我正在努力学习在没有故事板的情况下构建视图。我试图构建一个滚动视图。滚动视图上有一个UISearchBar，一个带有图像和UILabel的UIImageView。它有效，但没有任何内容移动。内容都冻结在原地，就像无论我滚动多远，搜索栏都会一直在页面顶部一样。以及底部的图像。我附上了一段视频来说明我的意思。还有一个问题，因为没有一个内容是我想要的，但这是另一个问题。我意识到这可能是因为我对没有故事板的约束、自动布局和构建视图了解不够。
这是视频
class HomePageViewController: UIViewController {
var searchedText: String = ""
let label = UILabel()
let searchBar: UISearchBar = {
let searchBar = UISearchBar()
searchBar.placeholder = "Where are you going?"
searchBar.translatesAutoresizingMaskIntoConstraints = false
searchBar.barTintColor = .systemCyan
searchBar.searchTextField.backgroundColor = .white
searchBar.layer.cornerRadius = 5
return searchBar
}()
let homeImage: UIImageView = {
let homeImage = UIImageView()
homeImage.translatesAutoresizingMaskIntoConstraints = false
homeImage.clipsToBounds = true
return homeImage
}()
let scrollView: UIScrollView = {
let scrollView = UIScrollView()
scrollView.translatesAutoresizingMaskIntoConstraints = false
scrollView.backgroundColor = .systemMint
scrollView.contentSize = CGSize(width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height * 30)
return scrollView
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .systemPink
// setupLayout()
// tried this here doesn't do anything for me
}
func setupLayout() {
view.addSubview(scrollView)
self.scrollView.addSubview(searchBar)
homeImage.image = UIImage(named: "Treehouse")
self.scrollView.addSubview(homeImage)
label.text = "Inspiration for your next trip..."
self.scrollView.addSubview(label)
// not sure where this label is being added I want it to be underneath the image but it isn't t
let safeG = view.safeAreaLayoutGuide
let viewFrame = view.bounds
NSLayoutConstraint.activate([
scrollView.topAnchor.constraint(equalTo: view.topAnchor, constant: -10),
scrollView.leftAnchor.constraint(equalTo: view.leftAnchor),
scrollView.rightAnchor.constraint(equalTo: view.rightAnchor),
scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
searchBar.topAnchor.constraint(equalTo: safeG.topAnchor, constant: 50.0),
searchBar.widthAnchor.constraint(equalTo: safeG.widthAnchor, multiplier: 0.9),
searchBar.centerXAnchor.constraint(equalTo: safeG.centerXAnchor),
homeImage.topAnchor.constraint(equalTo: safeG.topAnchor, constant: 150),
homeImage.widthAnchor.constraint(equalTo: safeG.widthAnchor, multiplier: 1.1),
homeImage.centerXAnchor.constraint(equalTo: safeG.centerXAnchor),
homeImage.heightAnchor.constraint(equalToConstant: viewFrame.height/2),
label.topAnchor.constraint(equalTo: homeImage.bottomAnchor, constant: 100)
])
// was doing all this in viewDidLayoutSubviews but not sure if this is better place for it
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
setupLayout()
// tried this in viewDidLoad() and it didn't solve it.
}
}
如有任何帮助，将不胜感激
首先，当约束UIScrollView中的子视图时，应该将它们约束到滚动视图的Content Layout Guide。您将它们限制在视图的安全区域布局指南中，这样它们就永远不会去任何地方。
其次，很难在滚动视图中将子视图居中，因为滚动视图可以水平和垂直滚动。所以它实际上并没有一个"；中心">
您可以将子视图放在堆栈视图中，或者，非常常见的是，使用UIView作为"；内容"；视图以容纳子视图。如果将内容视图的"宽度"约束为滚动视图的Frame Layout Guide宽度，则可以将子视图水平居中。
第三，评论你的约束非常有帮助，这样你就可以确切地知道你期望他们做什么。
以下是您发布代码的修改版本：
class HomePageViewController: UIViewController {
var searchedText: String = ""
let label: UILabel = {
let v = UILabel()
v.translatesAutoresizingMaskIntoConstraints = false
return v
}()
let searchBar: UISearchBar = {
let searchBar = UISearchBar()
searchBar.placeholder = "Where are you going?"
searchBar.translatesAutoresizingMaskIntoConstraints = false
searchBar.barTintColor = .systemCyan
searchBar.searchTextField.backgroundColor = .white
searchBar.layer.cornerRadius = 5
return searchBar
}()
let homeImage: UIImageView = {
let homeImage = UIImageView()
homeImage.translatesAutoresizingMaskIntoConstraints = false
homeImage.clipsToBounds = true
return homeImage
}()
let scrollView: UIScrollView = {
let scrollView = UIScrollView()
scrollView.translatesAutoresizingMaskIntoConstraints = false
scrollView.backgroundColor = .systemMint
// don't do this
//scrollView.contentSize = CGSize(width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height * 30)
return scrollView
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .systemPink
setupLayout()
}
func setupLayout() {
view.addSubview(scrollView)
//homeImage.image = UIImage(named: "Treehouse")
homeImage.image = UIImage(named: "natureBKG")
label.text = "Inspiration for your next trip..."
// let's use a UIView to hold the "scroll content"
let contentView = UIView()
contentView.translatesAutoresizingMaskIntoConstraints = false
// give it a green background so we can see it
contentView.backgroundColor = .green
contentView.addSubview(searchBar)
contentView.addSubview(homeImage)
contentView.addSubview(label)
scrollView.addSubview(contentView)
let safeG = view.safeAreaLayoutGuide
let svContentG = scrollView.contentLayoutGuide
let svFrameG = scrollView.frameLayoutGuide
NSLayoutConstraint.activate([
// constrain scrollView to all 4 sides of view
// (generally, constrain to safe-area, but this is what you had)
scrollView.topAnchor.constraint(equalTo: view.topAnchor),
scrollView.leftAnchor.constraint(equalTo: view.leftAnchor),
scrollView.rightAnchor.constraint(equalTo: view.rightAnchor),
scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
// constrain contentView to all 4 sides of scroll view's Content Layout Guide
contentView.topAnchor.constraint(equalTo: svContentG.topAnchor, constant: 0.0),
contentView.leadingAnchor.constraint(equalTo: svContentG.leadingAnchor, constant: 0.0),
contentView.trailingAnchor.constraint(equalTo: svContentG.trailingAnchor, constant: 0.0),
contentView.bottomAnchor.constraint(equalTo: svContentG.bottomAnchor, constant: 0.0),
// constrain contentView Width equal to scroll view's Frame Layout Guide Width
contentView.widthAnchor.constraint(equalTo: svFrameG.widthAnchor),
// constrain searchBar Top to contentView Top + 50
searchBar.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 50.0),
// constrain searchBar Width to 90% of contentView Width
searchBar.widthAnchor.constraint(equalTo: contentView.widthAnchor, multiplier: 0.9),
// constrain searchBar centerX to contentView centerX
searchBar.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
// constrain homeImage Top to searchBar Bottom + 40
homeImage.topAnchor.constraint(equalTo: searchBar.bottomAnchor, constant: 40.0),
// constrain homeImage Width equal to contentView Width
homeImage.widthAnchor.constraint(equalTo: contentView.widthAnchor, multiplier: 1.0),
// constrain homeImage centerX to contentView centerX
homeImage.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
// constrain homeImage Height to 1/2 of scroll view frame Height
homeImage.heightAnchor.constraint(equalTo: svFrameG.heightAnchor, multiplier: 0.5),
// you probably won't get vertical scrolling yet, so increase the vertical space
// between the homeImage and the label by changing the constant
// from 100 to maybe 400
// constrain label Top to homeImage Bottom + 100
label.topAnchor.constraint(equalTo: homeImage.bottomAnchor, constant: 100.0),
// constrain label centerX to contentView centerX
label.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
// constrain label Bottom to contentView Bottom - 20
label.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -20.0),
])
}
}