c# - 在 Xamarin Android App 中使用 webview 上传文件

Question

我正在开发一个简单的 xamarin android 应用程序，它允许显示响应式网站并接收推送通知。

Webview 似乎对 Xamarin 有一些限制，因此我根据以下评论 (https://github.com/GabLeRoux/xamarin-android-webview-upload) 使用了以下解决方法 (https://forums.xamarin.com/discussion/3259/cannot-override-webviewclient-class-for-file-upload-support)，以便让 html 上传按钮按预期工作。

一切顺利，直到我将推送通知从 GCM 迁移到 FCM。在 webview 之后，返回开始工作。

基本上，html 上传按钮不会打开文件选择器对话框，也不会引发任何错误。它什么都不做。

以下是我在网络事件中使用的代码。

我正在使用 Xamarin.Android 7.3 和 VS 2015。

欢迎任何帮助。

using System;
using Android.Runtime;
using Android.Views;
using Android.App;
using Android.Content;
using Android.OS;

using Android.Webkit;
using Android.Widget;



namespace sigese
{
    [Activity(Label = "WebActivity")]
    public class WebActivity : Activity
    {


        IValueCallback mUploadMessage;
        private static int FILECHOOSER_RESULTCODE = 1;
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.WebLayout);

            ActionBar.Hide();

            var username = Intent.GetStringExtra("username");
            var password = Intent.GetStringExtra("password");

            var chrome = new FileChooserWebChromeClient((uploadMsg, acceptType, capture) => {
                mUploadMessage = uploadMsg;
                var i = new Intent(Intent.ActionGetContent);
                i.AddCategory(Intent.CategoryOpenable);
                i.SetType("image/*");
                StartActivityForResult(Intent.CreateChooser(i, "File Chooser"), FILECHOOSER_RESULTCODE);
            });

            var webview = this.FindViewById<WebView>(Resource.Id.LocalWebView);
            webview.SetWebViewClient(new WebViewClient());
            webview.SetWebChromeClient(chrome);
            webview.Settings.JavaScriptEnabled = true;


           webview.LoadUrl("https://example.com/login.asp?username="+username+"&password="+password);




        }

        protected override void OnActivityResult(int requestCode, Result resultCode, Intent intent)
        {
            if (requestCode == FILECHOOSER_RESULTCODE)
            {
                if (null == mUploadMessage)
                    return;
                Java.Lang.Object result = intent == null || resultCode != Result.Ok
                    ? null
                    : intent.Data;
                mUploadMessage.OnReceiveValue(result);
                mUploadMessage = null;
            }
        }

        public override void OnBackPressed()
        {
            WebView localWebView = FindViewById<WebView>(Resource.Id.LocalWebView);
            if (localWebView.CanGoBack())
            {
                localWebView.GoBack();
            }
            else
            {
               return;
            }
        }


    }
    partial class FileChooserWebChromeClient : WebChromeClient
    {
        Action<IValueCallback, Java.Lang.String, Java.Lang.String> callback;

        public FileChooserWebChromeClient(Action<IValueCallback, Java.Lang.String, Java.Lang.String> callback)
        {
            this.callback = callback;
        }

        // For Android < 5.0
        [Java.Interop.Export]
        public void openFileChooser(IValueCallback uploadMsg, Java.Lang.String acceptType, Java.Lang.String capture)
        {
            callback(uploadMsg, acceptType, capture);
        }

        // For Android > 5.0

    }
}

Answer 1

第一步

文件上传可以，我们需要在 android manifest 中授予读/写权限。在主 Activity.cs 中

第二步

private Action<int, Result, Intent> resultCallbackvalue;

public void StartActivity(Intent intent, int requestCode, Action<int, Result, Intent> resultCallback)
{
    this.resultCallbackvalue = resultCallback;
    StartActivityForResult(intent, requestCode);
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
    base.OnActivityResult(requestCode, resultCode, data);
    if (this.resultCallbackvalue != null)
{
   this.resultCallbackvalue(requestCode, resultCode, data);
   this.resultCallbackvalue = null;
}

第三步

添加ExtendedChromeClient，cs继承自:WebChromeClient

private static int filechooser = 1;
private IValueCallback message;
private MainActivity activity = null;

public ExtendedChromeClient(MainActivity context)
{
    this.activity = context;
}

public override bool OnShowFileChooser(WebView webView, IValueCallback filePathCallback, FileChooserParams fileChooserParams)
{
    this.message = filePathCallback;
    Intent chooserIntent = fileChooserParams.CreateIntent();
    chooserIntent.AddCategory(Intent.CategoryOpenable);
    this.activity.StartActivity(Intent.CreateChooser(chooserIntent, "File Chooser"), filechooser, this.OnActivityResult);
    return true;
}

private void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
    if (data != null)
    {
        if (requestCode == filechooser)
        {
            if (null == this.message)
            {`enter code here`
                    return;
            }

            this.message.OnReceiveValue(WebChromeClient.FileChooserParams.ParseResult((int)resultCode, data));
            this.message = null;
        }
    }
}