refactoring will make it possible to change this behavior in Dart code in a follow-up focused on that behavioral change. This change should be behavior-neutral, except that it adds the simple improvement of not creating events if the buffer position hasn't changed, so that clients aren't getting a stream of useless buffer position events during playback.

This version will also be more efficient from a platform channel standpoint, since instead of sending a separate message with the buffer position, it's returned in the same call as the playback position.

To support synthesizing events on the Dart side, this adds a custom stream controller in Dart, instead of creating it directly from the EventChannel stream; this change will make future changes to a non-method-channel approach (e.g., FFI callbacks) straightforward. As this adds non-trivial additional per-player-instance state on the Dart side, this adds a Dart player instance class, and consolidates existing state into that class, including passthrough methods for the API calls, making it clearer which state is plugin level vs player level.

Part of flutter/flutter#172763

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Code Review

This pull request is a nice refactoring that moves the buffer update logic from the native Android side to Dart. This simplifies the native code and improves efficiency by bundling playback and buffer position updates into a single platform channel call. The introduction of the _PlayerInstance class is a great structural improvement for managing per-player state in Dart.

I have a couple of suggestions for minor improvements: one to align a test method name with Java conventions, and another to remove what appears to be dead code following the refactoring. Overall, this is a solid change.

gemini-code-assist · 2025-08-07T17:38:58Z

packages/video_player/video_player_android/lib/src/android_video_player.dart

+      'bufferingUpdate' => VideoEvent(
+        eventType: VideoEventType.bufferingUpdate,
+        buffered: _bufferRangeForPosition(map['position'] as int),
+      ),


This bufferingUpdate case appears to be unreachable. With the refactoring in this PR, the logic for sending buffer updates has been moved from the native Java code to the getPosition method in Dart. The native side should no longer be sending 'bufferingUpdate' events, making this case dead code. It can be safely removed.

This is not correct; the Java code still sends this when the player enters STATE_BUFFERING.

...deo_player_android/android/src/test/java/io/flutter/plugins/videoplayer/VideoPlayerTest.java

stuartmorgan-g · 2025-08-07T17:38:33Z

packages/video_player/video_player_android/lib/src/android_video_player.dart

-        ),
-        _ => VideoEvent(eventType: VideoEventType.unknown),
-      };
-    });


This switch is moved almost unchanged to the player instance class below.

stuartmorgan-g · 2025-08-07T17:39:09Z

packages/video_player/video_player_android/lib/src/android_video_player.dart

+
+  // Turns a single buffer position, which is what ExoPlayer reports, into the
+  // DurationRange array expected by [VideoEventType.bufferingUpdate].
+  List<DurationRange> _bufferRangeForPosition(int milliseconds) {


This was extracted from the switch to allow it to be used in _updateBufferingState as well.

stuartmorgan-g · 2025-08-07T17:40:27Z

packages/video_player/video_player_android/lib/src/android_video_player.dart

+    //  that the app-facing package polls getPosition frequently, which makes
+    //  this fragile (for instance, as of writing, this won't be called while
+    //  the video is paused). It should instead be called on its own timer,
+    //  independent of higher-level package logic.


I've expanded on the explanation relative to the version removed from VideoPlayer.java, but it's still fundamentally the same hack as the Java version was for now (to minimize behavioral changes in this PR).

ash2moon · 2025-08-14T18:20:58Z

packages/video_player/video_player_android/pigeons/messages.dart

@@ -50,7 +60,12 @@ abstract class VideoPlayerInstanceApi {
  void setVolume(double volume);
  void setPlaybackSpeed(double speed);
  void play();
-  int getPosition();
  void seekTo(int position);


Can we specify that the position is also in milliseconds here?

Good call; added docs to all of these methods.

ash2moon · 2025-08-14T18:22:07Z

packages/video_player/video_player_android/pigeons/messages.dart

  void setVolume(double volume);
  void setPlaybackSpeed(double speed);


I think it might help to provide what that max/min bounds of these values would be or at least specify the unit.

ash2moon · 2025-08-14T18:22:51Z

packages/video_player/video_player_android/lib/src/android_video_player.dart

+        VideoViewType.platformView => const _VideoPlayerPlatformViewState(),
+      };
+      final String eventChannelName =
+          'flutter.io/videoPlayer/videoEvents$playerId';


Can we make the magic string a constant outside of this method?

Extracted, and added a comment about the value it has to match on the other side.

…/packages#9771)

flutter/packages@09533b7...5c52c55 2025-08-15 [email protected] [video_player] Move Android buffer updates to Dart (flutter/packages#9771) 2025-08-15 [email protected] [webview_flutter] Add support for payment requests on Android (flutter/packages#9679) 2025-08-15 [email protected] [vector_graphics_compiler] Set the m4_10 (Z scale) value to 1 when constructing an AffineMatrix from an SVG matrix (flutter/packages#9813) 2025-08-15 [email protected] [url_launcher_ios] Fix test button text to work on iOS 26 (flutter/packages#9766) 2025-08-15 [email protected] [video_player] Simplify native iOS code (flutter/packages#9800) 2025-08-14 [email protected] [image_picker] Add the ability to pick multiple videos - platform_interface (flutter/packages#9804) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages-flutter-autoroll Please CC [email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

stuartmorgan-g added 6 commits August 6, 2025 14:23

Add player class as an initial abstraction

5b227a4

Fold view state into the instance

fa87a01

Move event stream to the instance class

2f3a4df

Move buffer update event synthesis to Dart

1f88457

Version bump

fc1cd2a

Remove unused method

395b7ba

stuartmorgan-g requested a review from ash2moon as a code owner August 7, 2025 17:37

github-actions bot added platform-android p: video_player labels Aug 7, 2025

gemini-code-assist bot reviewed Aug 7, 2025

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stuartmorgan-g commented Aug 7, 2025

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stuartmorgan-g added 3 commits August 7, 2025 13:46

Fix capitalization

796ab14

Switch to a non-broadcast stream to keep queue behavior

93f36e3

Merge branch 'main' into video-player-move-buffering-workaround

6d5e1a9

reidbaker mentioned this pull request Aug 14, 2025

The video player value.isBuffering returns true as soon as a video finishes playing on android flutter/flutter#170737

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ash2moon approved these changes Aug 14, 2025

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stuartmorgan-g added the autosubmit Merge PR when tree becomes green via auto submit App label Aug 15, 2025

auto-submit bot merged commit 5c52c55 into flutter:main Aug 15, 2025
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engine-flutter-autoroll added a commit to engine-flutter-autoroll/flutter that referenced this pull request Aug 15, 2025

5c52c5545 [video_player] Move Android buffer updates to Dart (flutter…

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…/packages#9771)

engine-flutter-autoroll mentioned this pull request Aug 15, 2025

Roll Packages from 09533b7d5d66 to 5c52c5545f54 (6 revisions) flutter/flutter#173854

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		void setVolume(double volume);
		void setPlaybackSpeed(double speed);

[video_player] Move Android buffer updates to Dart #9771

[video_player] Move Android buffer updates to Dart #9771

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stuartmorgan-g commented Aug 7, 2025

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