基础代码

import UIKit
import WebKit

class ViewController: UIViewController,WKUIDelegate, WKNavigationDelegate {

    lazy private var webview: WKWebView = {
        self.webview = WKWebView.init(frame: self.view.bounds)
        self.webview.uiDelegate = self as WKUIDelegate
        self.webview.navigationDelegate = self as WKNavigationDelegate
        return self.webview
    }()
    
    lazy private var progressView: UIProgressView = {
        self.progressView = UIProgressView.init(frame: CGRect(x: CGFloat(0), y: CGFloat(65), width: UIScreen.main.bounds.width, height: 2))
        self.progressView.tintColor = UIColor.red
        self.progressView.trackTintColor = UIColor.white
        return self.progressView
    }()
        
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(webview)
        view.addSubview(progressView)
        webview.addObserver(self, forKeyPath: "estimatedProgress", options: .new, context: nil)
        webview.load(URLRequest.init(url: URL.init(string: "https://www.baidu.com/")!))    }
    
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        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)
                })
            }
        }
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        
    }
    deinit {
        webview.removeObserver(self, forKeyPath: "estimatedProgress")
        webview.uiDelegate = nil
        webview.navigationDelegate = nil
    }
    
}

更多代码，例如查看状态

    func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {        print("开始加载")
    }
    func webView(_ webView: WKWebView, didCommit navigation: WKNavigation!) {
        print("开始获取网页内容")
    }
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        print("加载完成")
    }
    func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {        print("加载失败")
    }
    func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction,decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
        decisionHandler(.allow);
    }