Problem when rotating android mobile screen

You should add the configChanges flag with the value keyboardHidden , orientation and screenSize in your Activity

No Xamarim

flags can be added with Android.Content.PM.ConfigChanges more or less so:

[Activity (Label = "@string/app_name", MainLauncher = true, Icon="@drawable/launcher",
    ConfigurationChanges = ConfigChanges.KeyboardHidden | ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
public class MainActivity : ...

No Manifest.xml

I'm not sure if Xamarin provides control over the generated Manifest.xml, but if it makes available to the <activity> tag, add android:configChanges="keyboardHidden|orientation|screenSize" , for example:

<application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
    <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar"
            android:configChanges="keyboardHidden|orientation|screenSize">

Saving Instances

I do not know if this is necessary for Xamarin (or if it depends on a newer version of Android), but if the previous configuration is not enough then save the instances:

If you are in CSharp

Add to methods (or create them) with override :

private WebView minhaWebView; //Se a sua webView nesta variável

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);
    ...
}

protected override void OnSaveInstanceState(Bundle outState)
{
    base.OnSaveInstanceState(outState); //Salva Activity
    minhaWebView.SaveState(outState);   //Salva WebView
}

protected override void OnRestoreInstanceState(Bundle savedInstanceState)
{
    base.OnRestoreSaveInstanceState(savedInstanceState); //Restaura o Activity
    minhaWebView.RestoreState(savedInstanceState);       //Restaura o WebView
}

If you are in Java

private WebView minhaWebView; //Defina a webView nesta variável

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ...
}

@Override
protected void onSaveInstanceState(Bundle outState){
    super.onSaveInstanceState(outState); //Salva Activity
    minhaWebView.saveState(outState);    //Salva WebView
}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState){
    super.onRestoreInstanceState(savedInstanceState); //Restaura o Activity
    minhaWebView.restoreState(savedInstanceState);    //Restaura o WebView
}

Xamarin Documentation

• Android.App.Activity.OnCreate >
• Android.App.Activity.OnSaveInstanceState
• Android.App.Activity.OnRestoreInstanceState >

Activities on Android are destroyed and re-created when the screen rotates. You need to save the required data in a Bundle before it is destroyed in the onSaveInstanceState () method and then restore the Bundle data in OnCreate if it is not null.

More details here: link

To complement, a shortcut you can turn to is the use of setRetainInstance (true) ;, so your problems with persistence when your activity or fragment is destroyed will be resolved in part. xD