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  • gcd倒计时

    @interface ViewController ()
    {
        dispatch_source_t _timer;
    }
    @property (weak, nonatomic) IBOutlet UILabel *timeLab;
    @end
    
    @implementation ViewController
    
    - (void)viewDidLoad {
        [super viewDidLoad];
        // Do any additional setup after loading the view, typically from a nib.
    }
    
    
    - (void)didReceiveMemoryWarning {
        [super didReceiveMemoryWarning];
        // Dispose of any resources that can be recreated.
    }
    
    - (IBAction)alertBtnClick:(id)sender {
        
        
        UIButton *_codeBtn =(UIButton *)sender;
        
        __block int timeout=59; //倒计时时间
        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
        //typedispatch源可处理的事件
        _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
                    _codeBtn.hidden = NO;
                    _timeLab.hidden = YES;
                    [_codeBtn setTitle:@"获取验证码" forState:UIControlStateNormal];
                });
            }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);
                    _timeLab.hidden = NO;
                    _codeBtn.hidden = YES;
                    _timeLab.text = [NSString stringWithFormat:@"%@秒后重新获取",strTime];
                });
                timeout--;
            }
        });
        //立即执行
        dispatch_resume(_timer);
    
        
        
        
        
    }
    -(void)viewWillDisappear:(BOOL)animated{
        
        
        [super viewWillDisappear:animated];
        if(_timer){
            dispatch_source_cancel(_timer);
        }
    }
    
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  • 原文地址:https://www.cnblogs.com/hualuoshuijia/p/7285005.html
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