如何在Dart中运行重复功能？ [英] How do I run a reoccurring function, in Dart?

问题描述

我想一遍又一遍地运行一个函数，但要间隔一段时间。如何使用Dart做到这一点？

解决方案

您可以使用 Timer 类来安排单发和重复功能。

重复

这是运行重复功能的方式：

  import'dart：async'; 
 main（）{
 const oneSec = const Duration（seconds：1）; 
 new Timer.periodic（oneSec，（Timer t）=> print（’hi！’））; 
} 
  

Timer需要两个参数，一个持续时间和一个要运行的函数。持续时间必须是 Duration 的实例。回调必须使用单个参数，即计时器本身。

取消重复计时器

使用 timer.cancel（）取消重复计时器。这是计时器将计时器从重复计时器传递到回调运行的原因之一。

延迟后一次拍摄

要在延迟后安排一次功能（执行一次，以后再执行一次）：

  import'dart：async'; 
 main（）{
 const 20.Millis = const持续时间（毫秒：20）； 
 new Timer（twentyMillis，（）=> print（’hi！’））; 
} 
  

请注意，单次计时器的回调不带参数。 / p>

尽快拍摄

您还可以要求尽快运行某个函数，

  import'dart：async'; 
 main（）{
 Timer.run（（）=> print（’hi！’））; 
} 
  

在HTML中

计时器甚至可以HTML格式工作。实际上， window.setTimeout 已被删除，因此Timer是将来运行函数的唯一方法。

I'd like to run a function over and over, with a delay in between. How can I do this with Dart?

解决方案

You can use the Timer class to schedule one-shot and repeating functions.

Repeating

Here is how you run a repeating function:

import 'dart:async';
main() {
  const oneSec = const Duration(seconds:1);
  new Timer.periodic(oneSec, (Timer t) => print('hi!'));
}

The Timer takes two arguments, a duration and a function to run. The duration must be an instance of Duration. The callback must take a single parameter, the timer itself.

Canceling a repeating timer

Use timer.cancel() to cancel a repeating timer. This is one reason why timer is passed to the callback run from a repeating timer.

One-shot after a delay

To schedule a one-shot function after a delay (execute once, some time in the future):

import 'dart:async';
main() {
  const twentyMillis = const Duration(milliseconds:20);
  new Timer(twentyMillis, () => print('hi!'));
}

Notice the callback for a one-shot timer does not take a parameter.

One-shot as soon as possible

You can also request that a function is run as soon as possible, at least one event-loop tick in the future.

import 'dart:async';
main() {
  Timer.run(() => print('hi!'));
}

In HTML

Timers even work in HTML. In fact, window.setTimeout was removed, so Timer is the only way to run a function in the future.

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