Countdown in iOS

method One : Use nstimer to achieve (comparison is applicable to send SMS Verification code countdown)

Mainly using Nstimer's Scheduledtimerwithtimeinterval method to execute Changetime method per second

Create a timer to execute Changetime once per second: method

Nstimer * Timer =[nstimer scheduledtimerwithtimeinterval:1.0 target:self selector: @selector (changetime:) userinfo:nil Repeats:yes];

Changetime

-(void) Changetime: (nstimer*) Timer

{

Click to get the btn of the Verification code

UIButton * button = (uibutton*) [Self.view viewwithtag:99];

if (count = = 0) {

Invalidate out after completion

[Timer invalidate];

59s Countdown

Count = 59;

[Button settitle:@ "regain" forstate:uicontrolstatenormal];

button.userinteractionenabled = YES;

Button.alpha = 1;

}

else{

[Button settitle:[nsstring stringwithformat:@ "%d S", Count] forstate:uicontrolstatenormal];

count--;

}

}

method Two : Use GCD to achieve (compare the countdown to use for the merchant to do some sort of activity)

A timer is defined in the. h file to control the time

Countdown timer

dispatch_source_t _timer;

Implemented in. m Files:

Create a timestamp

NSDateFormatter *dateformatter=[[nsdateformatter alloc] init];

Format of time stamps

[Dateformatter setdateformat:@ "Yyyy/mm/dd HH:mm:ss"];

Convert data of type nsstring of the same timestamp format to nsdate type data

NSDate *enddate = [Dateformatter datefromstring:_endtime];

NSDate *startdate = [Dateformatter datefromstring:_starttime];

NSDate *currentdate = [Dateformatter datefromstring:_currenttime];

Calculates the timestamp of the end of the server's current time distance activity

Nstimeinterval timeinterval =[enddate Timeintervalsincedate:currentdate];

Calculates the timestamp of the current time of the server and the start time of the activity

Nstimeinterval Starttonow = [currentdate timeintervalsincedate:startdate];

Countdown time

__block int timeout = timeinterval;

__block int starttimeout = Starttonow;

if (timeout!=0) {

dispatch_queue_t queue = Dispatch_get_global_queue (Dispatch_queue_priority_default, 0);

Parallel queues

Parallel queues can handle multiple tasks at the same time, and can be created with dispatch_queue_create without being able to do so, but generally we use a system-predefined parallel queue, global queue (globally/Concurrent Dispatch Queues). Currently, the system pre-defines four global queues with different operational priorities, which we can obtain through dispatch_get_global_queue.

Dispatch_get_global_queue The first parameter is the priority of the queue and corresponds to four global queues, respectively:

Dispatch_queue_priority_high

Dispatch_queue_priority_default

Dispatch_queue_priority_low

Dispatch_queue_priority_background

The second parameter in Dispatch_get_global_queue is currently reserved, please set it to 0.

Executes per second

_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);

Dispatch_source_set_event_handler (_timer, ^{

Countdown End, close

if (timeout<=0 | | Starttimeout <=0) {

Dispatch_source_cancel (_timer);

_timer = nil;

Run a task in a queue

You can add a new task to a queue at any time, just call Dispatch_async:

Dispatch_async (Dispatch_get_main_queue (), ^{

According to their own needs to design the content to display and show the format, style, etc.

Daylabel.text = @ "0 days";

Hourlabel.text = @ "00:";

Minlabel.text = @ "00:";

Seclabel.text = @ "00";

Label.text = @ "snapping ends!!!" ";

});

}else{

Label.text = @ "Snapping up time remaining:";

int days = (int) (timeout/(3600*24));

if (days==0) {

Daylabel.text = @ "";

}

int hours = (int) ((timeout-days*24*3600)/3600);

int minute = (int) (timeout-days*24*3600-hours*3600)/60;

int second = timeout-days*24*3600-hours*3600-minute*60;

Dispatch_async (Dispatch_get_main_queue (), ^{

if (days==0) {

Daylabel.text = @ "0 days";

}else{

Daylabel.text = [NSString stringwithformat:@ "%d Day", days];

}

if (hours<10) {

Hourlabel.text = [NSString stringwithformat:@ "0%d:", hours];

}else{

Hourlabel.text = [NSString stringwithformat:@ "%d:", hours];

}

if (minute<10) {

Minlabel.text = [NSString stringwithformat:@ "0%d:", minute];

}else{

Minlabel.text = [NSString stringwithformat:@ "%d:", minute];

}

if (second<10) {

Seclabel.text = [NSString stringwithformat:@ "0%d", second];

}else{

Seclabel.text = [NSString stringwithformat:@ "%d", second];

}

});

timeout--;

}

});

Dispatch_resume (_timer);

}

Countdown in iOS