我目前正在使用Xamarin构建一个跨平台的移动的应用程序。
基本上我的应用程序只使用webview（* webview只打开一个网站，有上传图像功能 *），对于一些提取功能，我必须使用webchromeclient为Android。
添加设置webchromeclient后，webview无法从android设备打开文件选取器。（iPhone工作正常，因为webchromeclient与IOS路径无关）;
下面是我的项目的结构

---test
     |_ CustomWebView.cs
     |_ MainPage.xaml
     |_ MainPage.cs
---test.Android
     |_ MainActivity.cs
     |_ AndroidCustomWebViewRenderer.cs
---test.IOS
     |_ IOS files

CustomWebView.cs

using Xamarin.Forms;

namespace test
{
    public class CustomWebView : WebView
    {
         
    }
}

AndroidCustomWebViewRenderer.cs

[assembly: ExportRenderer(typeof(CustomWebView), typeof(CustomWebViewRenderer))]
public class CustomWebViewRenderer : WebViewRenderer
{

    public CustomWebViewRenderer(Context context) : base(context)
    {
    }

    protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)
    {
        base.OnElementChanged(e);

        if (this.Control != null)
        {
            Android.Webkit.WebView webView = this.Control;
            webView.Settings.SetGeolocationEnabled(true);

            webView.Settings.JavaScriptEnabled = true;
            webView.Settings.AllowFileAccess = true;
            webView.Settings.AllowFileAccessFromFileURLs = true;
            webView.Settings.AllowUniversalAccessFromFileURLs = true;

            webView.SetWebChromeClient(new TestWebViewClient());
          
        }
    }

    public class TestWebViewClient : Android.Webkit.WebChromeClient
    {
        
        public override bool OnShowFileChooser(Android.Webkit.WebView webView, IValueCallback filePathCallback, FileChooserParams fileChooserParams)
        {
           
            return base.OnShowFileChooser(webView, filePathCallback, fileChooserParams);

        }


        public override bool OnConsoleMessage(Android.Webkit.ConsoleMessage consoleMessage)
        {
            Log.Debug("WebViewConsole", $"{consoleMessage.Message()}");
            return base.OnConsoleMessage(consoleMessage);
        }

    }
}

MainActivity.cs

namespace test.Droid
{
    [Activity(Label = "test", Icon = "@mipmap/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize )]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
            LoadApplication(new App());
        }
        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }

    }
}

AndroidManifest.xml具有访问存储的所有权限。所以我假设webchromeclient有什么问题，从Android打开默认文件选择器时丢失了一些东西。