Custom Renderers & Effects

Custom Renderers

Custom renderers allow the Generic Xamarin.Forms control to be customized in behavior and look as per the platform they are going to be used on. This enables developers to give a native look and behavior to the otherwise Generic Xamarin.Forms Control.

Xamarin Forms controls are NOT rendered directly on the native platform. Every Xamarin.Forms control has an accompanying renderer for each platform that creates an instance of a native control. The properties from the Xamarin Forms control are translated across to the native control, then the native control is placed in the native layout, which then gets rendered by the platform.

Custom Renderers allow developers to customize the appearance and/or behavior of the control by writing their custom classes. Custom Renderers can be defined to have a custom behavior or appearance for one platform while allowing the default behavior on other platforms or they can be defined for each platform and provide customization for each different platform like iOS, Android, and the Universal Windows Platform (UWP). If instead of changing the complete behavior and appearance only some trivial changes are required then 'Effects' can be used as an alternative.

Effects

Effects, like Custom Renderers, allow a developer to customize controls for a specific platform. Effects are preferred over Custom Renderers when small styling changes are required instead of a complete layout or behavior change. Custom Effects are created for platform-specific projects by extending the base class PlatformEffect. Once created, they can be attached to the control it is meant for.

Effects don't have any type related information about the control they are attached to and hence if they are specified with a wrong control they should gracefully degrade. Effects are reusable and can be parameterised to extend its reusability.

Eg The sample application demonstrates a Focus Effect that changes the background color of a control when it gains focus.