如何在不破坏约束的情况下以编程方式将 UITextField 添加到 UIScrollView？

Question

情况是这样的：我有一个嵌入 UIScrollView 的表单，在表单中有一个部分，用户可以在其中添加 N 个文本字段，所以如果一开始我有这个：

UITextField - textField1
UIButton - Add

当按下 Add 时，我想要这个：

UITextField - textField1
UITextField - textField2
UIButton - Add

虽然添加了文本字段，但无法满足约束条件，因此 UI 中断

那个日志：

[LayoutConstraints] Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. 
    Try this: 
        (1) look at each constraint and try to figure out which you don't expect; 
        (2) find the code that added the unwanted constraint or constraints and fix it. 
(
    "<_UILayoutSupportConstraint:0x1c4c800a0 _UILayoutGuide:0x106ccf4e0.height == 64   (active)>",
    "<_UILayoutSupportConstraint:0x1c4c80050 V:|-(0)-[_UILayoutGuide:0x106ccf4e0]   (active, names: '|':UIView:0x106ccdc10 )>",
    "<_UILayoutSupportConstraint:0x1c4c80ff0 _UILayoutGuide:0x106ccf6d0.height == 0   (active)>",
    "<_UILayoutSupportConstraint:0x1c4c801e0 _UILayoutGuide:0x106ccf6d0.bottom == UIView:0x106ccdc10.bottom   (active)>",
    "<NSLayoutConstraint:0x1c4c80550 UIImageView:0x106cce6c0.height == 5   (active)>",
    "<NSLayoutConstraint:0x1c4c80640 UILabel:0x106ccf070'Completa tu Perfil'.height == 24   (active)>",
    "<NSLayoutConstraint:0x1c0c886b0 form-view.height == 579   (active, names: form-view:0x10ed307c0 )>",
    "<NSLayoutConstraint:0x1c0c8a1e0 V:|-(0)-[form-view]   (active, names: form-view:0x10ed307c0, '|':UIScrollView:0x107a37000 )>",
    "<NSLayoutConstraint:0x1c0c8a320 V:[form-view]-(0)-[profiles-view]   (active, names: profiles-view:0x106ccd430, form-view:0x10ed307c0 )>",
    "<NSLayoutConstraint:0x1c4c80af0 V:[_UILayoutGuide:0x106ccf4e0]-(10)-[UILabel:0x106ccf070'Completa tu Perfil']   (active)>",
    "<NSLayoutConstraint:0x1c4c80cd0 V:[UILabel:0x106ccf070'Completa tu Perfil']-(8)-[UIImageView:0x106cce6c0]   (active)>",
    "<NSLayoutConstraint:0x1c4c80d20 V:[UIImageView:0x106cce6c0]-(0)-[UIScrollView:0x107a37000]   (active)>",
    "<NSLayoutConstraint:0x1c4c80e10 UIImageView:0x106ccddf0.top == profiles-view.top   (active, names: profiles-view:0x106ccd430 )>",
    "<NSLayoutConstraint:0x1c4c80f00 V:[UIImageView:0x106ccddf0]-(0)-[_UILayoutGuide:0x106ccf6d0]   (active)>",
    "<NSLayoutConstraint:0x1c0c8bdb0 'UIView-Encapsulated-Layout-Height' UIView:0x106ccdc10.height == 667   (active)>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x1c0c886b0 form-view.height == 579   (active, names: form-view:0x10ed307c0 )>

因此，由于高度限制被打破，AutoLayout 会按照允许视图以这种方式打破的边距限制排列元素。

也就是说，我添加约束的方式是这样的：

func addModelButtonAction(_ sender: Any) { // an IBAction 
    addButton.isHighlighted = false
    let last = modelTextFields.last!
    let textField = last.createCopy() // extension method for creating a copy of the last textField
    modelTextFieldsView.insertSubview(textField, belowSubview: last)
    let growth = last.frame.height + 8 // the 8 represents the top spacing between textFields
    formViewHeight.constant += growth // increasing height of the view where the form is embeded
    modelTextFieldsHeight.constant += growth // increasing height of the view where the textFields are embeded
    UIView.animate(withDuration: 0.5) {
        self.view.layoutIfNeeded()
        textField.frame.origin.y += growth // moving new textField below the previous one
    }

    modelTextFields.append(textField) // array of UITextField to keep track of the textFields in screen
}

以及视图的对齐矩形：

以及视图的层次结构：

我该怎么做才能使这项工作按预期进行？感谢您在这方面的帮助，因为我一直试图解决这个问题，但没有成功。

提前致谢！

Answer 1

您有几个选项可以解决此布局问题：

就个人而言，我可能会尝试将这些视图嵌入 UIStackView。堆栈视图将为您管理垂直布局，允许您根据需要插入和删除子视图。 UIStackView 如果您使用情节提要，则在 Interface Builder 中使用起来特别容易。

或者，您可以为此布局使用 UITableView；它会代表你管理垂直流，从你身上抽象出很多令人头疼的布局问题，尽管你需要自己管理数据源和单元格。

通过仔细管理不同约束的优先级，允许在布局更改时破坏某些约束，您可以在没有这些条件的情况下使此布局正常工作，但这可能是一件乏味的工作。

如何在不破坏约束的情况下以编程方式将 UITextField 添加到 UIScrollView？

How to add UITextField programmatically to UIScrollView without breaking constraints?

ios

ios-autolayout