flutter - Flutter:结合多个Future 任务

Question

如何合并多个FutureTask，以便我们可以在同一响应中获得所有回调。
我们像这样使用Future<T>

Future<String> getData(int duration) async {
  await Future.delayed(Duration(seconds: duration)); //Mock delay
  return "This a test data for duration $duration";
}

调用上述方法，如 getData(2).then((value) => print(value));如果我们要调用多个“ future 任务”，我们该怎么做？

Answer 1

为此，FutureGroup可用于合并多个流

FutureGroup provides us the functionality of combining multiplefutures into one single group, which will give the callback at the endwhen all future tasks work gets completed.

依赖项:

dependencies:
  async: ^2.4.1

如何实现FutureGroup？

FutureGroup futureGroup = FutureGroup();
futureGroup.add(future1);
futureGroup.add(future2);
futureGroup.add(future3);

使用:

void main()  {
  Future<String> future1 = getData(2);
  Future<String> future2 = getData(4);
  Future<String> future3 = getData(6);
  FutureGroup futureGroup = FutureGroup();
  futureGroup.add(future1);
  futureGroup.add(future2);
  futureGroup.add(future3);
  futureGroup.close();
  futureGroup.future.then((value) => {print(value)});
}

Future<String> getData(int duration) async {
  await Future.delayed(Duration(seconds: duration)); //Mock delay
  return "This a test data";
}

输出:

I/flutter ( 5866): [This a test data, This a test data, This a testdata] // Called after 6 seconds.

注意:当所有“将来的任务”完成时，它将仅被调用一次，此处将在6秒钟后运行。