以Button为例：

一般Button有2个状态，按下和正常状态

1.在res下新建drawable文件夹，用以存放自己的Drawable文件

2.在drawable文件夹下新建按下和正常状态shape文件(是图片资源，则略过此步骤)

3.新建Button背景Selector文件

4.为Button的backgroud指定Drawable

代码：

button_noraml.xml

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

    <stroke
        android:width="1dp"
        android:color="#00FF00" />

    <gradient
        android:angle="270"
        android:endColor="#e5e5e5"
        android:startColor="#DCDCDC" />

</shape>

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button_press.xml

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

    <!-- 描边 -->
    <stroke
        android:width="1dp"
        android:color="#00FF00" />
    <!-- 渐变 -->
    <gradient
        android:angle="270"
        android:endColor="#00FF00"
        android:startColor="#90EE90" />

</shape>

————————————————————————————————————————————————————

button_selector.xml

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

    <!-- 按下状态的Drawable -->
    <item android:drawable="@drawable/button_press" android:state_pressed="true"></item>
    <!-- 正常状态的Drawable -->
    <item android:drawable="@drawable/button_noraml"></item>

</selector>

————————————————————————————————————————————————————

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="30dp"
        android:background="@drawable/button_selector"
        android:text="Button" />

</LinearLayout>