GCD and Timer

The main thread always refreshes the countdown when the page is toggled in the GCD

__block int timeout = 2400; 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); No second execution.

Dispatch_source_set_event_handler (_timer, ^{

if (timeout<=0) {//Countdown end, close

Dispatch_source_cancel (_timer);

Dispatch_async (Dispatch_get_main_queue (), ^{

Set the interface button to display the settings according to your needs

Uialertview * alert = [[Uialertview alloc]initwithtitle:@ "Prompt" message:@ "will be delivered" Delegate:nil Cancelbuttontitle:nil otherbuttontitles:@ "OK", @ "Cancel", nil];

[Alert show];

});

}else{

int minutes = TIMEOUT/60;

NSString * Strtime = [NSString stringwithformat:@ "%d", minutes];

Dispatch_async (Dispatch_get_main_queue (), ^{

Set the interface button to display the settings according to your needs

UIView * Timeview = [[UIView alloc]initwithframe:cgrectmake (10, 140, 150, 150)];

TimeView.layer.cornerRadius = 75;

TimeView.layer.borderWidth = 4;

TimeView.layer.borderColor = [Uicolor colorwithred:0.816 green:0.820 blue:0.824alpha:1.000]. Cgcolor;

Timeview.backgroundcolor = [Uicolor Whitecolor];

[_mainview Addsubview:timeview];

UILabel * Tlabel = [[UILabel alloc]initwithframe:cgrectmake (55, 0, 60, 60)];

Tlabel.text = @ "remaining";

Tlabel.textcolor = [Uicolor blackcolor];

Tlabel.font = [Uifont systemfontofsize:20];

[Timeview Addsubview:tlabel];

UILabel * Mlabel = [[UILabel alloc]initwithframe:cgrectmake (35, 30, 100, 100)];

Mlabel.text = Strtime;

Mlabel.font = [Uifont systemfontofsize:80];

Mlabel.textcolor = [Uicolor Redcolor];

[Timeview Addsubview:mlabel];

UILabel * Llabel = [[UILabel alloc]initwithframe:cgrectmake (55, 100, 60, 60)];

Llabel.text = @ "Minutes";

Llabel.textcolor = [Uicolor Redcolor];

Llabel.font = [Uifont systemfontofsize:20];

[Timeview Addsubview:llabel];

});

timeout--;

}

});

Dispatch_resume (_timer);

#pragrm Mark---nstimer---

1. int Secondscountdown; //Countdown Total Duration
2. Nstimer *countdowntimer;

3. UILabel *labeltext;

2. Create Uilabel add to Current view
4. Labeltext=[[uilabel Alloc]initwithframe:cgrectmake (10, 120, 12 0, 36)]  ;
6. [self. View Addsubview:labeltext];
10. Set the total countdown time
12. Secondscountdown = 60; 60 seconds Countdown
14. Start the countdown.
16. Countdowntimer = [Nstimer scheduledtimerwithtimeinterval:1 target:self selector:@selector ( Timefiremethod) userInfo: nil repeats:YES]; //The method is called once every second after the countdown starts Timefiremethod
20. Set the countdown display time
22. LabelText. text=[nsstring stringWithFormat:@ "%d", Secondscountdown];

2. -(void) timefiremethod{
4. //Countdown-1
6. secondscountdown--;
8. //Modify the countdown tag real content
10. LabelText. text=[nsstring stringWithFormat:@ "%d", Secondscountdown];
12. //When countdown to 0 o'clock, do the required actions, such as verification code expiration cannot be submitted
14. if (secondscountdown==0) {
16. [Countdowntimer invalidate];
18. [LabelText Removefromsuperview];
20. }
22. }

GCD and Timer