Good example, you might want to override the trackwheelListener. As well, you don't need to enter the entire class path for the class.
public class MyTextInput2 extends UiApplication implements FieldChangeListener
would be sufficient.
What I like to do is override the FieldChangeListener on each button individually like this...
ButtonField testButton = new ButtonField("Click Me");
public void fieldChanged(Field field, int context)
It helps me keep the code for the event close to the button object.