自定义按钮三态

使按钮的点击，鼠标移入，鼠标移出，都有不同的图片显示

方法是android:background属性值指定为selector布局文件，布局文件中指定三态图片

1.android:background的selector布局文件：button_selector.xml

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

2.在按钮属性中指定android:background为该selector布局文件

<Button
style="@style/button__next_view_style"
android:background="@drawable/button_selector"
android:text="下一步"
/>