Xamarin.Forms: XAML property pass-through - xamarin.forms

Question

How do I pass property values to custom control children without writing code?
Content page:
<views:ButtonView Image="newViolationSmall.png" Text="{Binding ParentsText}/>
Then ButtonView.xaml
<StackLayout
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="SmartwebsCrossPlatform.Portable.Views.ButtonView">
<Button Image="{Binding Image}"/>
<Label Text="{Binding Text}" />
</StackLayout>
And ButtonView.cs
public partial class ButtonView : StackLayout {
...
//text
public static readonly BindableProperty TextProperty = BindableProperty.Create( "Text", typeof( string ), typeof( ButtonView ), null, BindingMode.Default, null, null, null, null );
public string Text {
get {
return (string)GetValue( TextProperty );
}
set {
SetValue( TextProperty, value );
}
}
//image
public static readonly BindableProperty ImageProperty = BindableProperty.Create( "Image", typeof( string ), typeof( ButtonView ) );
public string Image {
get {
return (string)GetValue( ImageProperty );
}
set {
SetValue( ImageProperty, value );
}
}
This does not show any text or image. A rather annoying alternative is to name both Button and Label, override ButtonView.OnPropertyChanged, and explicitly set their properties from code but it causes a System.ObjectDisposedException (Object name: 'Android.Graphics.Bitmap') when I navigate around this page.
#yyou's solution works for const values, but not for parent's properties.

Answer 1

The only thing missing is to set the BindingContext of this custom layout.
ie.
//ButtonView.xaml.cs
public ButtonView ()
{
InitializeComponent ();
BindingContext = this;
}
//to use this ButtonView component in a page
//ie. DetailPage.xaml
<ContentPage ...>
<app2:ButtonView Text="{Binding ParentText}" Image="{Binding ButtonImage }"/>
</ContentPage>
//in DetailPage.xaml.cs
public DetailPage() {
InitializeComponent ();
BindingContext = new DetailViewModel() {
ParentText = "sjldfdkfdjd",
ButtonImage = "my-button-image.png"
};
}
//in the file DetailViewModel.cs
namespace App2.ViewModels
{
public class DetailViewModel : BaseViewModel {
private string _parentText;
public string ParentText {
get { return _parentText; }
set { SetProperty<string>(ref _parentText, value); }
}
private string _buttonImage;
public string ButtonImage {
get { return _buttonImage; }
set { SetProperty<string>(ref _buttonImage, value); }
}
//other stuff
}
}