颤动倒数计时器 [英] Flutter Countdown Timer
问题描述
我该如何将传递的值放入构造中,以使计时器四舍五入到小数点后第一位并显示在RaisedButton的子文本中?我尝试过但没有运气。我设法用一个简单的Timer来使回调函数起作用,但是没有周期性,并且文本中没有实时的值更新...
import'package:flutter / material.dart';
导入 dart:ui;
导入 dart:async;
类TimerButton扩展了StatefulWidget {
final Duration timerTastoPremuto;
TimerButton(this.timerTastoPremuto);
@override
_TimerButtonState createState()=> _TimerButtonState();
}
类_TimerButtonState扩展了State< TimerButton> {
@override
Widget build(BuildContext context){
return Container(
margin:EdgeInsets.all(5.0),
height:135.0,
宽度:135.0,
子级:new RaisedButton(
高程:100.0,
颜色:Colors.white.withOpacity(.8),
高亮高度:0.0,
onPressed :(){
int _start = widget.timerTastoPremuto.inMilliseconds;
const oneDecimal = const Duration(毫秒: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 ,
//形状:RoundedRectangleBorder和其他形状
形状:BeveledRectangleBorder(
侧面:BorderSide(color:Colors.black,width:2.5),
borderRadius:new BorderRadius .circular(15.0)),
子项:new Text(
$ _start,
样式:new TextStyle(fontFamily: Minim,fontSize:50.0),
) ,
),
);
}
}
此处是使用
您还可以使用 CountdownTimer 类,来自 quiver.async 库,用法甚至更简单:
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();
});
}
窗口小部件build(BuildContext context){
返回新的Scaffold(
appBar:AppBar(title:Text( Timer test))),
正文:列(
子项:< Widget> [
RaisedButton(
onPressed:(){
startTimer();
},
子项:Text( start),
),
Text( $ _ current)
],
),
);
}
编辑:有关按钮单击行为的注释中的问题
使用上面的代码使用 Timer.periodic
,则确实会在每次按钮单击时启动一个新计时器,所有这些计时器都将更新相同的 _start
变量,从而使计数器减少的速度更快。
有多种解决方案可以更改此行为,具体取决于您要实现的目标:
- 禁用单击一次按钮,以便用户不再打扰倒计时(也许在取消计时器后可以重新启用倒计时)
- 包装
Timer.periodic
使用非null条件创建,因此多次单击按钮无效
if(_timer!= null){
_timer = new Timer.periodic(...);
}
- 取消计时器并重置倒计时想要在每次单击时重新启动计时器:
if( _timer!= null){
_timer.cancel();
_start = 10;
}
_timer = new Timer.periodic(...);
- 如果您希望按钮像播放/暂停按钮那样起作用:
if(_timer!= null){
_timer.cancel();
_timer = null;
} else {
_timer = new Timer.periodic(...);
}
您也可以使用此官方 async 软件包,其中提供了 RestartableTimer 类,它从 Timer
扩展并添加了 reset
方法。
因此,每次单击按钮只需调用 _timer.reset();
。
最后,Codepen现在支持Flutter!因此,这是一个实时示例,每个人都可以使用它: 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(
"$_start",
style: new TextStyle(fontFamily: "Minim", fontSize: 50.0),
),
),
);
}
}
Here is an example using Timer.periodic :
Countdown starts from 10
to 0
on button click :
import 'dart:async';
[...]
Timer _timer;
int _start = 10;
void startTimer() {
const oneSec = const Duration(seconds: 1);
_timer = new Timer.periodic(
oneSec,
(Timer timer) => setState(
() {
if (_start < 1) {
timer.cancel();
} else {
_start = _start - 1;
}
},
),
);
}
@override
void dispose() {
_timer.cancel();
super.dispose();
}
Widget build(BuildContext context) {
return new Scaffold(
appBar: AppBar(title: Text("Timer test")),
body: Column(
children: <Widget>[
RaisedButton(
onPressed: () {
startTimer();
},
child: Text("start"),
),
Text("$_start")
],
),
);
}
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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