限时抢购，倒计时，定时器

摘要: 做商城，支付，一元夺宝类的APP 通常会遇见限时抢购问题，那么就由老司机带你来体验限时抢购。



@interface ViewController ()

{

dispatch_source_t _timer;

}

@property (nonatomic,strong)UILabel *hourLabel;

@property (nonatomic,strong)UILabel *minuteLabel;

@property (nonatomic,strong)UILabel *secondLabel;

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

[self createTimeLabel];

// 后台传给你的时间参数（注意日期的格式）

[self CountdownWithTimeString:@"2016-7-16 12:25:00"];

}

- (void)createTimeLabel{

_hourLabel = [[UILabel alloc]initWithFrame:CGRectMake(150, 150, 50, 20)];

[self.view addSubview:_hourLabel];

_minuteLabel = [[UILabel alloc]initWithFrame:CGRectMake(200, 150, 50, 20)];

[self.view addSubview:_minuteLabel];

_secondLabel = [[UILabel alloc]initWithFrame:CGRectMake(250, 150, 50, 20)];

[self.view addSubview:_secondLabel];

}

- (void)CountdownWithTimeString:(NSString *)string{

NSDateFormatter *dateFormatter=[[NSDateFormatter alloc] init];

[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

NSDate *endDate = [dateFormatter dateFromString:string];

NSDate *endDate_tomorrow = [[NSDate alloc] initWithTimeIntervalSinceReferenceDate:([endDate timeIntervalSinceReferenceDate])];

NSDate *startDate = [NSDate date];

NSTimeInterval timeInterval =[endDate_tomorrow timeIntervalSinceDate:startDate];

if (_timer==nil) {

__block int timeout = timeInterval; //倒计时时间

if (timeout!=0) {

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

_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); //每秒执行

dispatch_source_set_event_handler(_timer, ^{

if(timeout<=0){ //倒计时结束，关闭

dispatch_source_cancel(_timer);

_timer = nil;

dispatch_async(dispatch_get_main_queue(), ^{

self.dayLabel.text = @"";

self.hourLabel.text = @"00";

self.minuteLabel.text = @"00";

self.secondLabel.text = @"00";

});

}else{

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

int hours1 = (int)((timeout-days)/3600);

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 (hours1<10) {

self.hourLabel.text = [NSString stringWithFormat:@"0%d",hours1];

}else{

self.hourLabel.text = [NSString stringWithFormat:@"%d",hours1];

}

if (minute<10) {

self.minuteLabel.text = [NSString stringWithFormat:@"0%d",minute];

}else{

self.minuteLabel.text = [NSString stringWithFormat:@"%d",minute];

}

if (second<10) {

self.secondLabel.text = [NSString stringWithFormat:@"0%d",second];

}else{

self.secondLabel.text = [NSString stringWithFormat:@"%d",second];

}

});

timeout--;

}

});

dispatch_resume(_timer);

}

}

}