在 Flutter 中倒計時期間為倒計時計時器添加時間

Question

我正在嘗試創建一個倒數計時器應用程序，我可以按下一個按鈕來增加更多時間，而計時器正在主動倒計時，就像每個微波爐都有一個按鈕，您可以按下按鈕以在它的運行時間上增加一分鍾不停止任何東西的運行。

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),
          ),
        ),
      ),
    );
  }
}

這個來自有關計時器的類似問題的示例對我來說很有意義，並且一直是我的起點。 我知道我需要更改持續時間並將動畫替換為具有適當持續時間的新動畫，但我從來沒有得到任何接近我正在尋找的正確行為的東西。

Answer 1

我認為下面是你想要完成的。 點擊FloatingActionButton增加 5 秒。

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--;
    });
  }
}