Question

我将UIVcs添加到另一个UIScrollView。当用户滚动并且当前UIView通过矩形时，它必须改变UIView的背景颜色。如何跟踪子视图是否在定义的矩形内？

- (void) showViews {

    CGRect scrollRect = CGRectMake(0.0f, 44.0f, 704.0f, 704.0f); 

    UIScrollView *aScroll = [[UIScrollView alloc] initWithFrame:scrollRect];
    float yPos = 20.0f;
    //the rectangle to trace intersection
    CGRect intersectRect = CGRectMake(0.0f, 200.0f, 704.0f, 400.0f);

    for (UIView* view in arrayOfViews) {
        CGRect viewRect = CGRectMake(100.0f, yPos, 320.0f, 480.0f); 
        view.frame = viewRect;
        [aScroll addSubView:view];
        yPos = yPos + 340.0f;
        aScroll.contentSize = CGSizeMake(704.0, yPos);
     }


}

Answer 1

CGRectIntersection();可能就是looking。{/ p>

它返回一个CGRect，交集，可以为null（用CGRectIsNull()检查）。如果rects具有相同的大小，并且它们是第二个，则结果应为CGRect，且大小相同。

Answer 2

我在委托方法和属性contentOffset中找到了解决方案。

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {

    for (UIView *view in [[scrollView subviews] copy]) {

        if ((view.frame.origin.y - scrollView.contentOffset.y - self.controllStrip.frame.origin.y - self.controllStrip.frame.size.height) < 0  & 

             ( view.frame.origin.y + view.frame.size.height - scrollView.contentOffset.y - self.controllStrip.frame.origin.y) > 0) {

        view.backgroundColor = [UIColor grayColor];

        }

        else 
            view.backgroundColor = [UIColor greenColor];

    }

}

UIViews是UIScrollView的子视图。如何跟踪子视图是否在定义的矩形内？

2 个答案: