Flutter FutureBuilder不断被称为 [英] Flutter FutureBuilder gets constantly called

问题描述

我正在经历有趣的行为.我在有状态的小部件中有一个FutureBuilder.如果我一个人返回FutureBuilder，一切都会好起来的.我的API仅被调用一次. 但是，如果我添加了额外的逻辑，并在两个小部件之间进行选择-我可以在chrome中看到我的API被调用了数十次.我知道build方法可以随时执行，但是这种额外的逻辑如何完全破坏Future的行为呢?

I'm experiencing interesting behavior. I have a FutureBuilder in Stateful widget. If I return FutureBuilder alone, everything is ok. My API gets called only once. However, if I put extra logic, and make a choice between two widgets - I can see in chrome my API gets called tens of times. I know that build method executes at any time, but how does that extra logic completely breaks Future's behavior?

这里是api调用一次的示例.

Here is example of api calling once.

@override
  Widget build(BuildContext context) {
    return FutureBuilder(..);
}

以下是如果someBooleanFlag为false的api被多次调用的示例.

Here is example of api being called multiple times if someBooleanFlag is false.

@override
  Widget build(BuildContext context) {
    if(someBooleanFlag){
      return Text('Hello World');
    }
    else{
    return FutureBuilder(..);
}

谢谢

推荐答案

即使您的代码排在第一位，您仍然无法正确执行操作，正确的方法是:

Even if your code is working in first place, you are still not doing it properly, the correct way to do is:

// Create instance variable
Future myFuture;

@override
void initState() {
  super.initState();

  // assign this variable your Future
  myFuture = getFuture();
}

@override
Widget build(BuildContext context) {
  if (someBooleanFlag) {
    return Text('Hello World');
  } else {
    return FutureBuilder(
      future: myFuture, // use it like this
      ...
    );
  }
}

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