不带WKScriptMessage的WKWebView回调

let webView = WKWebView(frame: CGRect(x: 0, y: 0, width: 320, height: 480))
let url = URL(string: "https://www.example.com")
let request = URLRequest(url: url!)
webView.load(request)

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

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if keyPath == "title" {
        // 网页标题变化回调
        if let title = webView.title {
            print("网页标题：\(title)")
        }
    } else if keyPath == "estimatedProgress" {
        // 网页加载进度变化回调
        if let progress = webView.estimatedProgress {
            print("网页加载进度：\(progress)")
        }
    }
}