颤振倒数计时器 [英] Flutter Countdown Timer
问题描述
如何将传递的值放入构造中,制作一个四舍五入到第一个小数并显示在我的 RaisedButton 的子文本中的计时器?我试过,但没有运气.我设法使用一个简单的 Timer 使回调函数工作,但没有周期性,也没有在文本中实时更新值...
import 'package:flutter/material.dart';导入飞镖:UI";导入飞镖:异步";类 TimerButton 扩展了 StatefulWidget {最终持续时间计时器TastoPremuto;定时器按钮(this.timerTastoPremuto);@覆盖_TimerButtonState createState() =>_TimerButtonState();}class _TimerButtonState 扩展 State{@覆盖小部件构建(BuildContext 上下文){返回容器(边距:EdgeInsets.all(5.0),高度:135.0,宽度:135.0,孩子:新的凸起按钮(海拔:100.0,颜色:Colors.white.withOpacity(.8),高亮高度:0.0,按下: () {int _start = widget.timerTastoPremuto.inMilliseconds;const oneDecimal = const 持续时间(毫秒:100);定时器_timer = new Timer.periodic(一个十进制,(定时器定时器) =>设置状态((){如果 (_start <100) {_timer.cancel();} 别的 {_start = _start - 100;}}));},splashColor: Colors.red,highlightColor: Colors.red,//形状:RoundedRectangleBorder e tutto il resto uguale形状:斜角矩形边框(边:BorderSide(颜色:Colors.black,宽度:2.5),borderRadius:新的 BorderRadius.circular(15.0)),孩子:新文本("$_start",样式:new TextStyle(fontFamily: "Minim", fontSize: 50.0),),),);}}
这里是一个使用
您还可以使用 CountdownTimer 类从 <一个 href="https://api.flutter.dev/flutter/quiver.async/quiver.async-library.html" rel="noreferrer">quiver.async 库,使用起来更简单:>
import 'package:quiver/async.dart';[...]int_start = 10;int_current = 10;无效的开始定时器(){CountdownTimer countDownTimer = new CountdownTimer(新的持续时间(秒:_start),新的持续时间(秒:1),);var sub = countDownTimer.listen(null);sub.onData((持续时间){setState(() { _current = _start - duration.elapsed.inSeconds; });});sub.onDone(() {打印(完成");子取消();});}小部件构建(BuildContext 上下文){返回新的脚手架(appBar: AppBar(title: Text("Timer test")),正文:列(孩子们:<小部件>[凸起按钮(按下: () {开始定时器();},孩子:文本(开始"),),文本($_current")],),);}
EDIT:关于按钮点击行为评论中的问题
使用上面使用Timer.periodic
的代码,每次点击按钮时都会启动一个新的计时器,并且所有这些计时器都会更新相同的_start
变量,导致计数器下降速度更快.
有多种解决方案可以改变这种行为,具体取决于您想要实现的目标:
- 一旦点击就禁用按钮,这样用户就不会再打扰倒计时(可能会在定时器取消后重新启用)
- 使用非空条件包装
Timer.periodic
创建,以便多次单击按钮无效
if (_timer != null) {_timer = new Timer.periodic(...);}
- 如果您想在每次点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();_开始= 10;}_timer = new Timer.periodic(...);
- 如果你想让按钮像播放/暂停按钮一样:
if (_timer != null) {_timer.cancel();_timer = 空;} 别的 {_timer = new Timer.periodic(...);}
您也可以使用这个官方 async 包,它提供了一个 RestartableTimer 类从 Timer
扩展并添加了 reset代码>方法.
所以只需在每次点击按钮时调用 _timer.reset();
.
终于,Codepen 现在支持 Flutter 了!所以这是一个活生生的例子,这样每个人都可以玩它:https://codepen.io/Yann39/pen/oNjrVOb
How can I do to put the value passed in the construction, to make a timer that rounds to the first decimal and shows at the child text of my RaisedButton? I've tried but without luck. I manage to make work the callback function with a simple Timer but no periodic and with no update of value in real time in the text...
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(
"$_start",
style: new TextStyle(fontFamily: "Minim", fontSize: 50.0),
),
),
);
}
}
Here is an example using Timer.periodic :
Countdown starts from 10
to 0
on button click :
import 'dart:async';
[...]
Timer _timer;
int _start = 10;
void startTimer() {
const oneSec = const Duration(seconds: 1);
_timer = new Timer.periodic(
oneSec,
(Timer timer) {
if (_start == 0) {
setState(() {
timer.cancel();
});
} else {
setState(() {
_start--;
});
}
},
);
}
@override
void dispose() {
_timer.cancel();
super.dispose();
}
Widget build(BuildContext context) {
return new Scaffold(
appBar: AppBar(title: Text("Timer test")),
body: Column(
children: <Widget>[
RaisedButton(
onPressed: () {
startTimer();
},
child: Text("start"),
),
Text("$_start")
],
),
);
}
Result :
You can also use the CountdownTimer class from the quiver.async library, usage is even simpler :
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")
],
),
);
}
EDIT : For the question in comments about button click behavior
With the above code which uses Timer.periodic
, a new timer will indeed be started on each button click, and all these timers will update the same _start
variable, resulting in a faster decreasing counter.
There are multiple solutions to change this behavior, depending on what you want to achieve :
- disable the button once clicked so that the user could not disturb the countdown anymore (maybe enable it back once timer is cancelled)
- wrap the
Timer.periodic
creation with a non null condition so that clicking the button multiple times has no effect
if (_timer != null) {
_timer = new Timer.periodic(...);
}
- cancel the timer and reset the countdown if you want to restart the timer on each click :
if (_timer != null) {
_timer.cancel();
_start = 10;
}
_timer = new Timer.periodic(...);
- if you want the button to act like a play/pause button :
if (_timer != null) {
_timer.cancel();
_timer = null;
} else {
_timer = new Timer.periodic(...);
}
You could also use this official async package which provides a RestartableTimer class which extends from Timer
and adds the reset
method.
So just call _timer.reset();
on each button click.
Finally, Codepen now supports Flutter ! So here is a live example so that everyone can play with it : https://codepen.io/Yann39/pen/oNjrVOb
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