如何使用 swift 以编程方式添加具有一些约束的图像视图？答案

【问题标题】：how to add image view with some constraints programmatically using swift?如何使用 swift 以编程方式添加具有一些约束的图像视图？
【发布时间】：2019-04-30 08:08:20
【问题描述】：

我是 iOS 开发的新手。如果使用故事板，我可以像这样在视图控制器中放置一个图像视图

我需要以编程方式制作类似的东西。

所以我有一个名为 RevealingSplashView 的库中的自定义视图，但我需要向该自定义 UI 视图添加一个图像视图。我只知道添加图像视图，可能是这样的

let imageName = "yourImage.png"
let image = UIImage(named: imageName)
let imageView = UIImageView(image: image!)
imageView.frame = CGRect(x: 0, y: 0, width: 100, height: 200)
revealingSplashView.addSubview(imageView)

但我不知道如何将该约束设置为图像视图

一个。对齐到中心 x 到 superview

b.与 superview 0.8 的比例宽度

c。高度限制 = 25

d。将底部对齐到安全区域 = 32

怎么做？

这是我之前想要添加图像视图的代码

let screenSize = UIScreen.main.bounds
            let iconWidth = (screenSize.width) * 0.8
            let iconHeight = iconWidth * 1 // ratio 1:1
            revealingSplashView = RevealingSplashView(iconImage: UIImage(named: "Loading Page Asset")!,iconInitialSize: CGSize(width: iconWidth, height: iconHeight), backgroundColor: AppColor.mainYellow.getUIColor())
            revealingSplashView.animationType = SplashAnimationType.twitter
            revealingSplashView.imageView?.contentMode = .scaleAspectFill


            // add loading indicator to RevealingSplashView Programatically
            revealingSplashViewIndicator.color = UIColor.white
            revealingSplashViewIndicator.frame = CGRect(x: 0.0, y: 0.0, width: 30.0, height: 30.0)
            revealingSplashViewIndicator.center =  CGPoint(x: self.view.center.x, y: self.view.center.y + (iconHeight/2) + 64 )
            revealingSplashView.addSubview(revealingSplashViewIndicator)
            revealingSplashViewIndicator.bringSubviewToFront(self.revealingSplashView)
            revealingSplashViewIndicator.startAnimating()

            let window = UIApplication.shared.keyWindow
            window?.addSubview(revealingSplashView)

【问题讨论】：

标签： ios swift autolayout

【解决方案1】：

我推荐使用锚点：

let imageName = "yourImage.png"
let image = UIImage(named: imageName)
let imageView = UIImageView(image: image!)
imageView.frame = CGRect(x: 0, y: 0, width: 100, height: 200)
revealingSplashView.addSubview(imageView)

// you need to turn off autoresizing masks (storyboards do this automatically)
imageView.translatesAutoresizingMaskIntoConstraints = false

// setup constraints, it is recommended to activate them through `NSLayoutConstraint.activate`
// instead of `constraint.isActive = true` because of performance reasons
NSLayoutConstraint.activate([
    imageView.centerXAnchor.constraint(equalTo: revealingSplashView.centerXAnchor),
    imageView.widthAnchor.constraint(equalTo: revealingSplashView.widthAnchor, multiplier: 0.8),
    imageView.heightAnchor.constraint(equalToConstant: 25),
    imageView.bottomAnchor.constraint(equalTo: revealingSplashView.safeAreaLayoutGuide.bottomAnchor, constant: -32),
    ])

【讨论】：

不幸的是，它使我的应用程序崩溃：*** 由于未捕获的异常“NSGenericException”而终止应用程序，原因：“无法使用锚激活约束 <0x283c9b7c0><0x283c36e40>

【解决方案2】：

要以编程方式添加约束，您需要设置

imageView.translatesAutoresizingMaskIntoConstraints = false

然后你可以设置约束：

imageView.widthAnchor.constraint(equalTo: revealingSplashView.widthAnchor, multiplier: 0.8).isActive = true
imageView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
imageView.heightAnchor.constraint(equalToConstant: 25).isActive = true
imageView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true

如果你想激活你需要设置的约束

isActive = true

如果你支持 iOS

【讨论】：

不幸的是，它使我的应用程序崩溃，错误消息：*** 由于未捕获的异常“NSGenericException”而终止应用程序，原因：“无法使用锚激活约束 <0x280d18f80 width><0x280d18cc0>

【解决方案3】：

revealingSplashView.addSubview(imageView)

imageView.centerXAnchor.constraint(equalTo: revealingSplashView.centerXAnchor).isActive = true
imageView.widthAnchor.constraint(equalTo: revealingSplashView.widthAnchor, multiplier: 0.8).isActive = true
imageView.heightAnchor.constraint(equalToConstant: 25).isActive = true
imageView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
imageView.translatesAutoresizingMaskIntoConstraints = false

【讨论】：