Countdown in text flutter - dart

Question

We need to create a 5 minute countdown text object in Flutter, once the countdown reaches zero then we need to launch a new screen. here is the current code:
Container(
margin: EdgeInsets.only(left: 0.0,top: 60.0, bottom: 50.0, right:0.0),
child: Text(
'5:00', style: new TextStyle( color: Colors.white, fontWeight: FontWeight.bold, fontSize: 100.0 ))
,
),

Answer 1

I usually don't post just sample code, but I was in the mood of coding a bit in flutter. So here's my quick suggestion on how you can implement this:
class _MyHomePageState extends State<MyHomePage> {
TickViewModel _viewModel;
int _seconds;
StreamSubscription<int> _tickSubscription;
#override
void initState() {
super.initState();
_viewModel = TickViewModel();
_tickSubscription = _viewModel._tickStream.listen((newTime) {
if (newTime == 0) {
//TODO: DO THE SCREEN CHANGE HERE;
}
setState(() {
_seconds = newTime;
});
});
}
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text("My Flutter App"),
backgroundColor: Colors.red,
),
body: Text(_computeTime()));
}
String _computeTime() {
if (_seconds == null) {
return "-";
}
String minutes = "${_seconds ~/ 60}".padLeft(2, "0");
String seconds = "${_seconds % 60}".padLeft(2, "0");
return "$minutes:$seconds";
}
#override
void dispose() {
//We cleanup the stuffs here
_tickSubscription.cancel();
_viewModel.destroy();
super.dispose();
}
}
class TickViewModel {
static const int _fiveMinutes = 5 * 60;
StreamController<int> _ticker;
Stream<int> get _tickStream => _ticker.stream;
Timer _timer;
final int seconds;
int _internalSeconds;
TickViewModel({this.seconds = _fiveMinutes}) : _internalSeconds = seconds {
_ticker = StreamController(onListen: () {
//start timer only when we have a subscriber
_startTimer();
}, onCancel: () {
_timer.cancel();
});
}
void _startTimer() {
//start timer to tick every 1 second
_timer = Timer.periodic(Duration(seconds: 1), (timer) {
_internalSeconds -= 1;
if (_internalSeconds < 0) {
_timer.cancel();
} else {
_ticker.add(_internalSeconds);
}
});
}
void destroy() {
_ticker.close();
_timer.cancel();
}
}