Unhandled Exception: Bad state: Cannot add event after closing

[andrews-k]

fvp: ^0.37.3 android
_StreamController.add still throws an error in MdkVideoPlayer.

Problem 39 has been resolved, but some issues still arise.

[serious198706]

Also happens to me, here's the log.

I/flutter (18681): Bad state: Cannot add event after closing
I/flutter (18681): #0      _StreamController.add (dart:async/stream_controller.dart:617:24)
stream_controller.dart:617
I/flutter (18681): #1      new MdkVideoPlayer.<anonymous closure> (package:fvp/src/video_player_mdk.dart:93:19)
video_player_mdk.dart:93
I/flutter (18681): #2      _RootZone.runUnaryGuarded (dart:async/zone.dart:891:10)
zone.dart:891
I/flutter (18681): #3      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:381:11)
stream_impl.dart:381
I/flutter (18681): #4      _DelayedData.perform (dart:async/stream_impl.dart:573:14)
stream_impl.dart:573
I/flutter (18681): #5      _PendingEvents.handleNext (dart:async/stream_impl.dart:678:11)
stream_impl.dart:678
I/flutter (18681): #6      _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:649:7)
stream_impl.dart:649
I/flutter (18681): #7      _microtaskLoop (dart:async/schedule_microtask.dart:40:35)
schedule_microtask.dart:40
I/flutter (18681): #8      _startMicrotaskLoop (dart:async/schedule_microtask.dart:49:5)
schedule_microtask.dart:49

[serious198706]

1. 页面切换时，VideoPlayer 被销毁
2. VideoPlayerController.dispose() 会关闭 streamCtl
3. 但 MDK 原生层仍可能异步发送 reader.buffering 事件
4. 调尝试 streamCtl.add(...) → Bad state: Cannot add event after closing

[wang-bin]

Root cause

This issue is caused by a lifecycle race during player disposal.

Before the fix:

1. MdkVideoPlayer.dispose() closed streamCtl immediately.
2. The native media/status/state subscriptions were still active.
3. The original dispose() method returned void, so the platform layer could not await native cleanup.
4. Delayed callbacks from textureSize, buffering, playback state, stopped events, and error paths could still call add() or addError() after the stream had been closed.

sequenceDiagram
    participant App as Flutter Controller
    participant Mdk as MdkVideoPlayer
    participant Stream as streamCtl
    participant Native as Native/MDK callbacks

    App->>Mdk: dispose()
    Mdk->>Stream: close()
    Note over Mdk,Native: Native cleanup is still pending
    Native-->>Mdk: media status / buffering / stopped
    Mdk->>Stream: add(VideoEvent)
    Stream-->>Mdk: StateError

Loading

Fix

The lifecycle handling has been updated in commit 09a6e15:

• Added an idempotent Future<void> disposeAsync() API.
• Kept the existing dispose() API unchanged; it now starts disposeAsync() with unawaited(...).
• Marked the player as disposed before the first asynchronous operation.
• Stored and cancelled the media status, event, and playback state subscriptions.
• Routed all event/error writes through disposed/closed checks.
• Changed platform disposal to await player.disposeAsync().
• Added protection for pending textureSize cleanup so disposal does not wait indefinitely for a video size.
• Enforced the cleanup order:

flowchart TD
    A[dispose / disposeAsync] --> B[Mark player disposed]
    B --> C[Cancel native event subscriptions]
    C --> D[Release texture]
    D --> E[Stop player]
    E --> F[Unregister native callbacks]
    F --> G[Close Dart streams]
    G --> H[Close ReceivePort]
    H --> I[Delete native player]
    I --> J[Close MdkVideoPlayer streamCtl]

Loading

Existing callers can continue using player.dispose() without any changes. Callers that need to wait for cleanup can use await player.disposeAsync().

Regression coverage

Added an Android integration test covering:

• Disposing while initialization is still pending.
• Repeated dispose/recreate cycles.
• Disposal after playback.
• Pending media status, buffering, stopped, and error callbacks.
• Assertion that no Cannot add event after closing error is emitted.

The affected source files and the integration test pass static analysis. Full Android execution was blocked locally before reaching the test code by the existing Gradle plugin-loader/cache issue in the example project.

[wang-bin]

try 09a6e15