How to access a list of resources via data binding

Let’s imagine you need to provide a gradient background consisting of arbitrarily many colors to a View.

This can’t be done via regular drawable XML as a gradient within a shape can only define three colors: startColor, centerColor, endColor.

To reach our goal we will be using data binding.

We define an integer array in e.g. arrays.xml and fill it with the desired color resources:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <integer-array name="some_colors">
        <item>@color/color0</item>
        <item>@color/color1</item>
        <item>@color/color2</item>
        <item>@color/color3</item>
        <item>@color/color4</item>
    </integer-array>
</resources>

Then we define a binding adapter to apply the colors in a gradient to the background of the View:

object ViewBindingAdapters {

    @JvmStatic
    @BindingAdapter("background_gradient_colors")
    fun setBackgroundColors(view: View, colors: IntArray) {
        view.background = GradientDrawable(
                GradientDrawable.Orientation.LEFT_RIGHT,
                colors
        )
    }
}

Now we can define the background colors in our layout XML (apply it to any View class you like):

object ViewBindingAdapters {

    @JvmStatic
    @BindingAdapter("background_gradient_colors")
    fun setBackgroundColors(view: View, colors: IntArray) {
        view.background = GradientDrawable(
                GradientDrawable.Orientation.LEFT_RIGHT,
                colors
        )
    }
}

Note, that we have to reference integer-array resources with @intArray in data binding expressions!