You will always want a pressed state for your buttons, so state list drawables are a critical component of any Android app. But what about shape drawables and layer list drawables? Should you use them?

XML drawables are flexible. You can use them for many purposes, and you can easily update them in the future. With a combination of layer list drawables and shape drawables, you can create complex backgrounds without using an image editor. If you decide to change the color scheme in BeatBox, updating the colors in an XML drawable is easy.

In this chapter, you defined your XML drawables in the drawable directory with no resource qualifiers for the screen density. This is because XML drawables are density independent. With a standard background that is an image, you will typically create multiple versions of that same image in different densities so that the image will look crisp on most devices. XML drawables only need to be defined once and will look crisp at any screen density.