如何在颤动中停止动画持续时间

Question

我这里有一段关于递减计时器的代码。我想在5秒后或某个特定时间停止计时器。如何通过颤动来实现这一点？这是一个示例代码。

class MyHomePage1 extends StatefulWidget {
MyHomePage1({Key key, this.title}) : super(key: key);

final String title;

@override
_MyHomePage1State createState() => _MyHomePage1State();
}

class _MyHomePage1State extends State<MyHomePage1> with TickerProviderStateMixin {
int _counter = 0;
AnimationController _controller;
int levelClock = 180;

void _incrementCounter() {
setState(() {
_counter++;
});
}

@override
void dispose() {
_controller.dispose();
super.dispose();
}

@override
void initState() {
super.initState();

_controller = AnimationController(vsync: this, duration: Duration(seconds: levelClock) // gameData.levelClock is a user entered number elsewhere in the applciation
);

_controller.forward();
}

@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Countdown(
animation: StepTween(
begin: levelClock, // THIS IS A USER ENTERED NUMBER
end: 0,
).animate(_controller),
),
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}

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

@override
build(BuildContext context) {
Duration clockTimer = Duration(seconds: animation.value);

String timerText = '${clockTimer.inMinutes.remainder(60).toString()}:${clockTimer.inSeconds.remainder(60).toString().padLeft(2, '0')}';

return Column(
children: [
Text(
"$timerText",
style: TextStyle(
fontSize: 110,
color: Theme.of(context).primaryColor,
),
),
),
],
);
}
}

Answer 1

实现这一点的一种方法是在动画中添加一个监听器，就像这样

Countdown(
animation: StepTween(
begin: levelClock,
end: 0,
).animate(_controller)
..addListener(() {
if (_controller.value > (4 / levelClock)) {    //4 = to stop after 5 seconds
_controller.stop();
}
}),
),