UIScrollViews 和快速锚点

Question

我在设置滚动视图和实际向下滚动时遇到问题。我用一些文本字段填充滚动视图并使用锚点（topanchor、leftanchor...）将它们定位在滚动视图内。即使我将滚动视图高度设置为 1000，它实际上也不会移动，它会继续显示相同的项目，滚动指示器确实会下降，但内容本身不会，我已经将滚动视图设置为启用滚动，并委托给自己。

我认为问题可能出在锚点上，但是我将如何在滚动视图中排列我的项目，任何建议都会得到极大的赞赏。

编辑：下面的代码表示应用于滚动视图（ inputContainer ）的锚点，img 对应于 UIImageView，而 mainContainer 对应于包含 img 和 inputContainer 的 UIView。

inputContainer.topAnchor.constraintEqualToAnchor( img.bottomAnchor ).active = true
inputContainer.leftAnchor.constraintEqualToAnchor( mainContainer.leftAnchor ).active = true

inputContainer.widthAnchor.constraintEqualToAnchor( mainContainer.widthAnchor ).active = true

inputContainerBottomConstraint = inputContainer.bottomAnchor.constraintEqualToAnchor( cancelButton.topAnchor )
inputContainerBottomConstraint?.active = true

编辑：这就是代码的样子：

class SView : UIView, UITextFieldDelegate, UIScrollViewDelegate {

let mainContainer : UIView = {
    let v = UIView()
    v.backgroundColor = .whiteColor()
    v.layer.cornerRadius = 8
    v.layer.masksToBounds = true
    v.translatesAutoresizingMaskIntoConstraints = false
    return v
}()

let Img : UIImageView = {
    let img = UIImageView()
    img.image = UIImage(named: "noImage")
    img.backgroundColor = .blueColor()
    img.translatesAutoresizingMaskIntoConstraints = false
    img.contentMode = .ScaleAspectFill
    img.clipsToBounds = true
    return img
}()

let inputContainer : UIScrollView = {
    let ic = UIScrollView()
    ic.backgroundColor = .whiteColor()
    ic.translatesAutoresizingMaskIntoConstraints = false
    return ic
}()

let datePickerTextField : UITextField = {
    let tf = UITextField()
    tf.placeholder = "Fecha"
    tf.textAlignment = .Center
    tf.translatesAutoresizingMaskIntoConstraints = false
    return tf
}()

let tagsTextField : UITextField = {
    let tf = UITextField()
    tf.placeholder = "Tags"
    tf.textAlignment = .Center
    tf.clearButtonMode = .Always
    tf.translatesAutoresizingMaskIntoConstraints = false
    return tf
}()

lazy var cancelButton : UIButton = {
    let button = UIButton()
    button.backgroundColor = UIColor.rgb(255, green: 65, blue: 65, alpha: 1)
    button.setTitle("Cancelar", forState: .Normal)
    button.tintColor = .whiteColor()
    button.translatesAutoresizingMaskIntoConstraints = false

    button.addTarget( self , action: #selector(handleCancelButtonPressed), forControlEvents: .TouchUpInside)

    return button
}()

lazy var publicarButton : UIButton = {
    let button = UIButton()
    button.backgroundColor = UIColor.rgb(0 , green: 204, blue: 102, alpha: 1)
    button.setTitle("Publicar", forState: .Normal)
    button.tintColor = .whiteColor()
    button.translatesAutoresizingMaskIntoConstraints = false

    button.addTarget( self , action: #selector(handlePublicarButtonPressed), forControlEvents: .TouchUpInside)

    return button
}()


override init(frame: CGRect)
{
    super.init(frame: frame)

    inputContainer.delegate = self


    datePickerTextField.delegate = self

    tagsTextField.delegate = self

    setupMainContainer()
    setupImg()
    setupButtons()
    setupInputContainer()

}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

func setupMainContainer ()
{
    addSubview(mainContainer)

    mainContainer.centerXAnchor.constraintEqualToAnchor( centerXAnchor ).active = true
    mainContainer.centerYAnchor.constraintEqualToAnchor( centerYAnchor ).active = true

    mainContainer.widthAnchor.constraintEqualToAnchor( widthAnchor ).active = true
    mainContainer.heightAnchor.constraintEqualToAnchor( heightAnchor )
}

func setupImg ()
{
    mainContainer.addSubview(Img)

    Img.topAnchor.constraintEqualToAnchor( mainContainer.topAnchor ).active = true
    Img.leftAnchor.constraintEqualToAnchor( mainContainer.leftAnchor ).active = true

    Img.widthAnchor.constraintEqualToAnchor( mainContainer.widthAnchor ).active = true
    Img.heightAnchor.constraintEqualToAnchor( mainContainer.heightAnchor , multiplier: 0.3).active = true
}

var inputContainerBottomConstraint : NSLayoutConstraint?

func setupInputContainer ()
{
    mainContainer.addSubview(inputContainer)

    inputContainer.topAnchor.constraintEqualToAnchor( Img.bottomAnchor ).active = true
    inputContainer.leftAnchor.constraintEqualToAnchor( mainContainer.leftAnchor ).active = true
    inputContainer.rightAnchor.constraintEqualToAnchor( mainContainer.rightAnchor ).active = true
    inputContainerBottomConstraint = inputContainer.bottomAnchor.constraintEqualToAnchor( cancelButton.topAnchor )
    inputContainerBottomConstraint?.active = true



    inputContainer.addSubview( datePickerTextField )
    inputContainer.addSubview( tagsTextField )




    datePickerTextField.topAnchor.constraintEqualToAnchor( inputContainer.topAnchor ).active = true
    datePickerTextField.centerXAnchor.constraintEqualToAnchor( inputContainer.centerXAnchor ).active = true

    datePickerTextField.widthAnchor.constraintEqualToAnchor( inputContainer.widthAnchor ).active = true
    datePickerTextField.heightAnchor.constraintEqualToAnchor( inputContainer.heightAnchor, multiplier: 0.2 ).active = true


    tagsTextField.bottomAnchor.constraintEqualToAnchor( inputContainer.bottomAnchor ).active = true
    tagsTextField.centerXAnchor.constraintEqualToAnchor( inputContainer.centerXAnchor ).active = true

    tagsTextField.widthAnchor.constraintEqualToAnchor( inputContainer.widthAnchor ).active = true
    tagsTextField.heightAnchor.constraintEqualToAnchor( inputContainer.heightAnchor, multiplier: 0.2 ).active = true

}

func setupButtons()
{
    mainContainer.addSubview( cancelButton )
    mainContainer.addSubview( publicarButton )


    cancelButton.bottomAnchor.constraintEqualToAnchor( mainContainer.bottomAnchor).active = true
    cancelButton.leftAnchor.constraintEqualToAnchor( mainContainer.leftAnchor ).active = true

    cancelButton.widthAnchor.constraintEqualToAnchor( mainContainer.widthAnchor, multiplier:  0.5 ).active = true
    cancelButton.heightAnchor.constraintEqualToAnchor( mainContainer.heightAnchor, multiplier:  0.1).active = true



    publicarButton.bottomAnchor.constraintEqualToAnchor( mainContainer.bottomAnchor).active = true
    publicarButton.leftAnchor.constraintEqualToAnchor( cancelButton.rightAnchor ).active = true

    publicarButton.widthAnchor.constraintEqualToAnchor( mainContainer.widthAnchor, multiplier:  0.5 ).active = true
    publicarButton.heightAnchor.constraintEqualToAnchor( mainContainer.heightAnchor, multiplier:  0.1).active = true
} }

因此，当键盘出现时，滚动视图的底部锚常量会发生变化，因此键盘“顶部锚”是新的底部锚。

Answer 1

由于您描述的约束，布局引擎无法确定滚动视图的内容高度。您应该将底部文本字段固定到滚动视图的底部。这样，滚动视图的内容大小将调整为所有文本字段的最大值。下面是一些你可以放在操场上查看的代码：

import UIKit
import XCPlayground

let scrollView = UIScrollView(frame: CGRect(x: 0, y: 0, width: 200, height: 150))
scrollView.backgroundColor = UIColor.whiteColor()

let textField = UITextField()
textField.translatesAutoresizingMaskIntoConstraints = false
textField.backgroundColor = UIColor.purpleColor()

let otherTextField = UITextField()
otherTextField.translatesAutoresizingMaskIntoConstraints = false
otherTextField.backgroundColor = UIColor.purpleColor()

let otherOtherTextField = UITextField()
otherOtherTextField.translatesAutoresizingMaskIntoConstraints = false
otherOtherTextField.backgroundColor = UIColor.purpleColor()

scrollView.addSubview(textField)

textField.topAnchor.constraintEqualToAnchor(scrollView.topAnchor).active = true
textField.leadingAnchor.constraintEqualToAnchor(scrollView.leadingAnchor).active = true
textField.widthAnchor.constraintEqualToAnchor(scrollView.widthAnchor).active = true

scrollView.addSubview(otherTextField)

otherTextField.topAnchor.constraintEqualToAnchor(textField.bottomAnchor, constant: 60).active = true
otherTextField.leadingAnchor.constraintEqualToAnchor(scrollView.leadingAnchor).active = true
otherTextField.widthAnchor.constraintEqualToAnchor(scrollView.widthAnchor).active = true

scrollView.addSubview(otherOtherTextField)
otherOtherTextField.topAnchor.constraintEqualToAnchor(otherTextField.bottomAnchor, constant: 60).active = true
otherOtherTextField.leadingAnchor.constraintEqualToAnchor(scrollView.leadingAnchor).active = true
otherOtherTextField.widthAnchor.constraintEqualToAnchor(scrollView.widthAnchor).active = true
otherOtherTextField.bottomAnchor.constraintEqualToAnchor(scrollView.bottomAnchor).active = true

scrollView.setNeedsLayout()

XCPlaygroundPage.currentPage.liveView = scrollView

这会将三个文本字段放置在滚动视图中，中心与顶部和底部之间有 60 个点。如果你注释掉：

otherOtherTextField.bottomAnchor.constraintEqualToAnchor(scrollView.bottomAnchor).active = true

助手编辑器中的滚动视图不会滚动，但会滚动。