ui_black.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<!--阴影效果-->
    <item
        android:gravity="bottom"
        >
        <shape>

            <size android:height="5dp"/>
            <padding android:bottom="5dp"/>
            <gradient
                android:angle="-90"
                android:endColor="@android:color/transparent"
                android:startColor="#ff000000"/>
        </shape>
    </item>

    <!--底边-->
<item
    android:gravity="bottom">
    <shape android:shape="rectangle">

        <padding android:bottom="1dp"/>
        <size android:height="1dp"/>
        <solid android:color="#bbb"/>
    </shape>
    </item>



</layer-list>