短信验证码倒计时

- (void)viewDidLoad {
[super viewDidLoad];
UITextField * tF = [[UITextField alloc]initWithFrame:CGRectMake(10, 50, 150, 30)];
tF.borderStyle = UITextBorderStyleRoundedRect;
tF.placeholder = @"点击发送验证码";
[self.view addSubview:tF];
self.timeButn = [UIButton buttonWithType:UIButtonTypeCustom];//这里的Unbutton类型要设置为Custom，要不然Button上面的数字会一闪一闪。。。亮晶晶
_timeButn.frame = CGRectMake(250, 50, 100, 30);
[_timeButn setTitle:@"获取验证码" forState:UIControlStateNormal];
_timeButn.backgroundColor = [UIColor orangeColor];
[_timeButn addTarget:self action:@selector(timeAction) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:_timeButn];
}

-(void)timeAction{
__block int timeout=60; //倒计时时间
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);
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);
dispatch_async(dispatch_get_main_queue(), ^{
//设置界面的按钮显示 根据自己需求设置
[_timeButn setTitle:@"发送验证码" forState:UIControlStateNormal];
_timeButn.userInteractionEnabled = YES;
});
}else{
int seconds = timeout % 61;
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
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:1];
[_timeButn setTitle:[NSString stringWithFormat:@"%@秒后重新发送",strTime] forState:UIControlStateNormal];
//To do
[UIView commitAnimations];
_timeButn.userInteractionEnabled = NO;
});
timeout--;
}
});
dispatch_resume(_timer);
}