爲自定義進度條設置動畫寬度約束Autolayout

Question

我正在嘗試創建一個簡單的水平進度欄視圖，並且想要動畫我的寬度約束。

出於測試目的，我創建了一個按鈕，可以在點擊時增加進度條的百分比。

當我點擊按鈕時，寬度約束按預期動畫。但是，如果我在初始化組件時嘗試設置一個百分比，整個視圖就會生成動畫，這不是我想要的。

class ProgressBar: UIView { 
    private let progressView: UIView 
    private var progressBarWidth: NSLayoutConstraint? = nil 

    var percentage: Double = 0 { 
     didSet { 
      updateProgress() 
     } 
    } 

    init() { 
     progressView = UIView() 
     super.init(frame: .zero) 
     setupBackgroundBar() 
     setupProgressView() 
    } 

    required init?(coder aDecoder: NSCoder) { 
     fatalError("init(coder:) has not been implemented") 
    } 

    func setupBackgroundBar() { 
     self.heightAnchor.constraint(equalToConstant: 10).isActive = true 
     self.backgroundColor = UIColor(colorLiteralRed: 1, green: 1, blue: 1, alpha: 0.5) 
    } 

    private func setupProgressView(){ 
     self.addSubview(progressView) 
     progressView.translatesAutoresizingMaskIntoConstraints = false 

     progressView.topAnchor.constraint(equalTo: self.topAnchor).isActive = true 
     progressView.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true 
     progressView.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true 
     progressView.backgroundColor = UIColor.white 
    } 

    func updateProgress() { 
     let progressMultiplier = CGFloat(percentage/100) 

     UIView.animate(withDuration: 1.0) { 
      if let progressConstraint = self.progressBarWidth { 
       NSLayoutConstraint.deactivate([progressConstraint]) 
      } 

      self.progressBarWidth = self.progressView.widthAnchor.constraint(equalTo: self.widthAnchor, multiplier: progressMultiplier) 
      self.progressBarWidth?.isActive = true 
      self.layoutIfNeeded() 
     } 
    } 
} 

視圖控制器

class ViewController: UIViewController { 
    let progressBar: ProgressBar 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     self.view.backgroundColor = UIColor.black 

     self.view.addSubview(progressBar) 
     progressBar.translatesAutoresizingMaskIntoConstraints = false 

     progressBar.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 30).isActive = true 
     progressBar.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 30).isActive = true 
     progressBar.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -30).isActive = true 


     let button = UIButton(type: .roundedRect) 
     self.view.addSubview(button) 
     button.translatesAutoresizingMaskIntoConstraints = false 
     button.backgroundColor = UIColor.white 
     button.setTitleColor(UIColor.black, for: .normal) 
     button.setTitle("Increase 1%", for: .normal) 

     button.topAnchor.constraint(equalTo: progressBar.bottomAnchor, constant: 10).isActive = true 
     button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true 

     button.addTarget(self, action:#selector(self.buttonTapped), for: .touchUpInside) 
    } 

    required init?(coder aDecoder: NSCoder) { 
     progressBar = ProgressBar() 
     super.init(coder: aDecoder) 
    } 

    func buttonTapped() { 
     progressBar.percentage += 1 
    } 
} 

我想我初始化視圖，就像當我點擊按鈕正好儘快動畫寬度約束。

Answer 1

嘗試在layoutSubviews（）中設置動畫效果。所以像這樣的東西應該工作：

override func layoutSubviews() 
{ 
super.layoutSubviews() 
updateProgress() 
} 

Answer 2

您可以嘗試在動畫的viewController您的viewDidAppear方法的寬度約束。