COMP 3670 - Understanding Objects

Alex Bunardzic, British Columbia Institute Of Technology (BCIT)

Code examples (Week 09), Action Framework:

The Abstractions

In order to illustrate the concepts presented during Lecture #9, we have introduced a Java GUI application. This application is supposed to demonstrate the use of the Action Framework. We've started with a simple interface Resource (this is the simplest possible interface, as it doesn't contain any prescriptions for behavior -- no methods whatsoever):

public interface Resource{
}

Another abstraction we have introduced is the Manager interface:

public interface Manager {
    public void addResource(Resource resource);
    public Iterator iterator();
}

This interface prescribes to behavior methods: how to add the Resource, and how to supply the abstract iterator which will not reveal the underlying implementation of the Resource.

The Implementation

Action Manager is the class that implements the Manager interface:

class ActionManager implements Manager{
    private Vector resources;

    public ActionManager(){
        resources = new Vector();
    }

    public void addResource(Resource resourceIn){
        resources.add(resourceIn);
    }

    public Iterator iterator(){
        return resources.iterator();
    }
}

The resources are managed by putting them inside a very simple collection -- a Vector.

Resources are implemented by extending the GUI framework abstraction -- AbstractAction; for instance, DeleteAction class will implement the customized code that will handle the delete operation in the actionPerformed method:

class DeleteAction extends javax.swing.AbstractAction implements Resource{
    public DeleteAction(String name, Icon icon){
        super(name, icon);
    }

    public void actionPerformed(ActionEvent e){
        // place your custom delete code here...
    }
}

The Application class will instantiate the Manager and will add the appropriate Resources to it; then it will instantiate the GUI and will set the ActionManager for the GUI:

class Application{
    private Manager manager;
    private GUI gui;

    public Application(){
        manager = new ActionManager();
        manager.addResource(new SaveAction("Save", new ImageIcon("save.gif")));
        manager.addResource(new DeleteAction("Delete", new ImageIcon("delete.jpg")));
        manager.addResource(new NewAction("New", new ImageIcon("new.gif")));
        manager.addResource(new CloneAction("Cloning", new ImageIcon("clone.gif")));
        gui = new GUI("Action Framework");
        gui.setActionManager(manager);
    }

    public static void main(String[] args) {
        new Application();
    }
}

Finally, the GUI class will set up the graphical framework, and then interrogate the Manager in order to include all the Resources managed by the Manager:

import java.awt.*;
import javax.swing.*;
import java.util.*;

class GUI extends JFrame {
    private Manager manager;
    private JMenu menu;
    private JToolBar toolbar;
    private Action action;

    public GUI(){
        setUp();
    }

    public GUI(String title){
        super(title);
        setUp();
    }

    public void setActionManager(Manager manager){
        Iterator iterator = manager.iterator();
        while(iterator.hasNext()){
            action = (Action)iterator.next();
            menu.add(action);
            toolbar.add(action);
        }
    }

    private void setUp(){
        getContentPane().setLayout(new BorderLayout());
        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);
        menu = new JMenu("File");
        menuBar.add(menu);
        toolbar = new JToolBar();
        getContentPane().add(toolbar, "North");
        setBounds(20, 40, 350, 150);
        setVisible(true);
    }
}

It is important to note that in the above framework, we cannot find any place where the decisions as to which Action to run are being made. Nowhere can we find and if-then-else constructs. The decision is actualy made by the framework.

Click here to download the icons for this application