Update iOS Cordova WebView when app is in brackground - ios

Question

I'm building an app for iOS and Android. The app has a JavaScript counter, which updates the time every seconds. When I press the home button in Android and the I come back, the counter is right, it updates when the app is on background, but the iOS doesn't.
Is there a way to make the iOS update the WebView on background?
Sample JS code to update the counter:
setInterval(){
$('#div').html(counter);
counter -= 1;
}, 1000);

Answer 1

I'm afraid tt's not really possible to this in background mode on iOS.
As #Hanh-le mentioned iOS will stop (pause) your app in about 10 seconds from the moment you send it to the background.
Only some native functionality (service) can keep it running (like music playing, bluetooth running in the background, etc).
This services can actually call javascript otherwise Javascript will be stopped.
EDIT (added your function of setinterval) if you set up your interval like this:
window.localStorage.setItem(
'counterInterval',
setInterval({
$('#div').html(counter);
counter -= 1;
}, 1000);
);
You could save the timestamp on the onPause() event and also clear your interval
function onPause() {
clearInterval(window.localStorage.getItem('counterInterval');
window.localStorage.setItem('pauseTime', new Date());
}
and then check for the elapsed time on onResume() event and then update your counter:
function onResume() {
var resumeTime = new Date(),
pauseTime = window.localStorage.getItem('pauseTime'),
elapsedTime = (resumeTime.getTime() - pauseTime.getTime()) / 1000;
//you can round elapsedTime if you'd like
elapsedTime = Math.round(elapsedTime);
//correct the counter
$('#div').html(counter);
counter -= elapsedTime;
//set interval again until the next `Pause` event
window.localStorage.setItem(
'counterInterval',
setInterval({
$('#div').html(counter);
counter -= 1;
}, 1000);
);
}
This would save resources on background mode anyway...