Without Using ANY Drop down Using your Drop Down ICON
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<layer-list>
<item>
<shape>
<gradient android:angle="90" android:endColor="#ffffff" android:startColor="#ffffff" android:type="linear" /><!--For gradient background-->
<stroke android:width="1dp" android:color="#FFF" /><!--For Border background-->
<corners android:radius="0dp" /><!--For background corner-->
<padding android:bottom="3dp" android:left="3dp" android:right="6dp" android:top="3dp" /><!--For padding for all sides-->
</shape>
</item>
<item>
<bitmap android:gravity="center|right" android:src="@drawable/ic_down_arrow" /> // Replace with your Icon
</item>
</layer-list>
</item>