Dart avait Future，推迟特定行代码并执行其余代码

Question

想要推迟某些代码行，为此使用 await Future 并且效果很好，问题是它推迟了它之后的所有代码，我需要它在继续执行 rest 的同时推迟某些代码行立即输入代码

void main() async {
  for (int i = 0; i < 5; i++) {
       await Future.delayed(Duration(seconds: 1));
    //postpone just next line or few lines of code
    print('postpone this line of code ${i + 1}');
    print('postpone me too');
  }
  //should execute without being postponed
  print('continue imediately without being postponed by await Future');
}

这可以用 await Future 或其他函数实现吗？

Answer 1

await 它是注册 Future.then 回调的语法糖。使用 await 的目的是让所有后续代码更容易等待 Future 完成。如果那不是你想要的，你可以直接使用Future.then：

void main() {
  for (int i = 0; i < 5; i++) {
    Future.delayed(const Duration(seconds: 1)).then((_) {
      print('postpone this line of code ${i + 1}');
      print('postpone me too');
    });
  }
  print('continue immediately without being postponed by await Future');
}

由于Future.delayed需要回调，你也可以完全跳过then：

void main() {
  for (int i = 0; i < 5; i++) {
    Future.delayed(const Duration(seconds: 1), () {
      print('postpone this line of code ${i + 1}');
      print('postpone me too');
    });
  }
  print('continue immediately without being postponed by await Future');
}

如果你不使用创建的未来，这相当于使用 Timer:

import 'dart:async' show Timer;
void main() {
  for (int i = 0; i < 5; i++) {
    Timer(const Duration(seconds: 1), () {
      print('postpone this line of code ${i + 1}');
      print('postpone me too');
    });
  }
  print('continue immediately without being postponed by await Future');
}

Dart avait Future，推迟特定行代码并执行其余代码

Dart avait Future, postpone just certain line of code and execute the rest

future

async-await

dart