<?xml version="1.0" encoding="utf-8"?><!-- 默认按钮样式 -->
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <!-- 按压状态 -->
    <item android:state_pressed="true">
        <shape android:shape="rectangle">
            <solid android:color="#ff51a9e5" />
        </shape>
    </item>

    <!-- 焦点状态 -->
    <item android:state_focused="true">
        <shape android:shape="rectangle">
            <solid android:color="#ff51a9e5" />
        </shape>
    </item>

    <!-- 默认状态 -->
    <item>
        <shape android:shape="rectangle">
            <solid android:color="@color/transparent" />
        </shape>
    </item>

</selector>