发送验证码倒计时

//倒计时
-(void)startTime{
    
    //重新发送验证码
    NSDictionary *dic = @{@"mobileNumber":self.phoneNumber};
    [HttpTool1 post:GetRegVerificationCodeUrl params:dic success:^(id mydata) {
        NSLog(@"成功－－－－");
        NSString *str = [[NSString alloc] initWithData:mydata encoding:NSUTF8StringEncoding];
        NSLog(@"%@",str);
        if([str isEqualToString:@"0001"]){
            [MBProgressHUD showError:@"发送失败"];
        }
    }
    failure:^(NSError *error) {
        NSLog(@"失败－－－－－");
    }];

    
    __block int timeout=60; //倒计时时间
    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); //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
                [_againLabel setTitle:@"发送验证码" forState:UIControlStateNormal];
                _againLabel.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
                [_againLabel setTitle:[NSString stringWithFormat:@"重新发送(%@)",strTime] forState:UIControlStateNormal];
                _againLabel.userInteractionEnabled = NO;
                
            });
            timeout--;
            
        }
    });
   dispatch_resume(_timer);
    

}

发送验证码倒计时

原文：http://www.cnblogs.com/dewengood/p/4728306.html