如何使背景图像正确适合滚动视图？

Posted 2023-03-10

【中文标题】如何使背景图像正确适合滚动视图？

【英文标题】：How to make background image fit properly in scroll view?

【发布时间】：2018-09-11 17:44:43

【问题描述】：

scaleAspectfit 似乎不起作用。我试图让我的整个背景图像稍微适合背景，看到更多的图像。我添加了一个滚动视图，以便用户可以上下滚动一点来查看图像。

但是，我的应用太放大了图像。

lazy var scrollView: UIScrollView = 
    let view = UIScrollView()
    view.translatesAutoresizingMaskIntoConstraints = false
    view.contentSize.height = 800
    view.bounces = true
    return view
() 

覆盖 func viewDidLoad() super.viewDidLoad()

    let backgroundImage = UIImageView(frame: UIScreen.main.bounds)
    backgroundImage.image = UIImage(named: "backgroundImage.png")
    backgroundImage.contentMode = UIViewContentMode.scaleAspectFit
    view.insertSubview(backgroundImage, at: 0)

    view.addSubview(scrollView)
    scrollView.anchor(top: view.topAnchor, left: view.leftAnchor, bottom: view.bottomAnchor, right: view.rightAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)

    scrollView.addSubview(backgroundImage)
    backgroundImage.center(x: scrollView.centerXAnchor, y: scrollView.centerYAnchor)


 

// 如果你们想知道，这只是我用于自动布局的扩展

extension UIView 

func anchor(top: NSLayoutYAxisAnchor?, left: NSLayoutXAxisAnchor?, bottom: NSLayoutYAxisAnchor?, right: NSLayoutXAxisAnchor?, paddingTop: CGFloat, paddingLeft: CGFloat, paddingBottom: CGFloat, paddingRight: CGFloat, width: CGFloat, height: CGFloat) 

    translatesAutoresizingMaskIntoConstraints = false

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

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

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

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

    if width != 0 
        widthAnchor.constraint(equalToConstant: width).isActive = true
    

    if height != 0 
        heightAnchor.constraint(equalToConstant: height).isActive = true
    

func center(x: NSLayoutXAxisAnchor?, y: NSLayoutYAxisAnchor? ) 

    translatesAutoresizingMaskIntoConstraints = false

    if let x = x 
        centerXAnchor.constraint(equalTo: x).isActive = true
    

    if let y = y 
        centerYAnchor.constraint(equalTo: y).isActive = true
    

【参考方案1】：

首先您在此处的 2 个地方添加相同的 imageView

view.insertSubview(backgroundImage, at: 0)

这里

scrollView.addSubview(backgroundImage)

所以最终它只会被添加到滚动视图中，因为它是一个对象

其次你需要像这样约束imageView

backgroundImage.anchor(top: scrollView.topAnchor, left: scrollView.leftAnchor, bottom: scrollView.bottomAnchor, right: scrollView.rightAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)

然后imageView会根据scrollView的内容进行拉伸

第三个contentMode应该是

backgroundImage.contentMode =.scaleToFill // or .scaleAspectFill

应该提一下，可以将imageView添加到self.view，并使scrollView背景透明，避免拉伸导致imageView失去质量和方面

【讨论】：

我实际上最终在 swift 之外缩放了我的图片以正确适应应用程序，但您的回答帮助我了解了更多滚动和视图。谢谢