颤动倒数计时器

Question

如何将构造中传递的值放到第一个十进制数并显示在我的RaisedButton的子文本中？我试过但没有运气。我设法使用一个简单的定时器使回调函数工作但没有周期性，并且在文本中没有实时更新值...

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),
        ),
      ),
    );
  }
}

Answer 1

以下是使用Timer.periodic的示例：

按钮点击后倒计时从10开始到0：

import 'dart:async';

[...]

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;
        }
      },
    ),
  );
}

@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CountdownTimer库中的quiver.async类，使用更简单：

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")
      ],
    ),
  );
}

Answer 2

我已经创建了一个Generic Timer Widget，它可以用来显示任何类型的计时器，它也很灵活。

此Widget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. countDownStyle：您想要给定时器的任何样式
4. countDownFormatter：用户想要显示倒计时器的方式，例如hh mm ss字符串，如01 hours: 20 minutes: 45 seconds

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

//为此提供实现 - formatHHMMSS(duration.inSeconds);或使用我提供的下面的实现。

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;
              });
            },
            countDownStyle: 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";
}

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