How can I share the value of a field between back-end C# and a renderer? - xamarin

Question

My C# looks like this:
public App()
{
InitializeComponent();
MainPage = new Japanese.MainPage();
}
public partial class MainPage : TabbedPage
{
public MainPage()
{
InitializeComponent();
var phrasesPage = new NavigationPage(new PhrasesPage())
{
Title = "Play",
Icon = "ionicons-2-0-1-ios-play-outline-25.png"
};
public partial class PhrasesPage : ContentPage
{
public PhrasesFrame phrasesFrame;
public PhrasesPage()
{
InitializeComponent();
NavigationPage.SetHasNavigationBar(this, false);
App.phrasesPage = this;
}
protected override void OnAppearing()
{
base.OnAppearing();
App.dataChange = true;
phrasesFrame = new PhrasesFrame(this);
phrasesStackLayout.Children.Add(phrasesFrame);
}
public partial class PhrasesFrame : Frame
{
private async Task ShowCard()
{
if (pauseCard == false)
..
and I have an iOS renderer for a tab page
public class TabbedPageRenderer : TabbedRenderer
{
private MainPage _page;
private void OnTabBarReselected(object sender, UITabBarSelectionEventArgs e)
{
...
pauseCard = false;
...
My problem is there is no connection between the two and I would like to know how I can make it so that pauseCard could be set in one place and read in another.

Answer 1

Here is a simple custom Entry example using a bindable bool property that gets changed from the renderer every time the text changes in the entry.
Entry subclass w/ a bindable property called OnOff (bool)
public class CustomPropertyEntry : Entry
{
public static readonly BindableProperty OnOffProperty = BindableProperty.Create(
propertyName: "OnOff",
returnType: typeof(bool),
declaringType: typeof(CustomPropertyEntry),
defaultValue: false);
public bool OnOff
{
get { return (bool)GetValue(OnOffProperty); }
set { SetValue(OnOffProperty, value); }
}
}
iOS Renderer
Note: I keep a reference to the instance of the CustomPropertyEntry passed into OnElementChanged so later I can set its custom property when needed.
public class CustomPropertyEntryRenderer : ViewRenderer<CustomPropertyEntry, UITextField>
{
UITextField textField;
CustomPropertyEntry entry;
protected override void OnElementChanged(ElementChangedEventArgs<CustomPropertyEntry> e)
{
base.OnElementChanged(e);
if (Control == null)
{
textField = new UITextField();
SetNativeControl(textField);
}
if (e.OldElement != null)
{
textField.RemoveTarget(EditChangedHandler, UIControlEvent.EditingChanged);
entry = null;
}
if (e.NewElement != null)
{
textField.AddTarget(EditChangedHandler, UIControlEvent.EditingChanged);
entry = e.NewElement;
}
}
void EditChangedHandler(object sender, EventArgs e)
{
entry.OnOff = !entry.OnOff;
}
}
XAML Example:
<local:CustomPropertyEntry x:Name="customEntry" Text="" />
<Switch BindingContext="{x:Reference customEntry}" IsToggled="{Binding OnOff}" />