SwiftUI WKWebView 带进度条

SwiftUI 暂时没有相应的WebView组件，只能用UIKit来实现WebView功能。
要实现加载进度条，目前有两种方法：

1. UIViewRepresentable 包装， 加载正常，返回再次进来崩溃

struct CoscoWebView: UIViewRepresentable {
    typealias UIViewType = WKWebView
    
    let urlString: String?
    
    @State var webView = WKWebView()
    @Binding var progress: Float
    
    func makeUIView(context: Context) -> WKWebView {
        context.coordinator.addProgressObserver()
        
        let config = WKWebViewConfiguration()
        // 不做此配置设置, 大多数网页是可以正常打开的
        // 但对于百度官网，会出现手机可以打开而ipad白屏（不断的在代理方法didStart 和 didFinish之间循环）
        config.defaultWebpagePreferences.preferredContentMode = .mobile
        
        let wk = WKWebView(frame: UIScreen.main.bounds, configuration: config)
        wk.navigationDelegate = context.coordinator
        webView = wk
        return webView
    }
    
    func updateUIView(_ uiView: WKWebView, context: Context) {
        if let safeString = urlString {
            // 路径中出现某些特殊字符（如 = 等...），会返回nil，此处需要编码
            if let url = URL(string: safeString.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) ?? "") {
                let request = URLRequest(url: url)
                uiView.load(request)
            }
        }
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
}

extension CoscoWebView {
    
    class Coordinator: NSObject, WKNavigationDelegate {
        
        var parent: CoscoWebView

        init(_ parent: CoscoWebView) {
            self.parent = parent
        }
        
        func addProgressObserver() {
            parent.webView.addObserver(self, forKeyPath: #keyPath(WKWebView.estimatedProgress), options: .new, context: nil)
        }
        
        override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
            if let o = object as? WKWebView, o == parent.webView {
                if keyPath == #keyPath(WKWebView.estimatedProgress) {
                    self.parent.progress = Float(parent.webView.estimatedProgress)
                }
            }
        }
        
        func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
            print("开始加载")
        }
        
        func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
            print(error)
        }
                
        func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
            print("web 加载完成")
        }
        
    }
}

2. 用ViewController 添加WKWebView，再用UIViewControllerRepresentable包装

class WebController: UIViewController, WKNavigationDelegate {
    
    var path: String?
    var webView = WKWebView()
    var line = UIView() // 进度条线
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let config = WKWebViewConfiguration()
        config.defaultWebpagePreferences.preferredContentMode = .mobile
        webView = WKWebView(frame: UIScreen.main.bounds, configuration: config)
        webView.navigationDelegate = self
        self.view.addSubview(webView)
        
        // 监听加载进度
        self.webView.addObserver(self, forKeyPath: #keyPath(WKWebView.estimatedProgress), options: .new, context: nil)
        
        // 进度条
        line = UIView(frame: CGRect(x: 0, y: 0, width: 110, height: 10))
        line.backgroundColor = UIColor.blue
        self.view.addSubview(line)
    }

    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        
        if let web = object as? WKWebView, web == self.webView {
            line.frame.size.width = (web.estimatedProgress) * web.frame.size.width
        }
    }
    
    func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
        print("开始加载web")
    }
    
    func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
        print("加载失败-：", error.localizedDescription.description)
        self.line.removeFromSuperview()
    }
    
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        print("加载成功~")
        self.line.removeFromSuperview()
    }
}

struct XWWebView: UIViewControllerRepresentable {
    typealias UIViewControllerType = WebController
    
    var path: String?

    func makeUIViewController(context: Context) -> WebController {
        let c = WebController()
        c.path = path
        return WebController()
    }
    
    func updateUIViewController(_ uiViewController: WebController, context: Context) {
        guard let url = path else { return }
        let request = URLRequest(url: URL(string: url)!)
        uiViewController.webView.load(request)

    }
}