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test_progress_time_page.dart
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test_progress_time_page.dart
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import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'dart:async';
void main() {
runApp(RootPage());
}
class RootPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: TestTimeProgressIndicatorPage(),
);
}
}
///通过流 Stream 实现的倒计时功能
///倒计时
class TestTimeProgressIndicatorPage extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return _TestABPageState();
}
}
class _TestABPageState extends State {
///单订阅流
StreamController<double> _streamController = StreamController();
///计时器
Timer _timer;
///倒计时6秒
double totalTimeNumber = 6000;
///当前的时间
double currentTimeNumber = 6000;
@override
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
///当前页面绘制完第一帧后回调
///在这里开启定时器
startTimer();
});
}
@override
void dispose() {
super.dispose();
///关闭
_streamController.close();
_timer.cancel();
}
void startTimer() {
///间隔100毫秒执行时间
_timer = Timer.periodic(Duration(milliseconds: 100), (timer) {
///间隔100毫秒执行一次 每次减100
currentTimeNumber -= 100;
///如果计完成取消定时
if (currentTimeNumber <= 0) {
_timer.cancel();
currentTimeNumber = 0;
}
///流数据更新
_streamController.add(currentTimeNumber);
});
}
@override
Widget build(BuildContext context) {
///页面主体脚手架
return Scaffold(
appBar: AppBar(
title: Text("测试Stream "),
),
body: Column(
children: [
///圆圈部分
Container(
child: buildStreamBuilder(),
margin: EdgeInsets.only(top: 20, left: 20),
),
///间隔
SizedBox(
height: 40,
),
///Demo的控制按钮
OutlineButton(
child: Text('开始倒计时'),
onPressed: () {
currentTimeNumber = totalTimeNumber;
if (!_timer.isActive) {
startTimer();
}
},
)
],
),
);
}
/// 监听Stream,每次值改变的时候,更新Text中的内容
StreamBuilder<double> buildStreamBuilder() {
return StreamBuilder<double>(
///绑定stream
stream: _streamController.stream,
///默认的数据
initialData: 0,
///构建绑定数据的UI
builder: (BuildContext context, AsyncSnapshot<double> snapshot) {
return Stack(
///子Widget 居中对齐
alignment: Alignment.center,
children: [
///中间显示的文本
Text(
(snapshot.data / 1000).toStringAsFixed(0),
style: TextStyle(fontSize: 22, color: Colors.blue),
),
///圆圈进度
CircularProgressIndicator(
value: 1.0 - snapshot.data / totalTimeNumber,)
],
);
},
);
}
}