mbManagerCart Design

This section describes how to access and retrive data from the MBAT cart, the mechanism that allows the sharing of objects among the workspace plugins. The basic interaction between a workspace, derived from mbWorkspaceBase, and the GUI for the cart, JManagerCart, is shown in the figure below. The MBAT cart is an universal object that is shared among all the workspace plugins. The central idea is that any workspace can add an object to the cart and then any another workspace can retrieve this object from the cart.

JManagerCart and mbCartListeners

The JManagerCart communicates with the workspace plugins using the listener methodology that is widely used in Java Swing. The mbCartListener interface defines a single method onEvent( mbCartEvent ):

    public interface mbCartListener extends EventListener {
       public void onEvent( mbCartEvent event );
    }

    public class mbCartEvent extends AWTEvent {
   
        private mbObject m_mbObject;
    
        public final static int ADD = 0;
        public final static int REMOVE = 1;
        public final static int OPEN = 2;
    }

Examples of how to handle different events are given below.

Add/Remove objects to/from the JManagerCart

To add or remove objects, the workspace plugin should add an instance of the JManagerCart to a list of mbCartListeners (the derived workspace must handle storing and managing the cart listeners, ie: private Vector< mbCartListener > / public void addCartListener( mbCartListener )).

On the specific event, the workspace plugin needs to create an instance of mbCartEvent and then fire this event to the mbCartListeners. Upon receiving an mbCartEvent, the JManagerCart handles adding or removing the given mbObject from the mbManagerCart:

    mbCartEvent cartEvent = new mbCartEvent( m_resultTable, mbCartEvent.ADD, annotatedObject );
    for( mbCartListener listener: m_vCartListeners ) 
    {
        listener.onEvent( cartEvent );
    }

Open objects from the JManagerCart

To open an object from the JManagerCart, the workspace plugin must implement the mbCartListener interface and define a onEvent( mbCartEvent ) method to handle the OPEN and REMOVE events that are triggered by the JManagerCart when the user clicks the Open or Remove buttons in the JManagerCart GUI:

    public void onEvent ( mbCartEvent event )
    {
        if( event.getID() == mbCartEvent.OPEN )
        {
            // do something with mbObject
            foo( event.getObject() );
        }
        else( ... )
    }

To register your workspace plugin as a cart listener, you must add your workspace to the JManagerCart cart listeners. Since the JManagerCart is shared among the workspaces, you must be careful to add and remove your workspace cart listener apprioriately. For example, if you add the cart listener only once at startup, then if you switch workspaces, the OPEN event will still be triggered for the hidden workspace since it is still on the mbCartListener list. If you only want the JManagerCart events triggered when the workspace is visible, then as described in the Workspace Plugins section, you can remove and add the cart listeners in the hide() and show() methods:

    public void hide ()
    {
        ...
        // remove cart listener
        JManagerCart.getInstance().removeCartListener( m_viewer );
        ...
    }


    public void show () 
    {
       ...
       // add cart listener
       JManagerCart.getInstance().addCartListener( m_viewer );
       ...
    }