Xamarin Forms - Xaml Element injected to every page

Question

I am looking for a way to have an element (DXPopup) injected to every page while using Xamarin Forms Shell.

My initial thought would be to create a custom renderer for Tabbar and inject the popup above the tabbar. But I hit a blocker when my tabs are contained in a FlyoutItem. I then thought about a custom renderer for ContentView and add a child element, though hit a blocker where Android wanted an android view.

How would be best to tackle this issue?

Desired outcome: DXpopup element added to every page, so we can call a common show method (by message of mediator class)

Answer 1

I solved this using Jason's suggested route above:

Basepage - that had a control template Control Template like:

<ControlTemplate x:Key="BasePageTemplate">
        <StackLayout VerticalOptions="FillAndExpand">
            //your element (in my case a DXPopup
            <ContentPresenter VerticalOptions="FillAndExpand"/>
        </StackLayout>
</ControlTemplate>

Register to the binding context changing (in code behind of base page): BindingContextChanged += SetBindingContext;

This was to update to the consuming pages viewmodel.

Said viewmodel would have a baseViewmodel, where I registered the element injected like so:

private void SetBindingContext(object sender, EventArgs e)
    {
        if (BindingContext is not ViewModelBase baseVM) return;

        var dxPopUp = GetTemplateChild("ElementName");
        baseVM.DxPopUp = dxPopUp as DXPopup;
    }

This in turn allowed me to use the viewmodel base to interact with the element (in my case showing it)