暂停颤振倒数计时器

Question

我一直在玩 Dart Timer Class，我让它以非常基本的形式工作，但是我试图向它添加暂停功能。 我查看了他们的文档，但他们对 Timer 类的了解并不多......

有什么办法可以在点击时暂停和恢复计时器/倒计时？ 这是我迄今为止取得的成就：

import 'package:flutter/material.dart';
import 'dart:async';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}


class _MyHomePageState extends State<MyHomePage> {

  Timer _timer;
  int _start = 10;

  void startTimer() {
    const oneSec = const Duration(seconds: 1);
    _timer = new Timer.periodic(
        oneSec,
            (Timer timer) => setState(() {
          if (_start < 1) {
            timer.cancel();
          } else {
            _start = _start - 1;
          }
        }));
  }


  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: AppBar(title: Text("Timer test")),
        body: Column(
          children: <Widget>[
            RaisedButton(
              onPressed: () {
                startTimer();
              },
              child: Text("start"),
            ),
            Text("$_start")
          ],
        ));
  }
}

Answer 1

没有内置的pause功能，因为Timer类主要用于为以后调度代码块。

你的用例是什么？ Stopwatch类具有暂停和恢复功能。

Answer 2

带有暂停和振动的工作颤振示例如下（ 来源）

import 'package:flutter/material.dart';
import 'dart:async';
import 'package:vibration/vibration.dart';

void main() => runApp(MaterialApp(home: CountdownCard()));

class CountdownCard extends StatefulWidget {
// This widget is the root of your application.

@override
_CountdownCardState createState() => _CountdownCardState();
}

class _CountdownCardState extends State<CountdownCard> {
Timer _timer;
int _start = 0;
bool _vibrationActive = false;

void startTimer(int timerDuration) {
    if (_timer != null) {
    _timer.cancel();
    cancelVibrate();
    }
    setState(() {
    _start = timerDuration;
    });
    const oneSec = const Duration(seconds: 1);
    print('test');
    _timer = new Timer.periodic(
    oneSec,
    (Timer timer) => setState(
        () {
        if (_start < 1) {
            timer.cancel();
            print('alarm');
            vibrate();
        } else {
            _start = _start - 1;
        }
        },
    ),
    );
}

void cancelVibrate() {
    _vibrationActive = false;
    Vibration.cancel();
}

void vibrate() async {
    _vibrationActive = true;
    if (await Vibration.hasVibrator()) {
    while (_vibrationActive) {
        Vibration.vibrate(duration: 1000);
        await Future.delayed(Duration(seconds: 2));
    }
    }
}

void pauseTimer() {
    if (_timer != null) _timer.cancel();
}

void unpauseTimer() => startTimer(_start);

@override
void dispose() {
    _timer.cancel();
    super.dispose();
}

@override
Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
        title: Text('Countdown'),
        ),
        body: Wrap(children: <Widget>[
        Column(
            children: <Widget>[
            RaisedButton(
                onPressed: () {
                startTimer(10);
                },
                child: Text("start"),
            ),
            Text("$_start"),
            RaisedButton(
                onPressed: () {
                pauseTimer();
                },
                child: Text("pause"),
            ),
            RaisedButton(
                onPressed: () {
                unpauseTimer();
                },
                child: Text("unpause"),
            ),
            RaisedButton(
                onPressed: () {
                cancelVibrate();
                },
                child: Text("stop alarm"),
            ),
            ],
        ),
        ]));
}
}

Answer 3

我刚刚上传了这个包来实现这个： https : //pub.dev/packages/pausable_timer

// It starts paused
final timer = PausableTimer(Duration(seconds: 1), () => print('Fired!'));
timer.start();
timer.pause();
timer.start();

Dart 本身也存在请求该功能的问题，但看起来不会很快添加。

Answer 4

我们在页面打开时定义启动计时器的变量。 页面关闭时计时器关闭。

如果触摸屏幕，可变持续时间变为真，计时器停止倒计时

     Timer? _timer;
     int _start = 200;
     bool duration = false;
     Duration oneSec = const Duration(milliseconds: 10);
    

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    startTimer();
  }

  @override
  void dispose() {
    _timer!.cancel();
    super.dispose();
  }

 ```

    GestureDetector(
              onTap: () {},
              onTapDown: (e) {
                setState(() {
                  duration = true;
                });
              },
              onHorizontalDragEnd: (e) {
                Navigator.pop(context);
              },
              onTapUp: (e) {
                setState(() {
                  duration = false;
                });
              },
              child:Text("demo page")}

  void startTimer() {
    _timer = new Timer.periodic(
      oneSec,
      (Timer timer) {
        if (_start == 0) {
          setState(() {
            timer.cancel();
            Navigator.pop(context);
          });
        } else {
          setState(() {
            duration == false ? _start-- : null;
          });
        }
      },
    );
  }
}