Swift WKWebView 通过监听，获取加载进度和标题

WKWebView提供了可以监听页面加载进度，以及页面的标题的方法。

let webView = WKWebView(frame: CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight - navigationHeight ), configuration: WKWebViewConfiguration())
    
lazy private var progressView: UIProgressView = {
        let progress = UIProgressView.init(frame: CGRect(x: CGFloat(0), y: CGFloat(0), width: UIScreen.main.bounds.width, height: 2))
        progress.tintColor = UIColor.green
        progress.trackTintColor = UIColor.white
        return progress
    }()

override func viewDidLoad() {

    webView.addObserver(self, forKeyPath: "title", options: .new, context: nil)
    webView.addObserver(self, forKeyPath: "estimatedProgress", options: .new, context: nil)

}

//添加观察者方法
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        
        //设置进度条
        if keyPath == "estimatedProgress"{
            progressView.alpha = 1.0
            progressView.setProgress(Float(webView.estimatedProgress), animated: true)
            if webView.estimatedProgress >= 1.0 {
                UIView.animate(withDuration: 0.3, delay: 0.1, options: .curveEaseOut, animations: {
                    self.progressView.alpha = 0
                }, completion: { (finish) in
                    self.progressView.setProgress(0.0, animated: false)
                })
            }
        }
            
       //重设标题
        else if keyPath == "title" {
            self.title = self.webView.title
        }
    }