iOS 倒计时方法

倒计时用到了两种方法：1.NSTimer  2.GCD

设计思路：view上有label和button，label用NSTimer倒计时，button用GCD，点击button同时倒计时，5秒后停止

上代码：

@interface里：

@property (assign,nonatomic)int numer;

@property (strong,nonatomic)NSTimer * timer; 

@property (strong,nonatomic)UILabel * label;

@property (strong,nonatomic)UIButton * btn;

viewDidLoad里：

    self.view.backgroundColor=[UIColor whiteColor];

    self.numer=5;

    UILabel * label=[[UILabel alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];

    label.backgroundColor=[UIColor orangeColor];

    label.textAlignment=NSTextAlignmentCenter;

    label.textColor=[UIColor whiteColor];

    [self.view addSubview:label];

    self.label=label;

    UIButton * btn=[UIButton buttonWithType:UIButtonTypeCustom];

    btn.frame=CGRectMake(100, CGRectGetMaxY(label.frame)+20, 100, 100);

    btn.backgroundColor=[UIColor redColor];

    [btn addTarget:self action:@selector(bbb) forControlEvents:UIControlEventTouchUpInside];

    [btn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];

    [btn setTitle:@"点击" forState:UIControlStateNormal];

    [self.view addSubview:btn];

    self.btn=btn;

button方法和NSTimer方法：

-(void)bbb

{

    self.timer=[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(aaa) userInfo:nil repeats:YES];

    [[NSRunLoop currentRunLoop]addTimer:self.timer forMode:NSRunLoopCommonModes];

    __block int timeout=5; //倒计时时间

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_source_t timers = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);

    dispatch_source_set_timer(timers,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行

    dispatch_source_set_event_handler(timers, ^{

        if(timeout<=0){ //倒计时结束，关闭

            dispatch_source_cancel(timers);

            dispatch_async(dispatch_get_main_queue(), ^{

                //设置界面的按钮显示 根据自己需求设置

                [self.btn setTitle:@"点击" forState:UIControlStateNormal];

                //btn可以点击

                self.btn.userInteractionEnabled=YES;

                self.numer=5;

                [self.btn addTarget:self action:@selector(bbb) forControlEvents:UIControlEventTouchUpInside];

            });

        }else{

            int minutes = timeout / 60;

            int seconds = timeout % 60;

            NSString *strTime = [NSString stringWithFormat:@"%d分%.2d秒",minutes, seconds];

            dispatch_async(dispatch_get_main_queue(), ^{

                //设置界面的按钮显示 根据自己需求设置

                [self.btn setTitle:strTime forState:UIControlStateNormal];

                //btn禁止点击

                self.btn.userInteractionEnabled=NO;

            });

            timeout--;

        }

    });  

    dispatch_resume(timers);

}

-(void)aaa

{

    self.numer--;

    self.label.text=[NSString stringWithFormat:@"%d",self.numer];

    if (self.numer==0) {

        [self.timer invalidate];

        self.label.text=@"没啦";

    }

}

iOS 倒计时方法

原文：http://www.cnblogs.com/tongyuling/p/4647618.html