Flutter:将两个 Streams 流式传输到一个屏幕中? [英] Flutter : stream two Streams into a single screen?

问题描述

我有两个流从两个不同的 api 中获取.

I have two streams fetching from two different api.

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

我在应用程序的两个不同状态下获取这些数据，结果是在用户发生某些事件的开始和几个月之后.

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);
   },
 );
}

由于主要的小部件构建方法将带有 resultoutstream 的 StreamBuilder 小部件作为流.我在哪里获取其他流monthoutStream.我可以在流中获取流吗?处理两个流时我是否遗漏了什么.我不想从monthoutstream 构建任何小部件，但想检查其中的数据.

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
      },
    );
  },
)

如果这对您有意义，另一个解决方案是:流被设计为可合并/转换.您可以创建第三个流，该流是后两个流的合并.

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.

对于复杂的流操作，您最好使用 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，两个Observable(Stream的子类)的融合如下:

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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