Xamarin Forms WebView Crashes for Android when used with Forms Embedding

Question

I have created a simple forms Content Page with a WebView in it. It points to "www.google.com". I tried Forms Embedding to start the Forms page from Android as a Fragment and as a ViewController in iOS. It works fine in iOS however it crashes in Android with the following error on the line where I create the fragment: Value cannot be null. Parameter name: startActivityForResult

The Code for android is shown below:

`    
BaseActivity mainActivity = (BaseActivity)Activity;
FragmentManager fragmentManager = mainActivity.CurrentFragmentManager();
Forms.Init(mainActivity, null);
Fragment webViewPage = new WebViewPage().CreateFragment(mainActivity);
fragmentManager.BeginTransaction().Replace(Resource.Id.accountHelp_container, webViewPage, "Webview").AddToBackStack(null).Commit();`

Any Idea what I could be Doing wrong.

York Shen · Accepted Answer · 2017-11-01 12:53:13Z

Xamarin Forms WebView Crashes for Android when used with Forms Embedding

I reproduced your problem when I transfer a Xamarin.Forms Page(which contain a WebView) to Fragment, and here is a workaround :

You could put a native android Android.Webkit.WebView in a Fragment, then you could display this Fragment to implement the same feature.

Create a WebViewFragment :

public class WebViewFragment : Fragment
{
    public override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

    }

    public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        var view = inflater.Inflate(Resource.Layout.webview_in_fg, container, false);
        WebView fg_webview = view.FindViewById<WebView>(Resource.Id.fg_webview);
        fg_webview.SetWebViewClient(new MyWebViewClient());

        fg_webview.Settings.JavaScriptEnabled = true;
        fg_webview.LoadUrl("http://developer.xamarin.com");

        return view;
    }
}

public class MyWebViewClient : WebViewClient
{
    public override bool ShouldOverrideUrlLoading(WebView view, string url)
    {
        view.LoadUrl(url);
        return true;
    }

    public override void OnPageStarted(WebView view, string url, Android.Graphics.Bitmap favicon)
    {
        base.OnPageStarted(view, url, favicon);
    }

    public override void OnPageFinished(WebView view, string url)
    {
        base.OnPageFinished(view, url);
    }

    public override void OnReceivedError(WebView view, ClientError errorCode, string description, string failingUrl)
    {
        base.OnReceivedError(view, errorCode, description, failingUrl);
    }
}

Create a WebView layout :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <WebView
        android:id="@+id/fg_webview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</RelativeLayout>

Replace your WebViewPage with the WebViewFragment :

//Fragment webViewPage = new WebViewPage().CreateFragment(mainActivity);
Fragment webViewPage = new WebViewFragment();

Shen. Thanks for the Solution. It worked perfectly. The reason we were using a forms webview to have the same functionality on iOS as well. Now because of this bug, we have to implement the same functionality twice in the native code. Any Suggestions regarding that will be great. Thanks again :)

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