1.- (BOOL)isDescendantOfView:(UIView *)view; // returns YES for self.

使用isDescendantOfView方法来验证，是不是子类关系，不一定是直接子类。

// 弹框bgView

    [self.view addSubview:self.showView];

    // 创建一个轻拍手势 同时绑定了一个事件

    UITapGestureRecognizer *aTapGR = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapGRAction:)];

    aTapGR.delegate = self;

    [self.view addGestureRecognizer:aTapGR];

代理方法，只是阴影背景响应这个手势，中间视图不响应

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch{

   if ([touch.view isDescendantOfView:self.showView]) {

        return NO;

    }

    return YES;

}