it's easy to do via XML. Use the following settings:
android:singleLine="true"
android:ellipsize="marquee"
android:marqueeRepeatLimit="marquee_forever"
android:focusable="false"
android:scrollHorizontally="true"
If your TextView is within a RelativeLayout, the width or height will have to be static (i.e. 32dp). If you need dynamic, place the TextView in another View within the RelativeLayout.
In onCreate(), you need to make the TextView selected:
myTextView.setSelected(true);