UIView 子视图没有出现

Posted 2023-02-27

【中文标题】UIView 子视图没有出现

【英文标题】：UIView subviews not appearing

【发布时间】：2017-08-08 17:48:09

【问题描述】：

我有一个带有UIView 的视图控制器。在 UIView 里面我添加了像文本标签这样的元素。当我运行我的代码时，它不存在。

import UIKit

 class EventDetailViewController: UIViewController 

//variables that will hold data sent in through previous event controller
var eventImage = ""
var eventName = ""
var eventDescription = ""
var eventStreet = ""
var eventCity = ""
var eventState = ""
var eventZip = 0
var eventDate = ""
//
lazy var currentEventImage : UIImageView = 
    let currentEvent = UIImageView()
    let imageURL = URL(string: self.eventImage)
    currentEvent.af_setImage(withURL: imageURL!)
    currentEvent.clipsToBounds = true
    currentEvent.translatesAutoresizingMaskIntoConstraints = false
    currentEvent.contentMode = .scaleToFill
    currentEvent.layer.masksToBounds = true
    return currentEvent
()
//will be responsible for creating the UIView that contains relevant event information
let eventInfoContainerView: UIView = 
   let infoContainer = UIView()
    infoContainer.backgroundColor = UIColor.white
    infoContainer.layer.masksToBounds = true
    return infoContainer
()

lazy var eventNameLabel: UILabel = 
    let currentEventName = UILabel()
    currentEventName.text = self.eventName
    currentEventName.translatesAutoresizingMaskIntoConstraints = false
    return currentEventName
()


override func viewDidLoad() 
    super.viewDidLoad()
 view.backgroundColor = UIColor.white
    navigationItem.title = eventName
    self.navigationItem.hidesBackButton = true
    let backButton = UIBarButtonItem(image: UIImage(named: "icons8-Back-64"), style: .plain, target: self, action: #selector(GoBack))
    self.navigationItem.leftBarButtonItem = backButton

    //Subviews will be added here
    view.addSubview(currentEventImage)
    view.addSubview(eventInfoContainerView)
    eventInfoContainerView.addSubview(eventNameLabel)
    //Constraints will be added here
    _ = currentEventImage.anchor(view.centerYAnchor, left: nil, bottom: nil, right: nil, topConstant: -305, leftConstant: 0, bottomConstant: 0, rightConstant: 0, widthConstant: self.view.frame.width, heightConstant: 200)
    _ = eventInfoContainerView.anchor(currentEventImage.bottomAnchor, left: view.leftAnchor, bottom: view.bottomAnchor, right: view.rightAnchor, topConstant: 0, leftConstant: 0, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 0)
     _ = eventNameLabel.anchor(eventInfoContainerView.bottomAnchor, left: view.leftAnchor, bottom: nil, right: nil, topConstant: 20, leftConstant: 32, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 0)





func GoBack()
 _ = self.navigationController?.popViewController(animated: true)


override func didReceiveMemoryWarning() 
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.


 

我有点迷茫，我查看了一个教程，其中他们以类似的方式将元素添加到 UIView，然后事情就出现了。任何见解都会有所帮助。尝试更改多项内容，但没有真正让它出现。我研究了几个答案

这是我设置约束的自定义方法

 import UIKit


extension UIView 

func anchorToTop(_ top: NSLayoutYAxisAnchor? = nil, left: NSLayoutXAxisAnchor? = nil, bottom: NSLayoutYAxisAnchor? = nil, right: NSLayoutXAxisAnchor? = nil) 

    anchorWithConstantsToTop(top, left: left, bottom: bottom, right: right, topConstant: 0, leftConstant: 0, bottomConstant: 0, rightConstant: 0)


func anchorWithConstantsToTop(_ top: NSLayoutYAxisAnchor? = nil, left: NSLayoutXAxisAnchor? = nil, bottom: NSLayoutYAxisAnchor? = nil, right: NSLayoutXAxisAnchor? = nil, topConstant: CGFloat = 0, leftConstant: CGFloat = 0, bottomConstant: CGFloat = 0, rightConstant: CGFloat = 0) 

    translatesAutoresizingMaskIntoConstraints = false

    if let top = top 
        topAnchor.constraint(equalTo: top, constant: topConstant).isActive = true
    

    if let bottom = bottom 
        bottomAnchor.constraint(equalTo: bottom, constant: -bottomConstant).isActive = true
    

    if let left = left 
        leftAnchor.constraint(equalTo: left, constant: leftConstant).isActive = true
    

    if let right = right 
        rightAnchor.constraint(equalTo: right, constant: -rightConstant).isActive = true
    




func anchor(_ top: NSLayoutYAxisAnchor? = nil, left: NSLayoutXAxisAnchor? = nil, bottom: NSLayoutYAxisAnchor? = nil, right: NSLayoutXAxisAnchor? = nil, topConstant: CGFloat = 0, leftConstant: CGFloat = 0, bottomConstant: CGFloat = 0, rightConstant: CGFloat = 0, widthConstant: CGFloat = 0, heightConstant: CGFloat = 0) -> [NSLayoutConstraint] 
    translatesAutoresizingMaskIntoConstraints = false

    var anchors = [NSLayoutConstraint]()

    if let top = top 
        anchors.append(topAnchor.constraint(equalTo: top, constant: topConstant))
    

    if let left = left 
        anchors.append(leftAnchor.constraint(equalTo: left, constant: leftConstant))
    

    if let bottom = bottom 
        anchors.append(bottomAnchor.constraint(equalTo: bottom, constant: -bottomConstant))
    

    if let right = right 
        anchors.append(rightAnchor.constraint(equalTo: right, constant: -rightConstant))
    

    if widthConstant > 0 
        anchors.append(widthAnchor.constraint(equalToConstant: widthConstant))
    

    if heightConstant > 0 
        anchors.append(heightAnchor.constraint(equalToConstant: heightConstant))
    

    anchors.forEach($0.isActive = true)

    return anchors

【问题讨论】：

我没有答案，但是我发现 Xcode 的 View Debugging 功能对这类事情很方便。当屏幕显示您不期望的内容时拍摄屏幕快照。然后可以查看层次结构、约束、离屏视图等线索。

我做了 UIView 存在但标签不存在。当我检查 textlabel 中的变量时，它存储在那里。但没有出现

@SJackson5 - 你需要展示你的.anchor(...) 函数。如果我们不知道该函数在做什么，我们就看不到会发生什么。

您没有正确设置约束，您确定这是在编译，因为 UIView 没有名为 anchor 的方法吗？

@Abizern 那是我自己的自定义方法

【参考方案1】：

好的 - 现在我们看到了您的 .anchor(...) 函数...

标签的 TOP 设置为 eventInfoContainerView 的 BOTTOM 和 topConstant: 20 ... +20

将该值更改为-20（假设您希望标签位于视图底部）：

    _ = eventNameLabel.anchor(eventInfoContainerView.bottomAnchor, left: view.leftAnchor, bottom: nil, right: nil, topConstant: -20, leftConstant: 32, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 0)

假设您的.anchor(...) 功能/扩展工作正常，我认为唯一的错误是您忘记设置：

infoContainer.translatesAutoresizingMaskIntoConstraints = false

当你初始化你的eventInfoContainerView时

【讨论】：

我的自定义方法已经在我的锚函数中处理了这个问题。查看修改

还是没有

由于限制而损失了一个小时。我真诚地感谢帮助人

但是，我必须将其设置为 -400 以将其放置在正确的位置，是否有任何关于为什么错误的提示？

我认为它根本没有被添加到 uiview 中