How to handle onPause/onResume in Flutter App?
I'm new to Dart/Flutter and would like to build a simple app where a LinearProgressBar gets updated every second.
Without getting too much into the actual code, I have the following setup working.
- A function that calculates the progress, based on passed time.
- A LinearProgressBar showing the progress.
- A periodic Timer recalculating the progress and updating the progress bar every second.
- I debugprint 'tick' every time, the recalculation is done.
Everything is working as expected with one exception. The 'tick' keeps getting printed when I move the app in the background on my Android device.
On native Android, I would cancel my periodic Timer when the 'onPause' event is triggered.
Is there something similar in Flutter? All I could find was 'initState' and 'dispose'. Dispose, however, does not get called when moving the app to background.
I don't want the timer to keep ticking in the background.
On my research, I found this Stack Overflow question onresume-and-onpause-for-widgets-on-flutter. It's answer suggests using TickerProviderStateMixin.
I used it the following way.
class _BarItemState extends State<BarItem> with SingleTickerProviderStateMixin {
Ticker ticker;
num progress = 1.0;
@override
void initState() {
super.initState();
ticker = createTicker((duration) => setState(() {
debugPrint('tick');
progress = duration.inSeconds / 30;
}))
..start();
}
// other stuff omitted
}
It is working, but I'm still not satisfied.
The reason is, that the ticker callback is getting now called every few milliseconds instead of once a second. This seems to me like a waste of resources (I don't need a smooth animation), ... am I overcomplicating things?
Even if it seems that I don't need it for my use case, I still would like to know:
How to handle the onPause/onResume events on my own?
