如何在iOS Swift中以中心对齐方式将subView添加到anotherSubView。

Question

我正在使用Lottie库制作动画。我将lottieFile作为subView加载到anotherSubView中，但未在中心对齐。我尝试使用中心属性，如下所示：

@IBOutlet weak var viewOn: UIView!

let animationView = LOTAnimationView(name: "restless_gift_ii") {
animationView.loopAnimation = true
animationView.contentMode = .scaleToFill
animationView.animationSpeed = 1
animationView.backgroundColor = UIColor.black
animationView.frame.size = viewOn.frame.size
animationView.center.x = viewOn.center.x
animationView.center.y = viewOn.center.y
viewOn.addSubview(animationView) }

Answer 1

您可以以编程方式使用自动布局来将动画视图居中对齐到其超级视图中。

在这里，我添加了两种添加animationView中心对齐的方法，还添加了一些注释以便理解。

if let animationView = LOTAnimationView(name: "4_bar_loop") {

        animationView.loopAnimation = true
        animationView.contentMode = .scaleToFill
        animationView.animationSpeed = 1
        animationView.backgroundColor = UIColor.black

        self.viewOn.addSubview(animationView)

        animationView.translatesAutoresizingMaskIntoConstraints = false

        // Apply these constrains if you want animation size should be same as super view.
        self.viewOn.addConstraint(NSLayoutConstraint(item: animationView, attribute: .leading, relatedBy: .equal, toItem: self.viewOn, attribute: .leading, multiplier: 1.0, constant: 1))
        self.viewOn.addConstraint(NSLayoutConstraint(item: animationView, attribute: .trailing, relatedBy: .equal, toItem: self.viewOn, attribute: .trailing, multiplier: 1.0, constant: 1))
        self.viewOn.addConstraint(NSLayoutConstraint(item: animationView, attribute: .top, relatedBy: .equal, toItem: self.viewOn, attribute:.top, multiplier: 1.0, constant: 1))
        self.viewOn.addConstraint(NSLayoutConstraint(item: animationView, attribute: .bottom, relatedBy: .equal, toItem: self.viewOn, attribute: .bottom, multiplier: 1.0, constant: 1))


        // Apply these constraint if you want animationView with fixed height and width and center of super view.
//            self.viewOn.addConstraint(NSLayoutConstraint(item: animationView, attribute: .centerX, relatedBy: .equal, toItem: self.viewOn, attribute: .centerX, multiplier: 1.0, constant: 1))
//            self.viewOn.addConstraint(NSLayoutConstraint(item: animationView, attribute: .centerY, relatedBy: .equal, toItem: self.viewOn, attribute: .centerY, multiplier: 1.0, constant: 1))
//            animationView.addConstraint(NSLayoutConstraint(item: animationView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 100))
//            animationView.addConstraint(NSLayoutConstraint(item: animationView, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 100))
        }

Answer 2

你可以像下面的代码一样以编程方式完成我希望这对你有帮助

import UIKit

class ViewController: UIViewController {

    let firstView:UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        view.backgroundColor = UIColor.blue
        return view
    }()

    let secondView:UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        view.backgroundColor = UIColor.orange
        return view
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        setupViews()
    }

    func setupViews(){

        view.addSubview(firstView)
        firstView.centerYAnchor.constraint(equalTo: self.view.centerYAnchor, constant: 0).isActive = true
        firstView.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: 0).isActive = true
        firstView.widthAnchor.constraint(equalToConstant: 100).isActive = true
        firstView.heightAnchor.constraint(equalToConstant: 100).isActive = true

        // second view
        firstView.addSubview(secondView)
        secondView.centerYAnchor.constraint(equalTo: firstView.centerYAnchor, constant: 0).isActive = true
        secondView.centerXAnchor.constraint(equalTo: firstView.centerXAnchor, constant: 0).isActive = true
        secondView.widthAnchor.constraint(equalToConstant: 50).isActive = true
        secondView.heightAnchor.constraint(equalToConstant: 50).isActive = true

    }

}