iOS |以编程方式添加两个视图时出现布局约束错误

Question

我有一段代码可以并排显示图像视图和 UILabel。它根据提供的约束按预期显示，但控制台中有很多警告

这是错误

[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. 
(
    "<NSLayoutConstraint:0x6000003d0190 V:|-(0)-[UIImageView:0x7faa7401b940]   (active, names: '|':Movies_TODO.MovieViewCell:0x7faa7402caa0'custom' )>",
    "<NSLayoutConstraint:0x6000003d05a0 UIImageView:0x7faa7401b940.bottom == Movies_TODO.MovieViewCell:0x7faa7402caa0'custom'.bottom   (active)>",
    "<NSLayoutConstraint:0x6000003d0640 UIImageView:0x7faa7401b940.height == 100   (active)>",
    "<NSLayoutConstraint:0x6000003e7070 'UIView-Encapsulated-Layout-Height' Movies_TODO.MovieViewCell:0x7faa7402caa0'custom'.height == 100.5   (active)>"
)

将尝试通过打破约束来恢复

这是我的一段代码

self.addSubview(movieImageView)
self.addSubview(titleLabel)

movieImageView.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
movieImageView.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true
movieImageView.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
movieImageView.widthAnchor.constraint(equalToConstant: 100).isActive = true

movieImageView.heightAnchor.constraint(equalToConstant: 100).isActive = true

titleLabel.leadingAnchor.constraint(equalTo: movieImageView.trailingAnchor, constant: 20).isActive = true
titleLabel.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
titleLabel.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
titleLabel.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true

Answer 1

您的movieImageView 具有类似height equal to 100 和height equal to super view's height 的约束（这是因为您添加了顶部和底部锚约束）。

---

1 - 如果你想从上到下设置movieImageView，只需删除movieImageView.heightAnchor.constraint(equalToConstant: 100).isActive = true。

---

2 - 如果您想将movieImageView 的高度始终设置为 100，只需删除您不想为 movieImageView 设置的行 ->

// if you want to stick your imageView to bottom delete this
movieImageView.topAnchor.constraint(equalTo: self.topAnchor).isActive = true

// if you want to stick your imageView to top delete this
movieImageView.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true

---

与UIStackView

• 如果您想创建一个TableViewCell 具有左侧图像和右侧标签，您可以使用StackView，您可以不受任何限制地为所欲为。

创建UIStackView

let stackView = UIStackView()

添加您的movieImageView 和titleLabel

stackView.addArrangedSubviews(movieImageView, titleLabel)
stackView.axis = .horizontal
stackView.spacing = 20.0

将您的stackView 添加到super.view

self.addSubview(stackView)
stackView.translatesAutoresizingMaskIntoConstraints = false

stackView.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
stackView.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true

stackView. trailingAnchor.constraint(equalTo: self. trailingAnchor).isActive = true
stackView.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true

如果你想设置movieImageView的图片宽度，你应该设置movieImageView的Content Hugging Priority

movieImageView.setContentHuggingPriority(.defaultHigh, for: .horizontal)

如果你想设置titleLabel的宽度从它的文本并且比imageView更耐，你应该设置titleLabel的Compression Resistance Priority

titleLabel.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)

---

奖金

Intrinsic Content Size

UIStackView Guide

UIStackView Example of Hackingwithswift

Answer 2

你已经设置了你的movieImageView的底部锚点和顶部锚点，它们间接表示你的movieImageView的高度。

设置高度后，您再次将高度更改为某个恒定值 100。

为避免此警告删除

movieImageView.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true

此警告是由于对同一属性的冗余约束。

你试试下面的约束

    movieImageView.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor).isActive = true
    movieImageView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
    movieImageView.widthAnchor.constraint(equalToConstant: 100).isActive = true
    movieImageView.heightAnchor.constraint(equalToConstant: 100).isActive = true

    titleLabel.leadingAnchor.constraint(equalTo: movieImageView.trailingAnchor, constant: 20).isActive = true
    titleLabel.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor).isActive = true
    titleLabel.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
    titleLabel.bottomAnchor.constraint(equalTo: self.movieImageView.bottomAnchor).isActive = true

这个约束的结果是