ios - invalidate NSTimer inside dispatch_async -

i creating game, , inside game need time counter.

i works great when scroll map stops , when finish scrolling start again. fix dispatch_async. here code

dispatch_async(dispatch_get_global_queue(dispatch_queue_priority_default, 0), ^{                  timer = [nstimer scheduledtimerwithtimeinterval:1 target:self  selector:@selector(timenext) userinfo:nil repeats:no];                  [[nsrunloop currentrunloop] addtimer:timer formode:nsdefaultrunloopmode];                  [[nsrunloop currentrunloop] run];              }); 

timer:

__block nstimer *timer; 

but if app goes background need stop times (and when active starts again).

with way can scroll map , timer works try:

- (void)timenext {     [timer invalidate];     } 

and didin't work. knows how stop it? or other idea accomplish task?

don't create timer on global queue's thread , start run loop on thread.

just create timer on main thread (main run loop), , add tracking run loop mode. timer can added multiple run loop modes.

timer = [nstimer scheduledtimerwithtimeinterval:1 target:self  selector:@selector(timenext) userinfo:nil repeats:no]; [[nsrunloop currentrunloop] addtimer:timer formode:uitrackingrunloopmode];