flutter实现promise中resolve(RxJava中emiter.onSucess("result"))功能

BehaviorSubject openCameraController = BehaviorSubject();

BridgeChannel _openCamera() {
    print('- - - - - - - - - - - - - - - - - - > _openCamera() ');
    return BridgeChannel(
        name: 'openCamera',
        onBridgeHandler: (dataFromJs) async {
            print('- - - - - - - - - - - - - - - - - - > 111 '+dataFromJs);
            EventBus().post(OpenCameraEvent(dataFromJs));
            print('- - - - - - - - - - - - - - - - - -> 222 ');
            String str = await doSome();
            print(" - - - - - - - - - - - - - - - - - - > 555 "+str);
            return str;
        }
    );
}

Future<String> doSome() async {
　　// 注意Future的范型不正确的话，await Future完不会生成String
    Future<String> future = new Future(() => "");
    openCameraController.listen((resul) async {
        future.then((_) => resul);
    });
    return future;
}