Android开发手册Button实现selector选择器

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:Android="Http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <!-- 圆角 -->
    <corners android:radius="5dp" />
    <!--填充颜色-->
    <solid android:color="#00ff00" />
</shape>

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <!--圆角-->
    <corners android:radius="5dp" />
    <!--填充颜色-->
    <solid android:color="#0000ff" />
</shape>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/btn_selector_shape1" android:state_pressed="true" />
    <item android:drawable="@drawable/btn_selector_shape2" android:state_window_focused="false" />
</selector>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white"
    tools:context=".TextActivity">
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="160dp"
        android:background="@drawable/btn_selector0"
        android:text="按下变色"
        android:textColor="@color/white" />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <!--这是第一种方式，利用drwable引用文件-->
    <!--<item android:drawable="@drawable/btn_selector_shape1" android:state_pressed="true" />-->
    <!--<item android:drawable="@drawable/btn_selector_shape2" android:state_pressed="false" />-->
    <!--第二种方式如下-->
    <item android:state_pressed="false">
        <shape android:shape="rectangle">
            <!-- 圆角 -->
            <corners android:radius="5dp" />
            <!--填充颜色为白色-->
            <solid android:color="#0000ff" />
        </shape>
    </item>
    <!--单击时是一个带圆角,白色背景,绿色边框的矩形-->
    <item android:state_pressed="true">
        <shape android:shape="rectangle">
            <!--圆角-->
            <corners android:radius="5dp" />
            <!--填充颜色为白色-->
            <solid android:color="#00ff00" />
        </shape>
    </item>
</selector>