<?xml version="1.0" encoding="UTF-8"?>

<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <!-- 边框颜色值 -->

    <item>

        <shape>

            <solid android:color="#000000" />

        </shape>

    </item>

   <item android:bottom="1dp"> <!--设置只有底部有边框-->

        <shape>

            <solid android:color="#ffffff" />

        </shape>

    </item>

</layer-list>