Anonymous classes
In the last chapter, we briefly introduced anonymous classes. Here, we will learn a little more about them and see how they can help us. When a RadioButton is part of a RadioGroup, the visual appearance of them all is coordinated for us. All we need to do is react when any given RadioButton is pressed. Of course, as with any other button, we need to know when they have been clicked.
A RadioButton behaves differently to a regular Button, and simply listening for clicks in onClick (after implementing OnClickListener) will not work because RadioButton is not designed that way.
What we need to do is use another Java feature. We need to implement a class, an anonymous class, for the sole purpose of listening for clicks on the RadioGroup. The following block of code assumes that we have a reference to a RadioGroup called radioGroup. Here is the code:
radioGroup.setOnCheckedChangeListener(
new RadioGroup.OnCheckedChangeListener() {
@Override
public void...
