Flutter：将两个流串流到一个屏幕中？ [英] Flutter : stream two Streams into a single screen?

问题描述

我有两个从两个不同的api获取的流。

I have two streams fetching from two different api.

Stream<Month> get monthOutStream => monthOutController.stream;
Stream<MySchedule> get resultOutStream => resultController.stream;

我正在应用程序的两种不同状态下获取这些数据，这些结果在开始时和几个月后

I am fetching these data at two different state of the application, result at the begining and Months after some events from user.

MyScheduleBloc(){
  initialData();
}

Future initialData() async {
  MySchedule mySchedule = await myScheduleViewModel.importMySchedule(now.id);
  resultController.add(mySchedule);
}

我的屏幕上有一个流生成器，

My screen has a streambuilder as

Widget build(BuildContext context) {
final webCalenderBloc = WebCalenderBloc();
return StreamBuilder(
  stream: webCalenderBloc.resultOutStream,
  builder: (BuildContext context , snapdata){
    if(!snapdata.hasData){
      return Center(
        child: CircularProgressIndicator(),
      );
    }
    return body(snapdata.data);
   },
 );
}

由于主窗口小部件构建方法将StreamBuilder窗口小部件与resultoutstream作为流。我在哪里获取其他流monthoutStream。
我可以在流中获取流吗？我在处理两个流时是否缺少任何内容。我不想从monthoutstream构建任何小部件，但希望检查其中的数据。

Since the main widget build method took the StreamBuilder Widget with resultoutstream as a stream.Where do i fetch the other stream monthoutStream. Can i fetch stream inside a stream? Do i missing anything while handling two stream.I dont want to build any widget from monthoutstream but want to check the data inside it.

推荐答案

如果需要，您可以嵌套 StreamBuilder 。没有什么可以阻止您执行以下操作：

You can nest StreamBuilder if needed. Nothing prevents you from doing the following:

StreamBuilder(
  stream: stream1,
  builder: (context, snapshot1) {
    return StreamBuilder(
      stream: stream2,
      builder: (context, snapshot2) {
        // do some stuff with both streams here
      },
    );
  },
)

另一个解决方案对您而言有意义的是：流被设计为可合并/转换的。您可以创建第三个流，该流是后面两个流的合并。

Another solution if this makes sense for you is: Streams are designed to be mergeable/transformed. You could make a third stream that is a merge of the two later streams.

理想情况下，对于复杂的流操作，您将要使用 rxdart ，因为它提供了一些有用的转换器。

Ideally for complex stream operations you'll want to use rxdart as it provides a few useful transformer.

使用rxdart，将两个 Observable （其中是 Stream 的子类）

Using rxdart, the fusion of two Observable (which are subclass of Stream) would be the following:

Observable<bool> stream1;
Observable<String> stream2;

final fusion = stream1.withLatestFrom(stream2, (foo, bar) {
  return MyClass(foo: foo, bar: bar);
});

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