What is the controller in Java Swing?

Question

I would like to apply the MVC design to my Java application using Swing in a meaningful way. Therefore my question is, how the controllers would be structured in Java Swing?

Answer 1

For a clear separation of View and Controller, you could do it like this:

public class MyView extends SomeSwingComponent {

   private Controller controller;
   public View(Controller controller) {
     this.controller = controller;
     JButton saveButton = new JButton("Save");
     button.addActionListner(controller.getSaveButtonListener());
   }
}

---

public class MyController implements Controller {
  private ActionListener saveButtonListener;
  @Override
  public ActionListener getSaveButtonListener() {
    if (saveButtonListener == null) {
      saveButtonListener = new ActionListener() {
        // ...
      }
  }
}

Now we could implement different controllers which could be convenient, if we want to use the view component with different models. The controller is a strategy of the actual view instance.

In most cases it is just enough to define listeners as anonymous classes, because they usually just call a method on the controller instance. I use listeners usually as simple dispatchers - they receive a notification and send a message to another object. A listener class should implement too much business logic, that's beyond its responsibilties.