title: Why EvaluateJavaScriptAsync is not being executed?
body: <p>I have js function getState() that returns a css property(block or none) of an element but it isn't working, visual studio gives some Thread messages:</p>
  
  <p>09-14 23:30:22.081 W/WebView ( 6707): java.lang.Throwable: A WebView method was called on thread 'Thread-12'. All WebView methods must be called on the same thread. (Expected Looper Looper (main, tid 2) {4aca651} called on null, FYI main Looper is Looper (main, tid 2) {4aca651})
  09-14 23:30:22.081 W/WebView ( 6707):   at android.webkit.WebView.checkThread(WebView.java:2539)
  09-14 23:30:22.081 W/WebView ( 6707):   at android.webkit.WebView.evaluateJavascript(WebView.java:1054)
  Thread finished:  #4</p>
  
  <p>Can any one figure out where is the error? Also, when this be working, the returned type can be associated to a label text or it wouldn't  be a simple string?</p>
  
  <p>My code:</p>
  
  <pre><code>        public static Label label1;
          public static WebView webnav;
          StackLayout parent = null;
          public MainPage()
          {
              InitializeComponent();
              webnav = new WebView
              {
                  HeightRequest = 1000,
                  WidthRequest = 1000,
                  Source = "https://www.example.com/test.html",
  
              };
              webnav.Navigated += WebView_Navigated;
  
              label1 = new Label
              {
                  WidthRequest = 900,
                  HeightRequest = 60,
                  Text = "default text"
              };
  
              parent = new StackLayout();
              parent.Children.Add(webnav);
              parent.Children.Add(label1);
              Content = parent;
          }
  
          public void WebView_Navigated(object sender, WebNavigatedEventArgs e)
          {
              Task.Run(JSRun);
          }
  
          public static string retorno;
          public static async Task JSRun()
          {
              retorno = await webnav.EvaluateJavaScriptAsync("getState();");
          }
  </code></pre>