Android Application Development Cookbook - Second Edition

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> ...