Use the <shape>
tag to create a drawable in XML with rounded corners. (You can do other stuff with the shape tag like define a color gradient as well).
Here’s a copy of a XML file I’m using in one of my apps to create a drawable with a white background, black border and rounded corners:
<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<solid android:color="#ffffffff"/>
<stroke android:width="3dp"
android:color="#ff000000" />
<padding android:left="1dp"
android:top="1dp"
android:right="1dp"
android:bottom="1dp" />
<corners android:radius="7dp" />
</shape>