Question

在项目中，我基于约束创建了分页滚动视图。大多数视图是在xib中设置的（UIView的SlideViewController和SlideView子类将添加到滚动视图中）。 SlideViewController包含UIScrollView和UIView作为内容视图，该视图绑定到具有约束的滚动视图。在xib中，这是简单的设置。当我尝试向内容视图添加多个SlideView时出现问题。当然我要添加约束。首先，它会向警告Unable to simultaneously satisfy constraints.发出详细信息：

"<NSLayoutConstraint:0x600001806b70 H:|-(0)-[UIView:0x7ffac0d0cb40]   (active, names: '|':UIScrollView:0x7ffac1842600 )>",
    "<NSLayoutConstraint:0x600001806d00 UIView:0x7ffac0d0cb40.centerX == UIScrollView:0x7ffac1842600.centerX   (active)>",
    "<NSLayoutConstraint:0x600001805400 UIScrollView:0x7ffac1842600.trailing == UILayoutGuide:0x6000002308c0'UIViewSafeAreaLayoutGuide'.trailing   (active)>",
    "<NSLayoutConstraint:0x6000018058b0 UIScrollView:0x7ffac1842600.leading == UILayoutGuide:0x6000002308c0'UIViewSafeAreaLayoutGuide'.leading   (active)>",
    "<NSLayoutConstraint:0x6000018065d0 H:|-(0)-[PagingScrollView.SlideView:0x7ffac380be10](LTR)   (active, names: '|':UIView:0x7ffac0d0cb40 )>",
    "<NSLayoutConstraint:0x600001806670 PagingScrollView.SlideView:0x7ffac380be10.width == UIScrollView:0x7ffac1842600.width   (active)>",
    "<NSLayoutConstraint:0x600001806760 H:[PagingScrollView.SlideView:0x7ffac380be10]-(0)-[PagingScrollView.SlideView:0x7ffac3814d10](LTR)   (active)>",
    "<NSLayoutConstraint:0x600001806ad0 PagingScrollView.SlideView:0x7ffac3814d10.width == UIScrollView:0x7ffac1842600.width   (active)>",
    "<NSLayoutConstraint:0x600001806d50 H:[PagingScrollView.SlideView:0x7ffac3814d10]-(0)-[PagingScrollView.SlideView:0x7ffac3805d20](LTR)   (active)>",
    "<NSLayoutConstraint:0x600001806e90 PagingScrollView.SlideView:0x7ffac3805d20.width == UIScrollView:0x7ffac1842600.width   (active)>",
    "<NSLayoutConstraint:0x6000018070c0 H:[PagingScrollView.SlideView:0x7ffac3805d20]-(0)-[PagingScrollView.SlideView:0x7ffac3801b10](LTR)   (active)>",
    "<NSLayoutConstraint:0x600001807200 PagingScrollView.SlideView:0x7ffac3801b10.width == UIScrollView:0x7ffac1842600.width   (active)>",
    "<NSLayoutConstraint:0x6000018072f0 PagingScrollView.SlideView:0x7ffac3801b10.right == UIView:0x7ffac0d0cb40.right   (active)>",
    "<NSLayoutConstraint:0x600001818ff0 'UIView-Encapsulated-Layout-Width' UIView:0x7ffac0d0fba0.width == 414   (active)>",
    "<NSLayoutConstraint:0x600001804460 'UIViewSafeAreaLayoutGuide-left' H:|-(0)-[UILayoutGuide:0x6000002308c0'UIViewSafeAreaLayoutGuide'](LTR)   (active, names: '|':UIView:0x7ffac0d0fba0 )>",
    "<NSLayoutConstraint:0x600001805130 'UIViewSafeAreaLayoutGuide-right' H:[UILayoutGuide:0x6000002308c0'UIViewSafeAreaLayoutGuide']-(0)-|(LTR)   (active, names: '|':UIView:0x7ffac0d0fba0 )>"

它根本不会滚动。仅显示最后一个SlideView。看来contentView并未根据约束调整大小。

以下代码负责将每个SlideView添加到ScrollView（精确地添加到内容视图）：

private func setup() {
        var prevLeftAnchor = contentView.leftAnchor;

        for i in 0 ..< slides.count {
            slides[i].translatesAutoresizingMaskIntoConstraints = false
            contentView.addSubview(slides[i])

            slides[i].leftAnchor.constraint(equalTo: prevLeftAnchor).isActive = true
            slides[i].topAnchor.constraint(equalTo: contentView.topAnchor).isActive = true
            slides[i].widthAnchor.constraint(equalTo: scrollView.widthAnchor).isActive = true
            slides[i].heightAnchor.constraint(equalTo: scrollView.heightAnchor).isActive = true
            prevLeftAnchor = slides[i].rightAnchor;
        }

        slides.last?.rightAnchor.constraint(equalTo: contentView.rightAnchor).isActive = true;
}

几个小时后，我陷入困境，看不到问题出在哪里。感谢您的答复。

您可以查看github中的简单项目 https://github.com/sumofighter666/PageScroller

Answer 1

在您的SlideViewController.xib中，您对CenterX有一个Content View约束...

删除该约束，您应该可以滚动。

请注意，您还具有两个 Leading约束。由于它们是相同的，因此不会有任何影响，但为清楚起见，最好删除其中之一。

分页滚动视图约束布局问题

1 个答案: