Flutter可暂停计时器插件pausable_timer的使用

简介

pausable_timer 是一个Dart库，提供了可以暂停、恢复和重置的定时器功能。这个库非常适合需要精确控制时间的应用场景，比如游戏开发中的倒计时、任务调度等。

安装

在 pubspec.yaml 文件中添加依赖：

dependencies:
  pausable_timer: ^latest_version # 替换为最新版本号

然后运行 flutter pub get 来安装包。

示例代码

基本用法

下面是一个简单的例子，演示了如何创建、启动、暂停、恢复和取消一个定时器：

import 'package:pausable_timer/pausable_timer.dart';

void main() async {
  print('Create a timer that fires in 1 second, but it is not started yet');
  final timer = PausableTimer(Duration(seconds: 1), () => print('Fired!'));
  print('So we start it');
  timer.start();

  print('And wait 1/2 second...');
  await Future<void>.delayed(timer.duration ~/ 2);
  print('Not yet fired, still 1/2 second to go!');

  print('We can pause it now');
  timer.pause();

  // When paused, time can pass but the timer won't be fired
  print('And we wait a whole second...');
  await Future<void>.delayed(timer.duration);
  print("But our timer doesn't care while it's paused");
  print('It will still wait for ${timer.duration - timer.elapsed} after '
      "it's started again");

  print('So we start it again');
  timer.start();
  print('And wait for 1/2 second again, it should have fired when we are done');
  await Future<void>.delayed(timer.duration ~/ 2);
  print('And we are done, "Fired!" should be up there 👆');
  print('Now our timer completed ${timer.tick} tick');

  print('We can reset it if we want to use it again');
  timer.reset();
  print('We have to start it again after the reset because it was not running');
  timer.start();
  print('Now we wait a whole second in one go...');
  await Future<void>.delayed(timer.duration);
  print('And we are done, so you should see "Fired!" up there again 👆');
  print('Now the timer has ${timer.tick} ticks');

  print('We can reset it and start it again');
  timer.reset();
  timer.start();

  print('And you can cancel it too, so it will not fire again');
  timer.cancel();
  print("After a timer is cancelled, it can't be used again");
  print('But important information can still be retrieved:');
  print('duration: ${timer.duration}');
  print('elapsed: ${timer.elapsed}');
  print('tick: ${timer.tick}');
  print('isPaused: ${timer.isPaused}');
  print('isActive: ${timer.isActive}');
  print('isExpired: ${timer.isExpired}');
  print('isCancelled: ${timer.isCancelled}');
}

倒计时实现

接下来是一个更复杂的例子，展示了如何使用 PausableTimer.periodic 实现一个可以暂停的倒计时：

import 'dart:async';
import 'package:pausable_timer/pausable_timer.dart';

void main() async {
  late final PausableTimer timer;
  var countDown = 5;

  print('Create a periodic timer that fires every 1 second and starts it');
  timer = PausableTimer.periodic(
    Duration(seconds: 1),
        () {
      countDown--;

      if (countDown == 0) {
        timer.pause();
      }

      print('\t$countDown');
    },
  )..start();

  print('And wait 2.1 seconds...');
  print('(0.1 extra to make sure there is no race between the timer and the '
      'waiting here)');
  await Future<void>.delayed(timer.duration * 2.1);
  print('By now 2 events should have fired: 4, 3\n');

  print('We can pause it now');
  timer.pause();

  print('And we wait for 2 more seconds...');
  await Future<void>.delayed(timer.duration * 2);
  print("But our timer doesn't care while it's paused\n");

  print('So we start it again');
  timer.start();
  print('And wait for 3.1 seconds more...');
  await Future<void>.delayed(timer.duration * 3.1);
  print('And we are done: 2, 1 and 0 should have been printed');

  print('The timer should be unpaused, inactive, expired and not cancelled');
  print('isPaused: ${timer.isPaused}');
  print('isActive: ${timer.isActive}');
  print('isExpired: ${timer.isExpired}');
  print('isCancelled: ${timer.isCancelled}');

  print('We can now reset it and start it again, now for 3 seconds');
  countDown = 3;
  timer
    ..reset()
    ..start();
  print('And wait for 3.1 seconds...');
  await Future<void>.delayed(timer.duration * 3.1);
  print('And it should be done printing: 2, 1 and 0');
}

总结

pausable_timer 提供了一种灵活的方式来管理定时器的行为，包括暂停、恢复和重置等功能。通过上述示例，您可以更好地理解如何在Flutter应用中使用这个强大的工具。希望这些信息对您有所帮助！如果有任何问题或需要进一步的帮助，请随时提问。