1  __block int time = 60;
 2         __block UIButton *verifybutton = _GetverificationBtn;
 3         verifybutton.enabled = NO;
 4         dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
 5         dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
 6         dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行
 7         dispatch_source_set_event_handler(_timer, ^{
 8             if(time<=0){ //倒计时结束，关闭
 9                 dispatch_source_cancel(_timer);
10                 dispatch_async(dispatch_get_main_queue(), ^{
11                     //设置界面的按钮显示 根据自己需求设置
12                     [verifybutton setTitle:@"获取验证码" forState:UIControlStateNormal];
13                     verifybutton.enabled = YES;
14                 });
15             }else{
16                 dispatch_async(dispatch_get_main_queue(), ^{
17                     //设置界面的按钮显示 根据自己需求设置
18                     verifybutton.backgroundColor = [UIColor grayColor];
19                     NSString *strTime = [NSString stringWithFormat:@"获取验证码(%d)",time];
20                     [verifybutton setTitle:strTime forState:UIControlStateNormal];
21                     verifybutton.titleLabel.textColor = [UIColor whiteColor];
22                 });
23                 time--;
24             }
25         });
26         dispatch_resume(_timer);