NSTimer Keep counting after app is closed in iPhone

问题:

I have a timer that have to count up to 8 hours (28800 second) after that it should be released

im wondering how to keep the timer running at the background and/or when application is closed?

this is the NSTimer :

stopWatchTimer = [NSTimer scheduledTimerWithTimeInterval:1.0                                                       target:self                                                     selector:@selector(updateTimer)                                                     userInfo:nil                                                      repeats:YES]; 

and this is my condition :

 counter++;  if (counter >= 28800) {     [stopWatchTimer invalidate];     counter =0;      timeLabel.text = @"Time Out"; } 

回答1:

You can't - once your app is closed then it's not running anymore so the timer won't be running either.

Take a look at local notifications?

回答2:

When application goes in background, In application delegate method add current counter value and current time in nsuserdefault.

Now when application becomes active before that will called so in that method get total seconds application was in background ie (current time of application) - (time when application went background which is stored in nsuserdefault) calculate in seconds

 if((seconds calculated) > (28800 - (current counter value stored in nsuserdefault)))  {     // stop timer as it has gone beyond eight hours  }   else  {   // continue task  } 

文章来源: NSTimer Keep counting after app is closed in iPhone