使用下一个上层对象的锚点

Question

目前我正在编写一个事件-UIViewController，其中有三个 UITableViews 显示参与者、感兴趣的人和不能来的人。它们中的每一个都固定在标签下。层次结构如下所示：

descriptionLabel | surePeopleLabel | surePeopleTV | maybePeopleLabel | maybePeopleTV | nopePeopleLabel | nopePeopleTV

现在我只想显示相关的Labels和TableViews。例如，如果没有感兴趣的人，则不应显示关联的元素。

但这会导致一个问题：因为 nopePeopleLabel 的约束设置为从未添加的 maybePeopleTV 的 bottomAnchor，所以程序崩溃。

有谁知道将锚点设置到下一个现有上方对象的（平滑）方法？我添加了我的代码，尽管这不是必需的..

if let sureUsers = surePeopleTV.users, !sureUsers.isEmpty {
    scrollView.addSubview(surePeopleLabel)
    scrollView.addSubview(surePeopleTV)
    let sureTVHeight: CGFloat = CGFloat(sureUsers.count) * 60
    surePeopleLabel.anchor(top: descLabel.bottomAnchor, left: view.leftAnchor, bottom: nil, right: view.rightAnchor, paddingTop: 20, paddingLeft: padding, paddingBottom: 0, paddingRight: padding, width: 0, height: 0)
    surePeopleTV.anchor(top: surePeopleLabel.bottomAnchor, left: view.leftAnchor, bottom: nil, right: view.rightAnchor, paddingTop: 5, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: sureTVHeight)
}

if let maybeUsers = maybePeopleTV.users, !maybeUsers.isEmpty {
    scrollView.addSubview(maybePeopleLabel)
    scrollView.addSubview(maybePeopleTV)
    let maybeTVHeight: CGFloat = CGFloat(maybeUsers.count) * 60
    maybePeopleLabel.anchor(top: surePeopleTV.bottomAnchor, left: view.leftAnchor, bottom: nil, right: view.rightAnchor, paddingTop: 20, paddingLeft: padding, paddingBottom: 0, paddingRight: padding, width: 0, height: 0)
    maybePeopleTV.anchor(top: maybePeopleLabel.bottomAnchor, left: view.leftAnchor, bottom: nil, right: view.rightAnchor, paddingTop: 5, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: maybeTVHeight)
}

if let nopeUsers = nopePeopleTV.users, !nopeUsers.isEmpty {
    scrollView.addSubview(nopePeopleLabel)
    scrollView.addSubview(nopePeopleTV)
    let nopeTVHeight: CGFloat = CGFloat(nopeUsers.count) * 60
    nopePeopleLabel.anchor(top: maybePeopleLabel.bottomAnchor, left: view.leftAnchor, bottom: nil, right: view.rightAnchor, paddingTop: 20, paddingLeft: padding, paddingBottom: 0, paddingRight: padding, width: 0, height: 0)
    nopePeopleTV.anchor(top: nopePeopleLabel.bottomAnchor, left: view.leftAnchor, bottom: scrollView.bottomAnchor, right: view.rightAnchor, paddingTop: 5, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: nopeTVHeight)
}

Answer 1

var lowestObjAnchor: NSLayoutYAxisAnchor = descLabel.bottomAnchor

每当最低锚点发生变化时覆盖此属性，你会没事的。在代码中，它看起来像这样：

if let sureUsers = surePeopleTV.users, !sureUsers.isEmpty {
    scrollView.addSubview(surePeopleLabel)
    scrollView.addSubview(surePeopleTV)
    let sureTVHeight: CGFloat = CGFloat(sureUsers.count) * 60
    surePeopleLabel.anchor(top: lowestObjAnchor, left: view.leftAnchor, bottom: nil, right: view.rightAnchor, paddingTop: 20, paddingLeft: padding, paddingBottom: 0, paddingRight: padding, width: 0, height: 0)
    surePeopleTV.anchor(top: surePeopleLabel.bottomAnchor, left: view.leftAnchor, bottom: nil, right: view.rightAnchor, paddingTop: 5, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: sureTVHeight)

    lowestObjAnchor = surePeopleTV.bottomAnchor
}

Answer 2

你想多了。

不要删除任何对象（标签或 table 视图）。相反，只需将它们的高度（以及中间的间距约束）更改为零。如果每个 label-table 对都在一个超级视图中，然后可以根据需要进行调整，这实际上是最简单的。

或者，使用堆栈视图。它会在您隐藏和显示视图时自动处理视图，为您调整约束。

使用下一个上层对象的锚点

Use anchor from the next upper object

anchor

constraints

ios

autolayout

swift