Today, a friend asked me that the iOS implementation of the timer switch to the background cannot be executed, and the countdown timer does not execute. So I searched for a lot of information. In the end practice solved the problem, I pasted the core code below:
__block int timeout= 60 ; // Countdown time
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
dispatch_source_set_timer (_timer, dispatch_walltime ( NULL , 0 ), 1.0 * NSEC_PER_SEC , 0 ); // execute every second
dispatch_source_set_event_handler(_timer, ^{
if (timeout<= 0 ){ // Countdown ends, close
dispatch_source_cancel(_timer);
dispatch_async(dispatch_get_main_queue(), ^{
// The button display of the setting interface is set according to your own needs
// [ _sendButton setTitle : @" Send verification code " forState : UIControlStateNormal ];
// _sendButton.userInteractionEnabled = YES;
});
}else{
int seconds = timeout % 60;
NSString *strTime = [NSStringstringWithFormat:@"%.2d", seconds];
dispatch_async(dispatch_get_main_queue(), ^{
// The button display of the setting interface is set according to your own needs
//[ _sendButton setTitle :[ NSString stringWithFormat : @" Resend (%@)" ,strTime] forState : UIControlStateNormal ];
//_sendButton.userInteractionEnabled = NO;
});
timeout--;
}
});
dispatch_resume(_timer);
}