快速如何以编程方式设置自动布局

Question

我在一个视图中有按钮，我想要像这样在 potrait 模式下 -

通过以下代码实现-

//original potrait mode/////

 import UIKit
 class PotraitViewController: UIViewController {
 override func viewDidLoad() {
 let buttonred = UIButton()
 buttonred.backgroundColor = UIColor.red
 let buttonblue = UIButton()
 buttonblue.backgroundColor = UIColor.blue
 let landscapesmallview = UIView()
 view.addSubview(landscapesmallview)
 landscapesmallview.addSubview(buttonred)
 landscapesmallview.addSubview(buttonblue)
 buttonred.translatesAutoresizingMaskIntoConstraints = false
 buttonblue.translatesAutoresizingMaskIntoConstraints = false
 NSLayoutConstraint.activate([

    buttonred.topAnchor.constraint(equalTo: view.topAnchor,constant: 200),
    buttonred.centerXAnchor.constraint(equalTo: view.centerXAnchor),
    buttonred.trailingAnchor.constraint(equalTo: view.trailingAnchor,constant:-20),
    buttonred.widthAnchor.constraint(equalToConstant: 50),
    //-------
    buttonblue.topAnchor.constraint(equalTo: buttonred.bottomAnchor,constant: 40),
    buttonblue.leadingAnchor.constraint(equalTo: buttonred.leadingAnchor),
    buttonblue.trailingAnchor.constraint(equalTo:buttonred.trailingAnchor),
    buttonblue.widthAnchor.constraint(equalTo: buttonred.widthAnchor)

      ])
    }
  }

在横向模式下我想要这样 -

通过以下代码实现-

 // original lanscape mode/////

import UIKit
class LandscapeViewController: UIViewController {
override func viewDidLoad() {
let buttonred = UIButton()
buttonred.backgroundColor = UIColor.red
let buttonblue = UIButton()
buttonblue.backgroundColor = UIColor.blue
view.addSubview(buttonred)
view.addSubview(buttonblue)
buttonred.translatesAutoresizingMaskIntoConstraints = false
buttonblue.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([

    buttonred.centerYAnchor.constraint(equalTo: view.centerYAnchor),
    buttonred.leadingAnchor.constraint(equalTo: view.leadingAnchor,constant:40),
    buttonred.trailingAnchor.constraint(equalTo: view.centerXAnchor,constant:-20),
    buttonred.widthAnchor.constraint(equalToConstant: 50),

    //-------
    buttonblue.centerYAnchor.constraint(equalTo: buttonred.centerYAnchor),
    buttonblue.leadingAnchor.constraint(equalTo: view.centerXAnchor,constant:40),
    buttonblue.trailingAnchor.constraint(equalTo: view.trailingAnchor,constant:-20),
    buttonblue.widthAnchor.constraint(equalTo:buttonred.widthAnchor)

       ])
     }
  }

因此，我尝试使用以下代码通过屏幕旋转来实现，即借助以下代码以编程方式在纵向和横向视图中实现两种不同的布局：-

import UIKit

class NewViewController: UIViewController {
override func viewDidLoad() {
let buttonredlandscape = UIButton()
buttonredlandscape.backgroundColor = UIColor.red
let buttonbluelandscape = UIButton()
buttonbluelandscape.backgroundColor = UIColor.blue
let buttonredportrait = UIButton()
buttonredportrait.backgroundColor = UIColor.red
let buttonblueportrait = UIButton()
buttonblueportrait.backgroundColor = UIColor.blue

let landscapesmallview = UIView()
let portraitsmallview = UIView()
landscapesmallview.backgroundColor = UIColor.gray
portraitsmallview.backgroundColor = UIColor.purple
landscapesmallview.frame = view.frame
portraitsmallview.frame = view.frame
view.addSubview(landscapesmallview)
view.addSubview(portraitsmallview)


landscapesmallview.addSubview(buttonredlandscape)
landscapesmallview.addSubview(buttonbluelandscape)
portraitsmallview.addSubview(buttonredportrait)
portraitsmallview.addSubview(buttonblueportrait)
buttonredlandscape.translatesAutoresizingMaskIntoConstraints = false
buttonbluelandscape.translatesAutoresizingMaskIntoConstraints = false
buttonredportrait.translatesAutoresizingMaskIntoConstraints = false
buttonblueportrait.translatesAutoresizingMaskIntoConstraints = false

NSLayoutConstraint.activate([

     buttonredlandscape.centerYAnchor.constraint(equalTo:landscapesmallview.centerYAnchor),
      buttonredlandscape.topAnchor.constraint(equalTo:landscapesmallview.topAnchor,constant:40),
    buttonredlandscape.trailingAnchor.constraint(equalTo:   landscapesmallview.centerXAnchor,constant:-20),
    buttonredlandscape.heightAnchor.constraint(equalTo:   landscapesmallview.heightAnchor,constant:50),

    buttonbluelandscape.centerYAnchor.constraint(equalTo:buttonredlandscape.centerYAnchor),
    buttonbluelandscape.leadingAnchor.constraint(equalTo: landscapesmallview.centerXAnchor,constant:40),
    buttonbluelandscape.trailingAnchor.constraint(equalTo: landscapesmallview.trailingAnchor,constant:-20),
    buttonbluelandscape.heightAnchor.constraint(equalTo: buttonredlandscape.heightAnchor),


    buttonredportrait.topAnchor.constraint(equalTo: portraitsmallview.topAnchor,constant: 200),
    buttonredportrait.centerXAnchor.constraint(equalTo: portraitsmallview.centerXAnchor),
    buttonredportrait.trailingAnchor.constraint(equalTo: portraitsmallview.trailingAnchor,constant:-20),
    buttonredportrait.widthAnchor.constraint(equalTo: buttonredportrait.widthAnchor),

    buttonblueportrait.topAnchor.constraint(equalTo: buttonredportrait.bottomAnchor,constant: 40),
    buttonblueportrait.leadingAnchor.constraint(equalTo: buttonredportrait.leadingAnchor),
    buttonblueportrait.trailingAnchor.constraint(equalTo:buttonredportrait.trailingAnchor),
    buttonblueportrait.widthAnchor.constraint(equalTo: buttonredportrait.widthAnchor)


     ])

//-------



func viewWillTransition(to size: CGSize, with coordinator:    ) {
    if UIDevice.current.orientation.isLandscape {
        landscapesmallview.translatesAutoresizingMaskIntoConstraints = false
        portraitsmallview.translatesAutoresizingMaskIntoConstraints = true
     } else if UIDevice.current.orientation.isPortrait {
        portraitsmallview.translatesAutoresizingMaskIntoConstraints = false
        landscapesmallview.translatesAutoresizingMaskIntoConstraints = true

        }
      }
    }
 }

在肖像模式下显示 -

在横向模式下显示 -

如何以编程方式实现我想要的，即每次用户旋转设备时，最上面的 2 个按钮以编程方式重新排列自己。它不仅仅是按钮。它可以是标签、图像、collectionview 等或任何东西。结果是我想以编程方式在横向和纵向模式下实现两种不同的布局，而与设备无关。

注意点：-

i) 我曾尝试将 NSLayoutAnchor 与“NSLayoutConstraint.activate”一起使用，因为苹果推荐使用它，但如果可以使用视觉格式等其他方法使代码更短（更快），我也可以/

ii) 如果可能的话，我不想使用stackview或containerview，因为标签、按钮等可以有更多类型，但如果没有其他方法，我会使用它。

iii) 我的代码符合 DRY 原则吗？

另外，伙计们，拜托，我不应该得到负分，因为据我所知，以前没有人问过这个问题。请大家不要给差评，鼓励我。

Answer 1

有多种方法可以做到这一点。一种方法：

• 声明两个“约束”数组
  • 一个持有“狭义”约束的人
  • 一个持有“宽视野”约束的人
• 根据需要激活/停用约束

这是一个完整的例子：

class ChangeLayoutViewController: UIViewController {

    let redButton: UIButton = {
        let v = UIButton()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .red
        v.setTitle("Red Button", for: [])
        return v
    }()

    let blueButton: UIButton = {
        let v = UIButton()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .blue
        v.setTitle("Blue Button", for: [])
        return v
    }()

    var narrowConstraints: [NSLayoutConstraint] = [NSLayoutConstraint]()
    var wideConstraints: [NSLayoutConstraint] = [NSLayoutConstraint]()

    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(redButton)
        view.addSubview(blueButton)

        let g = view.safeAreaLayoutGuide

        var c: NSLayoutConstraint

        // MARK: - narrow orientation

        // constrain redButton above blueButton

        // constrain redButton leading and trailing to safe-area (with 8-pts on each side)
        c = redButton.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 8.0)
        narrowConstraints.append(c)
        c = redButton.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -8.0)
        narrowConstraints.append(c)

        // constrain blueButton leading and trailing to safe-area (with 8-pts on each side)
        c = blueButton.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 8.0)
        narrowConstraints.append(c)
        c = blueButton.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -8.0)
        narrowConstraints.append(c)

        // constrain redButton top 40-pts from safe-area top
        c = redButton.topAnchor.constraint(equalTo: g.topAnchor, constant: 40.0)
        narrowConstraints.append(c)
        // constrain blueButton top 20-pts from redButton bottom
        c = blueButton.topAnchor.constraint(equalTo: redButton.bottomAnchor, constant: 20.0)
        narrowConstraints.append(c)


        // MARK: - wide orientation

        // constrain redButton & blueButton side-by-side
        //  with equal widths and 8-pts between them

        // constrain redButton leading 8-pts from safe-area leading
        c = redButton.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 8.0)
        wideConstraints.append(c)
        // constrain blueButton trailing 8-pts from safe-area trailing
        c = blueButton.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -8.0)
        wideConstraints.append(c)

        // constrain blueButton leading 8-pts from redButton trailing
        c = blueButton.leadingAnchor.constraint(equalTo: redButton.trailingAnchor, constant: 8.0)
        wideConstraints.append(c)

        // constrain buttons to equal widths
        c = blueButton.widthAnchor.constraint(equalTo: redButton.widthAnchor)
        wideConstraints.append(c)

        // constrain both buttons centerY to safe-area centerY
        c = redButton.centerYAnchor.constraint(equalTo: g.centerYAnchor)
        wideConstraints.append(c)
        c = blueButton.centerYAnchor.constraint(equalTo: g.centerYAnchor)
        wideConstraints.append(c)

        // activate initial constraints based on view width:height ratio
        changeConstraints(view.frame.width > view.frame.height)

    }

    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransition(to: size, with: coordinator)
        // change active set of constraints based on view width:height ratio
        self.changeConstraints(size.width > size.height)
    }

    func changeConstraints(_ useWide: Bool) -> Void {
        if useWide {
            NSLayoutConstraint.deactivate(narrowConstraints)
            NSLayoutConstraint.activate(wideConstraints)
        } else {
            NSLayoutConstraint.deactivate(wideConstraints)
            NSLayoutConstraint.activate(narrowConstraints)
        }
    }

}

结果：

Answer 2

refer this this image for handling in device orientation

在堆栈视图中获取两个按钮并使堆栈视图垂直居中并水平居中