Question

我正在尝试创建一个倒数计时器应用程序，在该计时器中，我可以按一个按钮添加更多时间，而计时器在积极地倒计时，就像每个微波炉中都有一个按钮可以按一下以增加运行时间一样在不停止任何操作的情况下运行。

import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(
    home: new MyApp(),
  ));
}

class Countdown extends AnimatedWidget {
  Countdown({ Key key, this.animation }) : super(key: key, listenable: animation);
  Animation<int> animation;

  @override
  build(BuildContext context){
    return new Text(
      animation.value.toString(),
      style: new TextStyle(fontSize: 150.0),
    );
  }
}

class MyApp extends StatefulWidget {
  State createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> with TickerProviderStateMixin {
  AnimationController _controller;

  static const int kStartValue = 4;

  @override
  void initState() {
    super.initState();
    _controller = new AnimationController(
      vsync: this,
      duration: new Duration(seconds: kStartValue),
    );
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      floatingActionButton: new FloatingActionButton(
        child: new Icon(Icons.play_arrow),
        onPressed: () => _controller.forward(from: 0.0),
      ),
      body: new Container(
        child: new Center(
          child: new Countdown(
            animation: new StepTween(
              begin: kStartValue,
              end: 0,
            ).animate(_controller),
          ),
        ),
      ),
    );
  }
}

这个关于计时器的类似问题的示例对我来说很有意义，并且一直是我的出发点。我知道我需要更改持续时间，并用具有适当持续时间的新动画替换动画，但是我从来没有得到任何与我想要的正确行为相近的东西。

Answer 1

I think the below is what you're trying to accomplish. Tapping the FloatingActionButton adds 5 seconds.

import 'dart:async';
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Countdown Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Countdown Demo'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _timeRemaining = 10;
  Timer _timer;

  @override
  void initState() {
    _timer = Timer.periodic(Duration(seconds: 1), (Timer t) => _getTime());
    super.initState();
  }

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Text('$_timeRemaining'),
      ),
      floatingActionButton: FloatingActionButton(
          child: Icon(Icons.add),
          onPressed: () {
            _timeRemaining += 5;
          }),
    );
  }

  void _getTime() {
    setState(() {
      _timeRemaining == 0 ? _timeRemaining = 0 : _timeRemaining--;
    });
  }
}

在Flutter中倒数的过程中增加倒数计时器的时间

1 个答案: