iOS开发--验证码

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

第二步，拖线，链接到.h文件中代码如下：

1	@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。

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- (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

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-(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); }

一个验证码倒计时的功能就写好了