Xamarin：重用效果

Question

I have the following

PlatformEffect Android Project

public class LabelShadowEffect : PlatformEffect
{
   protected override void OnAttached()
   {
      ...
   }

   protected override void OnDetached()
   {
      ...
   }
}

RoutingEffect .NetStandard Lib

public class ShadowEffect : RoutingEffect
{
   ...
}

Xaml

<controls:FontAwesomeLabel

  ...

  <controls:FontAwesomeLabel.Effects>
     <effects:ShadowEffect
        DistanceX="2"
        DistanceY="2"
        Radius="2"
        Color="{StaticResource HeaderTextShadowColor}" />
  </controls:FontAwesomeLabel.Effects>
</controls:FontAwesomeLabel>

This works fine, though it would be nice to be able to reuse this as a static resource. So, i notice a can set the property Element.Effects , its defined as follows

public System.Collections.Generic.IList<Xamarin.Forms.Effect> Effects { get; }

I would have thought i could just write a xaml List or an array and put it in a resource and reuse it

ie

Effects="{StaticResource StandardShadowEffect}"

---

Attempt 1 , rightclick and create the type, it produces an system:ArraySegment

<system:ArraySegment x:Key="StandardShadowEffect" x:TypeArguments="Effect">

</system:ArraySegment>

System.ArrayTypeMismatchException: Attempted to access an element as a type incompatible with the array

---

Attempt 2 , List

 <generic:List x:Key="StandardShadowEffect" x:TypeArguments="Effect">

 </generic:List>

System.ArrayTypeMismatchException: Attempted to access an element as a type incompatible with the array

---

Attempt 3 : Array

<x:Array x:Key="StandardShadowEffect" x:TypeArguments="Effect">

</x:Array>

Compile error

Expected Type IList

---

Attempt 4 : Just specifying it and using it

<effects:ShadowEffect x:Key="StandardShadowEffect"
       DistanceX="2"
       DistanceY="2"
       Radius="2"
       Color="{StaticResource HeaderTextShadowColor}" />

Strangely enough this last attempt compiles and doesn't throw, yet no effect is applied

---

Is there anyway to reuse an affect like this, without specifying it on every control? I'm starting to think effects "need" need to be implicitly specified per control

Answer 1

The documentation clearly states that:

An effect instance can only be attached to a single control. Therefore, an effect must be resolved twice to use it on two controls.

So that should expected behaviour. Maybe you can try to extend "needed" UI controls and add a new instance of effect in code behind. Keep in mind that if you do some endless animation in your effect you should remove the effect as well (tricky part).