对于Dart 2+语法，在异步函数上下文中:

import 'package:meta/meta.dart'; //for @required annotation

void main() async {
  void justWait({@required int numberOfSeconds}) async {
    await Future.delayed(Duration(seconds: numberOfSeconds));
  }

  await justWait(numberOfSeconds: 5);
} 

你也可以使用future .delayed工厂来完成延迟后的future。下面是两个函数在延迟后异步返回字符串的示例:

import 'dart:async';

Future sleep1() {
  return new Future.delayed(const Duration(seconds: 1), () => "1");
}

Future sleep2() {
  return new Future.delayed(const Duration(seconds: 2), () => "2");
}

它并不总是你想要的(有时你想要Future.delayed)，但如果你真的想在Dart命令行应用程序中睡觉，你可以使用Dart:io的sleep():

import 'dart:io';

main() {
  sleep(const Duration(seconds:1));
}

我发现在Dart中有几个实现可以使代码延迟执行:

new Future.delayed(const Duration(seconds: 1)); //recommend

new Timer(const Duration(seconds: 1), ()=>print("1 second later."));

sleep(const Duration(seconds: 1)); //import 'dart:io';

new Stream.periodic(const Duration(seconds: 1), (_) => print("1 second later.")).first.then((_)=>print("Also 1 second later."));
//new Stream.periodic(const Duration(seconds: 1)).first.then((_)=>print("Also 1 second later."));

这是一个有用的模拟，可以接受一个可选参数来模拟错误:

  Future _mockService([dynamic error]) {
    return new Future.delayed(const Duration(seconds: 2), () {
      if (error != null) {
        throw error;
      }
    });
  }

你可以这样使用它:

  await _mockService(new Exception('network error'));

对于Dart 2+语法，在异步函数上下文中:

import 'package:meta/meta.dart'; //for @required annotation

void main() async {
  void justWait({@required int numberOfSeconds}) async {
    await Future.delayed(Duration(seconds: numberOfSeconds));
  }

  await justWait(numberOfSeconds: 5);
}