Is it possible to use AppThemeBinding in Android Custom Styles?

Question

I'm trying to implement Darkmode for Android by using the new AppThemeBinding. It works fine for Android and iOS but i do not have a clue on how to implement it for custom renderers or custom styles.

For example i got a custom Stepper renderer which looks something like this:

protected override void OnElementChanged(ElementChangedEventArgs<Stepper> e)
{
    base.OnElementChanged(e);
    if (Control != null)
    {
        Android.Widget.Button buttonDown = (Android.Widget.Button)Control.GetChildAt(0);
        Android.Widget.Button buttonUp = (Android.Widget.Button)Control.GetChildAt(1);
        if(e.NewElement != null)
        {
            //Button Down
            buttonDown.SetBackgroundResource(Resource.Drawable.button_bg_left);
            buttonDown.LayoutParameters = new LinearLayout.LayoutParams(DpToPixel(50), DpToPixel(33));
            buttonDown.SetPadding(0,0,0,0);
            buttonDown.SetTextColor(Android.Graphics.Color.ParseColor("#007bff"));
            //Button Up
            buttonUp.SetBackgroundResource(Resource.Drawable.button_bg_right);
            buttonUp.LayoutParameters = new LinearLayout.LayoutParams(DpToPixel(50), DpToPixel(33));
            buttonUp.SetPadding(0, 0, 0, 0);
            buttonUp.SetTextColor(Android.Graphics.Color.ParseColor("#007bff"));
                  
        }
    }
}

I'm setting a background resource which is a .xml file and looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="#FFFFFF"/>
    <stroke android:width="1dp" android:color="#007bff" />
    <corners
            android:topLeftRadius="5dp"
            android:bottomLeftRadius="5dp"/>
</shape>

Since the AppThemeBinding is a Markup Extension and works inside .xaml files, i have no clue how i could implement color changes for my android specific renderers?

How could i go about changing the color of my custom shape for Light/Darkmode?

Answer 1

You can Detect the current system theme in the renderer and then set the corresponding color:

class MyStepperRenderer : StepperRenderer
{
    public MyStepperRenderer(Context context) : base(context)
    {
    }

    protected override void OnElementChanged(ElementChangedEventArgs<Stepper> e)
    {
        base.OnElementChanged(e);

        OSAppTheme currentTheme = Xamarin.Forms.Application.Current.RequestedTheme;

        if (currentTheme == OSAppTheme.Light)
        {
            //
        }
        else
        {
            //
        }
    }
}