Stopwatch 是一个秒表接口,用于测量经过的时间。结合 Timer 更新 UI
import 'package:flutter/material.dart';
import 'dart:async';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Stopwatch watch = new Stopwatch();
Timer timer;
String elapsedTime = '';
updateTime(Timer timer) {
if (watch.isRunning) {
setState(() {
elapsedTime = transformMilliSeconds(watch.elapsedMilliseconds);
});
}
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
centerTitle: true,
title: new Text('StopWatch'),
),
body: new Container(
padding: EdgeInsets.all(20.0),
child: new Column(
children: <Widget>[
new Text(elapsedTime, style: new TextStyle(fontSize: 25.0)),
SizedBox(height: 20.0),
new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new FloatingActionButton(
backgroundColor: Colors.green,
onPressed: startWatch,
child: new Icon(Icons.play_arrow)),
SizedBox(width: 20.0),
new FloatingActionButton(
backgroundColor: Colors.red,
onPressed: stopWatch,
child: new Icon(Icons.stop)),
SizedBox(width: 20.0),
new FloatingActionButton(
backgroundColor: Colors.blue,
onPressed: resetWatch,
child: new Icon(Icons.refresh)),
],
)
],
)));
}
startWatch() {
watch.start();
timer = new Timer.periodic(new Duration(milliseconds: 100), updateTime);
}
stopWatch() {
watch.stop();
setTime();
}
resetWatch() {
watch.reset();
setTime();
}
setTime() {
var timeSoFar = watch.elapsedMilliseconds;
setState(() {
elapsedTime = transformMilliSeconds(timeSoFar);
});
}
transformMilliSeconds(int milliseconds) {
//Thanks to Andrew
int hundreds = (milliseconds / 10).truncate();
int seconds = (hundreds / 100).truncate();
int minutes = (seconds / 60).truncate();
String minutesStr = (minutes % 60).toString().padLeft(2, '0');
String secondsStr = (seconds % 60).toString().padLeft(2, '0');
return "$minutesStr:$secondsStr";
}
}
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