Another way might be something like:

within your shared project

create an Inteface called IKeyboardListener that is public

Within the page's code behind (or viewmodel) where you want to listen for code event add the following:

MessagingCenter.Subscribe<IKeyboardListener, string>(this, "KeyboardListener", (sender, args) => {
    Debug.WriteLine(args);
});

in UWP's App.xaml.cs

at the top add:
using forms = Xamarin.Forms;

add the interface to your sealed class:

sealed partial class App : Application, IKeyboardListener
{
...etc

Add this line to the end of the OnLaunced:

protected override void OnLaunched(LaunchActivatedEventArgs e)
{
    ...
// very last line
    Windows.UI.Core.CoreWindow.GetForCurrentThread().KeyDown += HandleKeyDown;
 }

add this method somewhere in the class:

 public void HandleKeyDown(Windows.UI.Core.CoreWindow window, Windows.UI.Core.KeyEventArgs e)
 {
    forms.MessagingCenter.Send<IKeyboardListener, string>(this, "KeyboardListener", e.VirtualKey.ToString());
 }

Conclusion

You can implement similar methods within other native projects. Like with Android

Android is easier because you can tap into the OnKeyUp (or Down) events right from within MainActivity:

    public override bool OnKeyUp(Keycode keyCode, KeyEvent e)
        {
            forms.MessagingCenter.Send<IKeyboardListener, string>(this, "KeyboardListener", keyCode.ToString());
        }

I'm not sure if this has any drawbacks other than maybe unsubscribing to the MessagingCenter listener in the case of Android but it appears to work.

I found a solution, if someone needs it, here is the code of the custom renderer for iOS:

class HtmlLabelRenderer : ViewRenderer<Label, UITextView>
    {
        protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
        {
            base.OnElementChanged(e);

            var view = (HtmlLabel)Element;
            if (view == null) return;

            UITextView textView = new UITextView(new CGRect(0, 0, view.Width, view.Height));
            textView.Text = view.Text;
            textView.Font = UIFont.SystemFontOfSize((float)view.FontSize);
            textView.Editable = false;
            textView.Bounces = false;

            // Setting the data detector types mask to capture all types of link-able data
            textView.DataDetectorTypes = UIDataDetectorType.All;
            textView.BackgroundColor = UIColor.Clear;

            // overriding Xamarin Forms Label and replace with our native control
            SetNativeControl(textView);
        }
}

Deprecated .

       public static readonly BindableProperty ProgressValueProperty =
            BindableProperty.Create<MyControl, double>
       (p => p.Value, double.NaN, BindingMode.TwoWay, propertyChanged: (bindable, oldValue, newValue) =>
       {
           var control = (MyControl)bindable;
           control.Value = newValue;
       });

New version:

 public static readonly  BindableProperty ProgressValueProperty = BindableProperty.Create("Value", typeof(double), 
 typeof(MyControl), double.NaN, BindingMode.TwoWay, null, propertyChanged: OnItemsSourceChanged);
  static void OnItemsSourceChanged(BindableObject bindable, object oldValue, object newValue)
    {
        var control = (MyControl)bindable;
        control.Value = (double)newValue;
    }

try this

webviewpage.xaml:

<WebView x:Name="WebViewItem"
                  Navigated="OnNavigated">
</WebView>

webviewpage.xaml.cs:

private void OnNavigated(object sender, WebNavigatedEventArgs e)
{
    IsBusy = false;
    Indicator.IsVisible = false;
}

Hi,

you should use the x:Key Property to assign a valid key to your style. The x:Name Attribute isn't needed here.

So your code should look like:

<Application.Resources>
        <ResourceDictionary>
            <!-- omitted irrelevant parts -->

            <Style TargetType="StackLayout" x:Key="VerticalStack">
                <Setter Property="Orientation" Value="Vertical"/>
                <Setter Property="Spacing" Value="16"/>
            </Style>

            <Style x:Key="FormFirstPortraitStyle" TargetType="StackLayout" BasedOn="{StaticResource VerticalStack}">
                <Setter Property="HorizontalOptions" Value="Center"/>
                <Setter Property="VerticalOptions" Value="Start"/>
                <Setter Property="Margin" Value="16, 100, 16, 16"/>
            </Style>

            <Style x:Key="FormFirstLandscapeStyle" TargetType="StackLayout" BasedOn="{StaticResource VerticalStack}">
                <Setter Property="HorizontalOptions" Value="Center"/>
                <Setter Property="VerticalOptions" Value="Center"/>
                <Setter Property="Margin" Value="16, 16, 16, 16"/>
            </Style>
        </ResourceDictionary>
    </Application.Resources>

Although I can do the following in code, I want to do it in Xaml:

            if (Xamarin.Forms.Device.Idiom == TargetIdiom.Phone)
            {
                MainPage = new NavigationPage(new MyPage());
            }
            else if(Xamarin.Forms.Device.Idiom == TargetIdiom.Tablet)
            {
        // etc
            }
            else if(Xamarin.Forms.Device.Idiom == TargetIdiom.Desktop)
            {
        // etc
            }
            else if (Xamarin.Forms.Device.Idiom == TargetIdiom.Unsupported)
            {
                // etc
            }
            else
            {
                // etc
            }

Another post suggests the following, however it throws an error "OnIdiom" not found in xmlns: http://xamarin.com/schemas/2014/forms:

<StackLayout>
    <StackLayout.Orientation>
    <OnIdiom x:TypeArguments="StackOrientation">
        <OnIdiom.Phone>Vertical</OnIdiom.Phone>
        <OnIdiom.Tablet>Horizontal</OnIdiom.Tablet>
    </OnIdiom>
    </StackLayout.Orientation>
    <Label Text="child0"/>
    <Label Text="child1"/>          
</StackLayout>

Any ideas as to how to do this in Xaml?