Xamarin.macOS自定义CustomWebView的Navigated事件未触发如何解决

问题根因 #

你当前使用了默认的空WKNavigationDelegate实例，该实例没有实现WKWebView的导航回调方法，也没有将原生导航事件映射到自定义CustomWebView的Navigated事件上，所以事件无法触发，同时代码中存在重复赋值NavigationDelegate的无效逻辑。

实现代码 #

第一步：自定义WKNavigationDelegate子类 #

该子类负责接收原生WKWebView的导航回调，并映射到CustomWebView的对应事件：

public class CustomWebViewNavigationDelegate : WKNavigationDelegate
{
    private readonly CustomWebView _customWebView;

    public CustomWebViewNavigationDelegate(CustomWebView webView)
    {
        _customWebView = webView;
    }

    // 页面开始加载时触发，对应CustomWebView的Navigating事件
    public override void DidStartProvisionalNavigation(WKWebView webView, WKNavigation navigation)
    {
        base.DidStartProvisionalNavigation(webView, navigation);
        var args = new WebNavigatingEventArgs(WebNavigationEvent.NewPage, 
            new UrlWebViewSource { Url = webView.Url?.AbsoluteString }, 
            webView.Url?.AbsoluteString);
        _customWebView.SendNavigating(args);
    }

    // 页面加载完成时触发，对应CustomWebView的Navigated事件
    public override void DidFinishNavigation(WKWebView webView, WKNavigation navigation)
    {
        base.DidFinishNavigation(webView, navigation);
        var args = new WebNavigatedEventArgs(WebNavigationEvent.NewPage, 
            new UrlWebViewSource { Url = webView.Url?.AbsoluteString }, 
            webView.Url?.AbsoluteString, 
            WebNavigationResult.Success);
        _customWebView.SendNavigated(args);
    }

    // 页面加载失败时触发
    public override void DidFailNavigation(WKWebView webView, WKNavigation navigation, NSError error)
    {
        base.DidFailNavigation(webView, navigation, error);
        var args = new WebNavigatedEventArgs(WebNavigationEvent.NewPage, 
            new UrlWebViewSource { Url = webView.Url?.AbsoluteString }, 
            webView.Url?.AbsoluteString, 
            WebNavigationResult.Failure);
        _customWebView.SendNavigated(args);
    }

    // provisional阶段导航失败时触发
    public override void DidFailProvisionalNavigation(WKWebView webView, WKNavigation navigation, NSError error)
    {
        base.DidFailProvisionalNavigation(webView, navigation, error);
        var args = new WebNavigatedEventArgs(WebNavigationEvent.NewPage, 
            new UrlWebViewSource { Url = webView.Url?.AbsoluteString }, 
            webView.Url?.AbsoluteString, 
            WebNavigationResult.Failure);
        _customWebView.SendNavigated(args);
    }
}

第二步：修改CustomWebView类 #

在你的CustomWebView类中添加方法，暴露内部的事件触发逻辑：

public class CustomWebView : WebView
{
    // 保留你原来的CustomUserAgent等自定义属性

    public void SendNavigating(WebNavigatingEventArgs args)
    {
        OnNavigating(args);
    }

    public void SendNavigated(WebNavigatedEventArgs args)
    {
        OnNavigated(args);
    }
}

第三步：修改自定义Renderer代码 #

替换原来的空WKNavigationDelegate，删掉重复赋值逻辑：

[assembly: ExportRenderer(typeof(CustomWebView), typeof(CustomWebViewRenderer))]
namespace DesktopClient.MacOS.CustomRenderers
{
    public class CustomWebViewRenderer : ViewRenderer<CustomWebView, WKWebView>
    {
        private WKWebView wkWebView;

        protected override void OnElementChanged(ElementChangedEventArgs<CustomWebView> e)
        {
            base.OnElementChanged(e);            

            if (Control == null)
            {
                WKWebViewConfiguration config = new WKWebViewConfiguration();                
                wkWebView = new WKWebView(Frame, config)
                {
                    // 使用自定义的NavigationDelegate
                    NavigationDelegate = new CustomWebViewNavigationDelegate(e.NewElement)
                };
                SetNativeControl(wkWebView);
                WKWebViewContainer.WKWebView = wkWebView;
            }

            if (e.NewElement != null)
            {
                if (e.NewElement.Source is UrlWebViewSource source && !string.IsNullOrEmpty(source.Url))
                {
                    Control.LoadRequest(new NSUrlRequest(new NSUrl(source.Url)));
                }
                Control.CustomUserAgent = e.NewElement.UserAgent;
            }
        }
    }
}

注意事项 #

• 如果需要处理跨域请求、权限申请、跳转拦截等逻辑，可在CustomWebViewNavigationDelegate中重写对应的WKNavigationDelegate方法实现。
• 如出现内存泄漏问题，可将Delegate中的_customWebView改为弱引用持有。
• 若使用MAUI框架，更推荐使用Handler替代自定义Renderer实现，逻辑与上述映射思路一致。

内容的提问来源于stack exchange，提问作者Max951