Use of selector

Example

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_selected="true" android:drawable="@drawable/button_bg_press" /> <item android:state_focused="true" android:drawable="@drawable/button_bg_press" /> <item android:state_pressed="true" android:drawable="@drawable/button_bg_press" /> <item android:drawable="@drawable/button_bg_normol" /> </selector>

transfer:

 <Button
        android:id="@+id/bt_about"
        style="@style/Button_style"
        android:background="@drawable/button_selector" android:layout_width="250dp" android:layout_height="50dp" android:layout_margin="5dp" android:textColor="@color/test_color_selector" android:text="@string/about" />