The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
<?xml version="1.0" encoding="utf-8"?>
<shape
xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<stroke
android:width="2dp"
android:color="@color/layout_border_color" />
<padding
android:left="10dp"
android:top="5dp"
android:right="10dp"
android:bottom="2dp" />
<corners
android:radius="2dp" />
</shape>