Show timer progress on a CircularProgressIndicator in flutter - flutter

Question

I'm using a RestartableTimer (subclass of Timer) as a countdown timer, to "kick people out" of a form after a certain duration.
I would like to display the progress of that timer, and I like the idea of a circular progress slowly filling up.
I'm not showing my code because I don't really have anything to show. I have a completely static progress indicator and a working timer, in a widget (stateful or stateless, whichever works best).
I face two issues and this is where I need help for :
I don't know how to check every x milliseconds for the timer progress. How can I do that? I don't need copy-pasta code, but more of "what object / which direction" should I go for?
The timer progress in ticks is not implemented (NotImplementedException) ; is there any way to have an equivalent somewhere else? That object works really well for me, except for that part.
Am I SOL or is there a way to make it?

Answer 1

There's nothing to be implemented in the getter tick, since RestartableTimer is not periodic. What you want is a much more complex thing, and RestartableTimer is not able to help you with that.
First, you need something to control the progress of the CircularProgressIndicator:
class ProgressController {
static const double smoothnessConstant = 250;
final Duration duration;
final Duration tickPeriod;
Timer _timer;
Timer _periodicTimer;
Stream<void> get progressStream => _progressController.stream;
StreamController<void> _progressController = StreamController<void>.broadcast();
Stream<void> get timeoutStream => _timeoutController.stream;
StreamController<void> _timeoutController = StreamController<void>.broadcast();
double get progress => _progress;
double _progress = 0;
ProgressController({#required this.duration})
: assert(duration != null),
tickPeriod = _calculateTickPeriod(duration);
void start() {
_timer = Timer(duration, () {
_cancelTimers();
_setProgressAndNotify(1);
_timeoutController.add(null);
});
_periodicTimer = Timer.periodic(
tickPeriod,
(Timer timer) {
double progress = _calculateProgress(timer);
_setProgressAndNotify(progress);
},
);
}
void restart() {
_cancelTimers();
start();
}
Future<void> dispose() async {
await _cancelStreams();
_cancelTimers();
}
double _calculateProgress(Timer timer) {
double progress = timer.tick / smoothnessConstant;
if (progress > 1) return 1;
if (progress < 0) return 0;
return progress;
}
void _setProgressAndNotify(double value) {
_progress = value;
_progressController.add(null);
}
Future<void> _cancelStreams() async {
if (!_progressController.isClosed) await _progressController.close();
if (!_timeoutController.isClosed) await _timeoutController.close();
}
void _cancelTimers() {
if (_timer?.isActive == true) _timer.cancel();
if (_periodicTimer?.isActive == true) _periodicTimer.cancel();
}
static Duration _calculateTickPeriod(Duration duration) {
double tickPeriodMs = duration.inMilliseconds / smoothnessConstant;
return Duration(milliseconds: tickPeriodMs.toInt());
}
}
Then you can implement a CircularProgressIndicator that listens to the Streams from ProgressController:
class RestartableCircularProgressIndicator extends StatefulWidget {
final ProgressController controller;
final VoidCallback onTimeout;
RestartableCircularProgressIndicator({
Key key,
#required this.controller,
this.onTimeout,
}) : assert(controller != null),
super(key: key);
#override
_RestartableCircularProgressIndicatorState createState() =>
_RestartableCircularProgressIndicatorState();
}
class _RestartableCircularProgressIndicatorState
extends State<RestartableCircularProgressIndicator> {
ProgressController get controller => widget.controller;
VoidCallback get onTimeout => widget.onTimeout;
#override
void initState() {
super.initState();
controller.progressStream.listen((_) => updateState());
controller.timeoutStream.listen((_) => onTimeout());
}
#override
Widget build(BuildContext context) {
return CircularProgressIndicator(
value: controller.progress,
);
}
void updateState() => setState(() {});
}
You can also pass some of the paramers of CircularProgressIndicator to RestartableCircularProgressIndicator, so you can customize it.
A usage example:
void main() => runApp(MyApp());
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
ProgressController controller;
#override
void initState() {
super.initState();
controller = ProgressController(
duration: Duration(seconds: 5),
);
}
#override
void dispose() {
controller.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
RestartableCircularProgressIndicator(
controller: controller,
onTimeout: () => print('timeout'),
),
RaisedButton(
onPressed: controller.start,
child: Text('Start'),
),
RaisedButton(
onPressed: controller.restart,
child: Text('Restart'),
),
],
),
),
),
);
}
}
I'll convert this into a library someday, but until then I cannot provide the tests and documentation to this code, so you have to study it if you want to understand what's going on here (I'm sorry...).