Java/Android: anonymous local classes vs named classes

Question

I would like to ask what is the good practice on using anonymous classes vs. named inner classes?

I am writing an Android application, which includes many UI elements (buttons, text fields, etc). For many of them I need some kind of listeners, so in onCreate of the application I have bunch of quite small anonymous classes like:

someButton.setOnClickListener(
    new View.OnClickListener() {
        public void onClick(View v) {
            // do something...
        }
    }
);

Each of of such anonymous class is 5 - 20 lines big - small enough and fits good for recommendations from Java™ in a Nutshell book:

In general, you should consider using an anonymous class instead of a local class if:

• The class has a very short body.
• Only one instance of the class is needed.
• The class is used right after it is defined.
• The name of the class does not make your code any easier to understand.

But the problem, IMO, is that onCreate becomes quite big and the code becomes more complex to read and understand by quick looking in to it. It is still easy to understand, but simply too big.

So what would be better practice in such case - have bunch of small inner sub-classes, where each of it is nicely separated , but used just once or better keep using anonymous classes instead?

Answer 1

I don't think there is a clear answer one way or the other. Both styles work fine, its really just what you prefer.

Another option is to have

the contents of each onClick by a single function call, which will keep the anonymous classes very short. I.e:

someButton.setOnClickListener(
    new View.OnClickListener() {
        public void onClick(View v) {
            doSomeButtonClick();
        }
    }
);


private void doSomeButtonClick() {
  // do something
}

Answer 2

Refactor the onCreate() into separate methods grouped by common functionality so you have logical units. If the GUI is complex then it will help you later.

EDIT:

Also, since you are by default indented more by a code formatter when inside an anonymous class your lines need to be shorter to avoid being broken over several lines by the formatter making it longer. This is usually the thing that make it clear that it would be a good time to extract the class and give it a name.