在SwiftUI中加载网站时加载活动指示器

import SwiftUI
import WebKit

struct WebView: UIViewRepresentable {
    let url: URL
    
    func makeUIView(context: Context) -> WKWebView {
        let webView = WKWebView()
        webView.load(URLRequest(url: url))
        webView.addObserver(context.coordinator, forKeyPath: #keyPath(WKWebView.isLoading), options: .new, context: nil)
        return webView
    }
    
    func updateUIView(_ uiView: WKWebView, context: Context) {
        // 更新WebView的内容
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator()
    }
    
    class Coordinator: NSObject {
        // 监听WebView的isLoading属性，显示/隐藏活动指示器
        override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
            if keyPath == #keyPath(WKWebView.isLoading) {
                if let webView = object as? WKWebView {
                    if webView.isLoading {
                        // 显示活动指示器
                    } else {
                        // 隐藏活动指示器
                    }
                }
            }
        }
    }
}

struct ContentView: View {
    var body: some View {
        VStack {
            WebView(url: URL(string: "https://www.example.com")!)
                .frame(height: 300)
            // 其他视图
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}