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提问者：小点点

颤振倒计时定时器


我怎么做才能把值传递到结构中，使计时器四舍五入到第一个小数，并显示在我的RaisedButton的子文本？我尝试过，但没有运气。我设法使工作回调函数与一个简单的定时器，但没有周期性，没有实时更新的值在文本中…

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

class TimerButton extends StatefulWidget {
  final Duration timerTastoPremuto;


  TimerButton(this.timerTastoPremuto);

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

class _TimerButtonState extends State<TimerButton> {
  @override
  Widget build(BuildContext context) {
    return Container(
      margin: EdgeInsets.all(5.0),
      height: 135.0,
      width: 135.0,
      child: new RaisedButton(
        elevation: 100.0,
        color: Colors.white.withOpacity(.8),
        highlightElevation: 0.0,
        onPressed: () {
          int _start = widget.timerTastoPremuto.inMilliseconds;

          const oneDecimal = const Duration(milliseconds: 100);
          Timer _timer = new Timer.periodic(
              oneDecimal,
                  (Timer timer) =>
                  setState(() {
                    if (_start < 100) {
                      _timer.cancel();
                    } else {
                      _start = _start - 100;
                    }
                  }));

        },
        splashColor: Colors.red,
        highlightColor: Colors.red,
        //shape: RoundedRectangleBorder e tutto il resto uguale
        shape: BeveledRectangleBorder(
            side: BorderSide(color: Colors.black, width: 2.5),
            borderRadius: new BorderRadius.circular(15.0)),
        child: new Text(
          "$_start",
          style: new TextStyle(fontFamily: "Minim", fontSize: 50.0),
        ),
      ),
    );
  }
}

共3个答案

匿名用户

这是一个使用Timer.周期性的示例：

倒计时从10到0点击按钮：

import 'dart:async';

[...]

Timer _timer;
int _start = 10;

void startTimer() {
  const oneSec = const Duration(seconds: 1);
  _timer = new Timer.periodic(
    oneSec,
    (Timer timer) {
      if (_start == 0) {
        setState(() {
          timer.cancel();
        });
      } else {
        setState(() {
          _start--;
        });
      }
    },
  );
}

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

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")
      ],
    ),
  );
}

结果：

您还可以使用quiver. async库中的CountdownTimer类，用法更简单：

import 'package:quiver/async.dart';

[...]

int _start = 10;
int _current = 10;

void startTimer() {
  CountdownTimer countDownTimer = new CountdownTimer(
    new Duration(seconds: _start),
    new Duration(seconds: 1),
  );

  var sub = countDownTimer.listen(null);
  sub.onData((duration) {
    setState(() { _current = _start - duration.elapsed.inSeconds; });
  });

  sub.onDone(() {
    print("Done");
    sub.cancel();
  });
}

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

编辑：对于评论中关于按钮点击行为的问题

使用上面的代码，它使用定时器。周期性，每个按钮点击都会启动一个新的定时器，所有这些定时器都会更新相同的_start变量，从而导致更快的计数器递减。

有多种解决方案可以更改此行为，具体取决于您想要实现的目标：

  • 单击后禁用按钮，以便用户不再打扰倒计时（可能会在计时器取消后重新启用它）
  • 用非空条件包装Timer.周期创建，这样多次点击按钮没有效果
if (_timer != null) {
  _timer = new Timer.periodic(...);
}
  • 如果您想在每次单击时重新启动计时器，请取消计时器并重置倒计时：
if (_timer != null) {
  _timer.cancel();
  _start = 10;
}
_timer = new Timer.periodic(...);
  • 如果您希望按钮像播放/暂停按钮一样：
if (_timer != null) {
  _timer.cancel();
  _timer = null;
} else {
  _timer = new Timer.periodic(...);
}

您还可以使用这个官方的异步包，它提供了一个从Timer扩展并添加重置方法的RestartableTimer类。

所以只要调用_timer。重置（）；在每个按钮单击时。

最后，Codeben现在支持Flutter！所以这里有一个实时示例，以便每个人都可以使用它：https://codepen.io/Yann39/pen/oNjrVOb

匿名用户

我创建了一个通用定时器小部件，可用于显示任何类型的定时器及其灵活性。

此小部件具有以下属性

  1. 秒剩余：计时器需要以秒为单位运行的持续时间
  2. whenTimeExpires：如果计时器完成，需要执行什么操作
  3. count tDownStyle：您想给计时器的任何类型的样式
  4. count tDownFor物质：用户想要显示倒计时计时器的方式，例如hh mm ss字符串，如01小时：20分钟：45秒

您可以提供默认格式化程序（formatHHMMSS），以防您不想从每个地方都提供它。

//为此提供实现-formatHHMMSS（时间. in秒）；或使用下面我提供的一个。

import 'package:flutter/material.dart';
class CountDownTimer extends StatefulWidget {
  const CountDownTimer({
    Key key,
    int secondsRemaining,
    this.countDownTimerStyle,
    this.whenTimeExpires,
    this.countDownFormatter,
  })  : secondsRemaining = secondsRemaining,
        super(key: key);

  final int secondsRemaining;
  final Function whenTimeExpires;
  final Function countDownFormatter;
  final TextStyle countDownTimerStyle;

  State createState() => new _CountDownTimerState();
}

class _CountDownTimerState extends State<CountDownTimer>
    with TickerProviderStateMixin {
  AnimationController _controller;
  Duration duration;

  String get timerDisplayString {
    Duration duration = _controller.duration * _controller.value;
    return widget.countDownFormatter != null
        ? widget.countDownFormatter(duration.inSeconds)
        : formatHHMMSS(duration.inSeconds);
      // In case user doesn't provide formatter use the default one
     // for that create a method which will be called formatHHMMSS or whatever you like
  }

  @override
  void initState() {
    super.initState();
    duration = new Duration(seconds: widget.secondsRemaining);
    _controller = new AnimationController(
      vsync: this,
      duration: duration,
    );
    _controller.reverse(from: widget.secondsRemaining.toDouble());
    _controller.addStatusListener((status) {
      if (status == AnimationStatus.completed || status == AnimationStatus.dismissed) {
        widget.whenTimeExpires();
      }
    });
  }

  @override
  void didUpdateWidget(CountDownTimer oldWidget) {
    if (widget.secondsRemaining != oldWidget.secondsRemaining) {
      setState(() {
        duration = new Duration(seconds: widget.secondsRemaining);
        _controller.dispose();
        _controller = new AnimationController(
          vsync: this,
          duration: duration,
        );
        _controller.reverse(from: widget.secondsRemaining.toDouble());
        _controller.addStatusListener((status) {
          if (status == AnimationStatus.completed) {
            widget.whenTimeExpires();
          } else if (status == AnimationStatus.dismissed) {
            print("Animation Complete");
          }
        });
      });
    }
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new Center(
        child: AnimatedBuilder(
            animation: _controller,
            builder: (_, Widget child) {
              return Text(
                timerDisplayString,
                style: widget.countDownTimerStyle,
              );
            }));
  }
}

用法：

 Container(
       width: 60.0,
       padding: EdgeInsets.only(top: 3.0, right: 4.0),
         child: CountDownTimer(
           secondsRemaining: 30,
           whenTimeExpires: () {
              setState(() {
                hasTimerStopped = true;
              });
            },
            countDownTimerStyle: TextStyle(
                color: Color(0XFFf5a623),
                fontSize: 17.0,
                height: 1.2,
            ),
          ),
        )

formatHHMMSS的示例：

String formatHHMMSS(int seconds) {
  int hours = (seconds / 3600).truncate();
  seconds = (seconds % 3600).truncate();
  int minutes = (seconds / 60).truncate();

  String hoursStr = (hours).toString().padLeft(2, '0');
  String minutesStr = (minutes).toString().padLeft(2, '0');
  String secondsStr = (seconds % 60).toString().padLeft(2, '0');

  if (hours == 0) {
    return "$minutesStr:$secondsStr";
  }

  return "$hoursStr:$minutesStr:$secondsStr";
}

上述代码的空安全版本

import 'package:flutter/material.dart';

class CountDownTimer extends StatefulWidget {
  const CountDownTimer({
    Key? key,
    required this.secondsRemaining,
    required this.whenTimeExpires,
    this.countDownFormatter,
    this.countDownTimerStyle,
  }) : super(key: key);

  final int secondsRemaining;
  final VoidCallback whenTimeExpires;
  final TextStyle? countDownTimerStyle;
  final Function(int seconds)? countDownFormatter;

  @override
  State createState() => _CountDownTimerState();
}

class _CountDownTimerState extends State<CountDownTimer>
    with TickerProviderStateMixin {
  late final AnimationController _controller;
  late final Duration duration;

  String get timerDisplayString {
    final duration = _controller.duration! * _controller.value;
    if (widget.countDownFormatter != null) {
      return widget.countDownFormatter!(duration.inSeconds) as String;
    } else {
      return formatHHMMSS(duration.inSeconds);
    }
  }

  String formatHHMMSS(int seconds) {
    final hours = (seconds / 3600).truncate();
    seconds = (seconds % 3600).truncate();
    final minutes = (seconds / 60).truncate();

    final hoursStr = (hours).toString().padLeft(2, '0');
    final minutesStr = (minutes).toString().padLeft(2, '0');
    final secondsStr = (seconds % 60).toString().padLeft(2, '0');

    if (hours == 0) {
      return '$minutesStr:$secondsStr';
    }

    return '$hoursStr:$minutesStr:$secondsStr';
  }

  @override
  void initState() {
    super.initState();
    duration = Duration(seconds: widget.secondsRemaining);
    _controller = AnimationController(
      vsync: this,
      duration: duration,
    );
    _controller
      ..reverse(from: widget.secondsRemaining.toDouble())
      ..addStatusListener((status) {
        if (status == AnimationStatus.completed ||
            status == AnimationStatus.dismissed) {
          widget.whenTimeExpires();
        }
      });
  }

  @override
  void didUpdateWidget(CountDownTimer oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.secondsRemaining != oldWidget.secondsRemaining) {
      setState(() {
        duration = Duration(seconds: widget.secondsRemaining);
        _controller.dispose();
        _controller = AnimationController(
          vsync: this,
          duration: duration,
        );
        _controller
          ..reverse(from: widget.secondsRemaining.toDouble())
          ..addStatusListener((status) {
            if (status == AnimationStatus.completed) {
              widget.whenTimeExpires();
            }
          });
      });
    }
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: AnimatedBuilder(
        animation: _controller,
        builder: (_, Widget? child) {
          return Text(
            timerDisplayString,
            style: widget.countDownTimerStyle,
          );
        },
      ),
    );
  }
}

匿名用户

派对有点晚了，但是你们为什么不试试animation.No我不是告诉你们管理动画控制器并把它们都处理掉，还有一个内置的小部件叫做Tween动画生成器。你可以在任何类型的值之间制作动画，这里有一个Duration类的例子

TweenAnimationBuilder<Duration>(
  duration: Duration(minutes: 3),
  tween: Tween(begin: Duration(minutes: 3), end: Duration.zero),
  onEnd: () {
    print('Timer ended');
  },
  builder: (BuildContext context, Duration value, Widget? child) {
    final minutes = value.inMinutes;
    final seconds = value.inSeconds % 60;
    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 5),
      child: Text('$minutes:$seconds',
               textAlign: TextAlign.center,
               style: TextStyle(
               color: Colors.black,
               fontWeight: FontWeight.bold,
               fontSize: 30)));
    }),

并且您还会收到onEnd回电，当动画完成时通知您；

这是输出

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