How to access the elements of a ControlTemplate in Xamarin Forms

Question

I have a ControlTemplate defined in App.xaml. Now, I need to be able to handle certain UI events. In Visual Studio's XAML editor, if I attach a handler to an event, the handler is created in App.xaml.cs. However, I need to do this in pages that use this control template.

I'm thinking the only way is to iterate through the elements in the control template and find the right element and create handlers in pages. However, I'm not sure how to access the elements from the ControlTemplate object.

Does Xamarin provide a way to peek into the contents of a ControlTemplate?

Answer 1

If you have Page instance you can cast it to IPageController and it's InternalChildren property contains controls from the template.

Here is an extension method I'm using to find controls by name

public static T FindTemplateElementByName<T> (this Page page, string name)
    where T: Element
{
    var pc = page as IPageController;
    if (pc == null)
    {
        return null;
    }

    foreach (var child in pc.InternalChildren)
    {
        var result = child.FindByName<T> (name);
        if (result != null)
        {
            return result;
        }
    }

    return null;
}

Answer 2

I havent found a way yet to iterate through the control template children. I used template binding https://developer.xamarin.com/guides/xamarin-forms/templates/control-templates/template-binding/ to bind to a command object, the properties for the commands are defined in my base page, then used a base view to define my commands and set them to the binding backing properties in the basepage OnAppearing override.

I am working on a blog entry and will update this when I have code to show.