iOS 倒计时 三种方式

#define TIMECOUNT 60

@interface ViewController ()

@property (strong, nonatomic) IBOutlet UIButton *firstBtn;

@property (strong, nonatomic) IBOutlet UIButton *secondBtn;

@property (strong, nonatomic) IBOutlet UIButton *thirdBtn;

@property (assign, nonatomic) int count;

@property (nonatomic, strong) NSTimer *timer;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

    self.count = TIMECOUNT;

}

- (void)viewDidDisappear:(BOOL)animated {

    //页面消失的时候暂停定时器，防止出现循环引用，导致内存泄漏

    [self.timer invalidate];

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

//------------***第一种方法***------------

#pragma mark 线程Thread方式实现

- (IBAction)firstBtnAction:(id)sender {

    //创建一个后台线程执行计时操作

    [self performSelectorInBackground:@selector(timerThread) withObject:nil];

}

- (void)timerThread {

    for (int i = TIMECOUNT; i >= 0 ; i--) {

        self.count--;

        //切换到主线程中更新UI

        [self performSelectorOnMainThread:@selector(updateFirstBtn) withObject:nil waitUntilDone:YES];

        sleep(1);

    }

}

//更新UI

- (void)updateFirstBtn {

    NSString *str = nil;

    if (self.count == 0) {

        str = [NSString stringWithFormat:@"点击获取验证码"];

        self.firstBtn.userInteractionEnabled = YES;

    } else {

        str = [NSString stringWithFormat:@"%d秒后重新获取",self.count];

        self.firstBtn.userInteractionEnabled = NO;

    }

    [self.firstBtn setTitle:str forState:UIControlStateNormal];

}

//------------***第二种方法***------------

//NSTimer方式实现 (此种方式实现的时候，要注意Timer invalidate的时机，防止循环引用)

#pragma mark NSTimer实现

- (IBAction)secondBtnAction:(id)sender {

    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(handleTimer) userInfo:nil repeats:YES];

}

//定时操作，更新UI

- (void)handleTimer {

    if (self.count == 0) {

        self.secondBtn.userInteractionEnabled = YES;

        [self.secondBtn setTitle:[NSString stringWithFormat:@"点击获取验证码"] forState:UIControlStateNormal];

        self.count = TIMECOUNT;

        [self.timer invalidate];

    } else {

        self.secondBtn.userInteractionEnabled = NO;

        [self.secondBtn setTitle:[NSString stringWithFormat:@"%d秒后重新获取",self.count] forState:UIControlStateNormal];

    }

    self.count--;

}

//------------***第三种方法***------------

/**

 *  1、获取或者创建一个队列，一般情况下获取一个全局的队列

 *  2、创建一个定时器模式的事件源

 *  3、设置定时器的响应间隔

 *  4、设置定时器事件源的响应回调，当定时事件发生时，执行此回调

 *  5、启动定时器事件

 *  6、取消定时器dispatch源，【必须】

 *

 */

#pragma mark GCD实现

- (IBAction)thirdBtnAction:(id)sender {

    __block NSInteger second = TIMECOUNT;

    //(1)

    dispatch_queue_t quene = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    //(2)

    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, quene);

    //(3)

    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC, 0 * NSEC_PER_SEC);

    //(4)

    dispatch_source_set_event_handler(timer, ^{

        dispatch_async(dispatch_get_main_queue(), ^{

            if (second == 0) {

                self.thirdBtn.userInteractionEnabled = YES;

                [self.thirdBtn setTitle:[NSString stringWithFormat:@"点击获取验证码"] forState:UIControlStateNormal];

                second = TIMECOUNT;

                //(6)

                dispatch_cancel(timer);

            } else {

                self.thirdBtn.userInteractionEnabled = NO;

                [self.thirdBtn setTitle:[NSString stringWithFormat:@"%ld秒后重新获取",second] forState:UIControlStateNormal];

                second--;

            }

        });

    });

    //(5)

    dispatch_resume(timer);

}

@end

转载链接：https://www.jianshu.com/p/4ec7faeb0cd9