iOS短信验证码倒计时Button的实现

- (IBAction)sendEvent:(id)sender {
//倒计时时间
__block int timeout=30;

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

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

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

dispatch_source_set_event_handler(_timer, ^{
if(timeout<=0){
//倒计时结束，关闭
dispatch_source_cancel(_timer);

dispatch_async(dispatch_get_main_queue(), ^{
//设置界面的按钮显示 根据自己需求设置
[_countdownButton setTitle:@"发送验证码" forState:UIControlStateNormal];

_countdownButton.backgroundColor = [UIColor orangeColor];
_countdownButton.userInteractionEnabled = YES;
});
}else{
//            int minutes = timeout / 60;

int seconds = timeout % 60;
NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];

dispatch_async(dispatch_get_main_queue(), ^{
//设置界面的按钮显示 根据自己需求设置
NSLog(@"____%@",strTime);

[_countdownButton setTitle:[NSString stringWithFormat:@"%@",strTime] forState:UIControlStateNormal];

_countdownButton.backgroundColor = [UIColor grayColor];
_countdownButton.userInteractionEnabled = NO;
});
timeout--;
}
});
dispatch_resume(_timer);
}