iOS开发--验证码

第一步，拖两个空间textfiled和button到storyboard上的viewcontroller上。

屏幕快照 2015-08-05 下午11.53.36

第二步，拖线，链接到.h文件中代码如下：

 @property (weak, nonatomic) IBOutlet UIButton *l_timeButton;

第三步，在,m文件中为l_timeButton设置监听器，监听点击事件。

 - (void)viewDidLoad {
    [super viewDidLoad];
    [_l_timeButton addTarget:self action:@selector(startTime) forControlEvents:UIControlEventTouchUpInside];
}

第四步，在方法“startTime”中实现倒计时功能

 -(void)startTime{
    __block int timeout=30; //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
                [_l_timeButton setTitle:@"发送验证码" forState:UIControlStateNormal];
                _l_timeButton.userInteractionEnabled = YES;
            });
        }else{
            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);
                [UIView beginAnimations:nil context:nil];
                [UIView setAnimationDuration:1];
                [_l_timeButton setTitle:[NSString stringWithFormat:@"%@秒后重新发送",strTime] forState:UIControlStateNormal];
                [UIView commitAnimations];
                _l_timeButton.userInteractionEnabled = NO;
            });
            timeout--;
        }
    });
    dispatch_resume(_timer);
}