Dart 产生来自另一个流监听器的流事件

我有一个函数可以生成stream的具体事件。现在我有一个来自存储服务的流，它有自己的事件。寻找一种方法在发生变化时产生我的事件storage stream.

这段代码片段并不能解决问题。

Stream<BlocState> mapEventToState(
    BlocEvent event,
  ) async* {
  if (event is UploadData) {
    yield UploadDataProgress(progress: 0.0);
    final Storage storage = Storage();
    final Stream<StorageEvent> upload = storage.upload(event.data);

    upload.listen((StorageEvent storageEvent) async* {
      print('***** Listener: ${storageEvent.type} - ${storageEvent.progress}');

      if (storageEvent.type == StorageEventType.error) {
        yield UploadDataError(errorMessage: storageEvent.error);
      }

      if (storageEvent.type == StorageEventType.success) {
        yield UploadDataSuccess();
      }

      if (storageEvent.type == StorageEventType.progress) {
        yield UploadDataProgress(progress: storageEvent.progress);
      }
    });
  }
}

输出： 调试打印可以工作，但事件不会发送到侦听器。

***** Listener: StorageEventType.progress - 0.01924033836457124
***** Listener: StorageEventType.progress - 0.044581091468101464
***** Listener: StorageEventType.progress - 0.6986233206170177
***** Listener: StorageEventType.progress - 1.0

Your yields 从匿名函数中产生(StorageEvent storageEvent) async* {而不是来自mapEventToState.

只需更换listen()与await for应该管用。

Stream<BlocState> mapEventToState(
    BlocEvent event,
  ) async* {
  if (event is UploadData) {
    yield UploadDataProgress(progress: 0.0);
    final Storage storage = Storage();
    final Stream<StorageEvent> upload = storage.upload(event.data);

    await for (StorageEvent storageEvent in upload) {
      print('***** Listener: ${storageEvent.type} - ${storageEvent.progress}');

      if (storageEvent.type == StorageEventType.error) {
        yield UploadDataError(errorMessage: storageEvent.error);
      }

      if (storageEvent.type == StorageEventType.success) {
        yield UploadDataSuccess();
      }

      if (storageEvent.type == StorageEventType.progress) {
        yield UploadDataProgress(progress: storageEvent.progress);
      }
    }
  }
}