Using graphics to show button state

We've talked about the versatility of Android Views and how behavior and visual appearance can be customized. In this recipe, we will create a drawable state selector, which is a resource defined in XML that specifies the drawable to use based on the View's state. The most commonly used states, along with the possible values, include:

• state_pressed=["true" | "false"]

• state_focused=["true" | "false"]

• state_selected=["true" | "false"]

• state_checked=["true" | "false"]

• state_enabled=["true" | "false"]

To define a state selector, create an XML file with the <selector> element, as shown:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
</selector>

Within the <selector> element, we define an <item> to identify the drawable to be used based on the specified state(s). Here's an example <item> element using multiple states:

<item
    android:drawable="@android...