尝试添加UIImageView数组的约束

问题描述

我创建了UIImageViews的数组，并在其中存储了5个图像视图，没有任何约束。

lazy var albumImage: UIImageView = {
    let image = UIImage(named: "authorizationImage")
    let imageView = UIImageView(image: image)
    imageView.frame = CGRect(x: 0,y: 0,width: 50,height: 50)
    imageView.layer.cornerRadius = 10
    imageView.backgroundColor = .black
    imageView.layer.masksToBounds = true
    imageView.translatesAutoresizingMaskIntoConstraints = false
    return imageView
}()

lazy var albumImages: [UIImageView] = [albumImage,albumImage,albumImage]

我将它们添加到了UIView中：

for row in 0...(albumImages.count-1){
    backView.addSubview(albumImages[row])
}

并尝试基于UILabel设置每个约束，我在UIView上拥有约束：

for row in 0...(albumImages.count-1){
    let distanceFromTop = ((row*30) + (row+1)*10)
    print("geez \(row) distance \(distanceFromTop)")
    albumImages[row].topAnchor.constraint(equalTo: registrationTime.bottomAnchor,constant: CGFloat(distanceFromTop)).isActive = true
    albumImages[row].leftAnchor.constraint(equalTo: backView.leftAnchor,constant: 20).isActive = true
    albumImages[row].rightAnchor.constraint(equalTo: albumImages[row].leftAnchor,constant: 30).isActive = true
    albumImages[row].heightAnchor.constraint(equalToConstant: 30).isActive = true
}

我可以在模拟器上看到第一个UIImageView。但是，未显示其他4个。我在控制台中收到错误消息：

geez 0 distance 10
geez 1 distance 50
2020-08-12 17:16:38.174252+0900 WhosFan[24100:2336027] [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:0x60000167cbe0 V:[UILabel:0x7f97ae8603b0'Based on (KST) : 2020.08....']-(10)-[UIImageView:0x7f97aeb20d60]   (active)>","<NSLayoutConstraint:0x6000016777f0 V:[UILabel:0x7f97ae8603b0'Based on (KST) : 2020.08....']-(50)-[UIImageView:0x7f97aeb20d60]   (active)>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x6000016777f0 V:[UILabel:0x7f97ae8603b0'Based on (KST) : 2020.08....']-(50)-[UIImageView:0x7f97aeb20d60]   (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful.

我检查了是否以错误的顺序添加了子视图。但是，一切看起来都很好：

 override func setSelected(_ selected: Bool,animated: Bool) {
    super.setSelected(selected,animated: animated)
    addSubview(backView)
    backView.addSubview(cellTitle)
    backView.addSubview(registrationTime)
    addAlbumImages()
    setupConstraints()
    // Configure the view for the selected state
}
private func setupConstraints(){
    setUpCellTitleConstraints()
    setUpRegistrationDateLabelConstraints()
    setupAlbumImagesConstraints()
}

我在这个问题上呆了近2个小时。请任何帮助。 这是我的模拟器的图像：

解决方法

您仅在此处创建一个图像视图（不是5！），并将同一图像视图添加到数组5次：

lazy var albumImages: [UIImageView] = [albumImage,albumImage,albumImage]

这就是为什么所有约束都被破坏，并且只显示一个图像视图的原因。只有一个图像视图，并且该图像视图的最高锚点必须同时距registrationTime.bottomAnchor 10、50、90、130和170点！

无论如何，每次将它们添加到数组时都应创建一个新的图像视图。一种实现方法是使albumImage成为方法createAlbumImageView：

func createAlbumImageView() -> UIImageView {
    let image = UIImage(named: "authorizationImage")
    let imageView = UIImageView(image: image)
    imageView.frame = CGRect(x: 0,y: 0,width: 50,height: 50)
    imageView.layer.cornerRadius = 10
    imageView.backgroundColor = .black
    imageView.layer.masksToBounds = true
    imageView.translatesAutoresizingMaskIntoConstraints = false
    return imageView
}

然后可以像这样声明数组：

lazy var albumImages: [UIImageView] = [
    createAlbumImageView(),createAlbumImageView(),]

---

您的图像视图似乎在垂直线上，且间距多少相等。我不确定不相等的间距是否仅仅是由另一个错误引起的。如果需要相等的间距，则可以改用垂直的UIStackView。