父view中添加手势子view不响应的问题解决

// 父类 view
    UIImageView *back = [[ UIImageView alloc ] initWithFrame : CGRectMake ( 0 , 0 , kScreenWidth , kScreenHeight )];
    back. image = [ UIImage imageNamed : @"Default-568h@2x" ];
    back. userInteractionEnabled = YES ;
    [ self . view addSubview :back];
   
    // 父类 view 中的 imageView
    imageView = [[ UIImageView alloc ] initWithFrame : CGRectMake ( 100 , 100 , 100 , 100 )];
    imageView . image = [ UIImage imageNamed : @"Default-568h@2x" ];
    imageView . userInteractionEnabled = YES ;
   
    // 父类 view 中的 label
    label = [[ UILabel alloc ] initWithFrame : CGRectMake ( 100 , 240 , 100 , 100 )];
    label . text = @"label" ;
    label . backgroundColor = [ UIColor grayColor ];
    // 此属性必须打开 , 不然 UITouch 捕获 Label
    label . userInteractionEnabled = YES ;
   
    // 父类 view 中的 button
    button = [ UIButton buttonWithType : UIButtonTypeCustom ];
    [ button setTitle : @"button" forState : UIControlStateNormal ];
    button . frame = CGRectMake ( 100 , 350 , 100 , 100 );
    button . backgroundColor = [ UIColor purpleColor ];
    [ button addTarget : self action : @selector (btn) forControlEvents : UIControlEventTouchUpInside ];

   
    UITapGestureRecognizer *tap = [[ UITapGestureRecognizer alloc ] initWithTarget : self action : @selector (tap:)];
    tap. delegate = self ;

    [back addGestureRecognizer :tap];
    [back addSubview : imageView ];
    [back addSubview : label ];
    [back addSubview : button ];
}
- ( void )btn
{
    NSLog ( @"button" );

}

- ( BOOL )gestureRecognizer:( UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:( UITouch *)touch
{
    // 取消 label 和 imageview 响应手势
    if ([touch. view isKindOfClass :[ UILabel class ]] || touch. view == imageView )
    {
        return NO ;
    }
    return YES ;

}
- ( void )tap:( UITapGestureRecognizer *)tap
{
    NSLog ( @"tap.view = %@" ,tap. view );
}