Add time to countdown timer during while counting down in Flutter - dart

Question

I am trying to create a countdown timer application where I can press a button to add more time while the timer is actively counting down just like every microwave oven where there is a button you can press to add an extra minute to it's run time while it's running without stopping anything.
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),
),
),
),
);
}
}
This example from a similar question about timers makes sense to me and has been my jumping off point. I know I need to change the duration and replace the animation with a new one with the appropriate duration, but I never get anything close to the correct behavior I am looking for.

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--;
});
}
}