[Android] add Element and Element Property Changed hooks for ImageButton

[PureWeen]

Description of Change

ImageButton Renderer for Android didn't provide overrides that are consistent with other renderers for hooking into element and element property change events

API Changes

Added the following methods to the ImageButtonRenderer

protected virtual void OnElementChanged(ElementChangedEventArgs<ImageButton> e);
protected virtual void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e);

Platforms Affected

• Android

Testing Procedure

Add a custom ImageButtonRenderer for Android

PR Checklist

• Has automated tests
• Rebased on top of the target branch at time of PR
• Changes adhere to coding standard

[StephaneDelcroix]

make the virtual method empty. think about your future children

[StephaneDelcroix]

it's better to keep the virtual void OnElementChanged empty and invokes it after firing the event

[PureWeen]

I mainly did it like this because this is how VisualElementRenderer does it
https://github.com/xamarin/Xamarin.Forms/blob/master/Xamarin.Forms.Platform.Android/VisualElementRenderer.cs#L305

So I just copied that one for the sake of consistency

[samhouts]

I suppose it's possible for someone to want to control when (or whether) to invoke ElementChanged when they override OnElementChanged.

[PureWeen]

For the record I do agree with @StephaneDelcroix

But I did it this way because this is the same way we do it literally everywhere that I could find. So I feel like at this point consistency should be the winner

https://github.com/xamarin/Xamarin.Forms/blob/master/Xamarin.Forms.Platform.iOS/Renderers/WkWebViewRenderer.cs#L126

[samhouts]

Yeah, agreed. Consistency is best. :/

[StephaneDelcroix]

Yeah, agreed. Consistency is best. :/

disagreed, but I'm not going to die on this hill