在app 注册或者登录 需要验证码的地方、为了避免短时间内刷验证码、往往会加上一层验证。

 

倒计时结束后、可以重新获取！

 

代码实现如下：

 

// _CountdownTime 倒计时总时间；

//_timer 定时器

- (void)startTime:(UIButton *)VerificationCodeButton {    __block NSInteger timeout = [_CountdownTime integerValue];        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    _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);    dispatch_source_set_event_handler(_timer, ^{        if(timeout<=0){            dispatch_source_cancel(_timer);            dispatch_async(dispatch_get_main_queue(), ^{                [VerificationCodeButton setTitle:@"重新获取" forState:UIControlStateNormal];                VerificationCodeButton.userInteractionEnabled = YES;                VerificationCodeButton.alpha = 1.0;                VerificationCodeButton.backgroundColor = [UIColor whiteColor];            });        } else {            NSString *strTime = [NSString stringWithFormat:@"%lds", (long)timeout];            dispatch_async(dispatch_get_main_queue(), ^{                [VerificationCodeButton setTitle:strTime forState:UIControlStateNormal];                VerificationCodeButton.userInteractionEnabled = NO;                VerificationCodeButton.backgroundColor = [UIColor lightTextColor];            });            timeout--;        }    });    dispatch_resume(_timer);}