如何在 Dart 中运行重复出现的函数? [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，中间有延迟.我怎样才能用 Dart 做到这一点?

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

推荐答案

您可以使用 Timer 类来安排一次性和重复功能.

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

以下是运行重复函数的方法:

Here is how you run a repeating function:

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

Timer 有两个参数，一个持续时间和一个要运行的函数.持续时间必须是 Duration 的一个实例.回调必须采用单个参数，即计时器本身.

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.

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

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

在延迟后安排一次性函数(执行一次，在未来的某个时间):

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

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

请注意，一次性定时器的回调不带参数.

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

你也可以要求尽快运行一个函数，至少在未来一个事件循环周期.

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!'));
}

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在 HTML 中

定时器甚至可以在 HTML 中工作.事实上，window.setTimeout 被移除了，所以 Timer 是未来运行函数的唯一途径.

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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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