Implementation

For information about the design and functionality of the MIDlet, see section Design.

To implement the ListDemoModule class:

1. Create the ListDemoModule.java class file.

2. Import the required classes.

   import org.eclipse.ercp.swt.mobile.Command;
   import org.eclipse.ercp.swt.mobile.QueryDialog;
   import org.eclipse.ercp.swt.mobile.TimedMessageBox;
   import org.eclipse.swt.SWT;
   import org.eclipse.swt.events.SelectionEvent;
   import org.eclipse.swt.events.SelectionListener;
   import org.eclipse.swt.layout.FillLayout;
   import org.eclipse.swt.widgets.Composite;
   import org.eclipse.swt.widgets.List;
   import org.eclipse.swt.widgets.Shell;

3. Set ListDemoModule to implement DemoModule and SelectionListener. MIDlets use the SelectionListener interface to receive events when a selection occurs in a Control.

   public class ListDemoModule implements DemoModule, SelectionListener
   {

4. Create the required variables and the ListDemoModule class constructor.

       private Shell demoShell;
       private Shell parent;
       private Composite demoComposite;
       private List demoList;
   
       private Command backCommand;
       private Command addCommand;
       private Command removeCommand;
   
       private static final String[] originalContent = new String[] { "Apples", "Oranges", "Grapefruit", "Milk" };
   
       public ListDemoModule()
       {
       }

5. The DemoModule interface requires the class to implement three methods:

   • getDescription returns a simple description of the module.

         public String getDescription()
         {
             return "Demonstrates the List component";
         }

   • getTitle returns the title of the module.

         public String getTitle()
         {
             return "Shopping List";
         }

   • runDemo runs the demonstration of the module. For the ListDemoModule, the method sets up the demonstration and the selection listeners.

         public void runDemo(Shell parent)
         {
             this.parent = parent;
             demoShell = new Shell(SWT.MAX);
             demoShell.setLayout(new FillLayout(SWT.VERTICAL));
             demoShell.setText("Shopping List");
     
             demoComposite = new Composite(demoShell, SWT.NONE);
             demoComposite.setLayout(new FillLayout(SWT.VERTICAL));
             demoShell.layout();
     
             backCommand = new Command(demoShell, Command.EXIT, 0);
             backCommand.setText("Back");
             backCommand.addSelectionListener(this);
     
             addCommand = new Command(demoShell, Command.SELECT, 1);
             addCommand.setText("Add");
             addCommand.addSelectionListener(this);
     
             removeCommand = new Command(demoShell, Command.SELECT, 1);
             removeCommand.setText("Remove");
             removeCommand.addSelectionListener(this);
     
             //first we create a multiple selection list
             demoList = new List(demoComposite, SWT.MULTI);
             demoList.addSelectionListener(this);
             //then we set the original content
             demoList.setItems(originalContent);
     
             demoComposite.layout();
             demoShell.open();
             demoShell.setActive();
         }

6. The element module classes can use some helper methods. The ListDemoModule class uses the following helper methods:

   • widgetSelected and widgetDefaultSelected handle selections in the Control. The user can add and remove list items, and exit the list.

         public void widgetSelected(SelectionEvent e)
         {
             if(e.widget.equals(backCommand))
             {
                 back();
             }
             else if(e.widget.equals(addCommand))
             {
                 add();
             }
             else if(e.widget.equals(removeCommand))
             {
                 remove();
             }
         }
     
         public void widgetDefaultSelected(SelectionEvent e)
         {
         }

   • back closes the list view and returns to the previous view in the MIDlet.

         private void back()
         {
             demoShell.dispose();
             demoShell = null;
             parent.getShell().setActive();
         }

   • add is used to add a new item to the list.

         private void add()
         {
             //here we first create a dialog to ask the user for a new item
             QueryDialog dialog = new QueryDialog(demoShell, QueryDialog.STANDARD);
             dialog.setPromptText("I should also remember:", "");
             String itemToAdd = dialog.open();
     
             //check whether the user pressed the cancel button or is trying to add
             //a duplicate item
             if(itemToAdd == null)
             {
                 return;
             }
             else if(demoList.indexOf(itemToAdd) != -1)
             {
                 showMessage("One entry of " + itemToAdd +
                             " should be enough for you to remember...");
                 return;
             }
     
             //add the item to the list
             demoList.add(itemToAdd);
         }

   • remove is used to remove an existing item from the list.

         private void remove()
         {
             //if the user hasn't selected anything
             if(demoList.getSelectionCount() == 0)
             {
                 showMessage("Please mark the items you want to remove first!");
                 return;
             }
     
             //remove the selections from the list
             demoList.remove(demoList.getSelectionIndices());
         }

   • showMessage is used to display messages from the add and remove helper methods.

         private void showMessage(String message)
         {
             TimedMessageBox box = new TimedMessageBox(demoShell, SWT.ICON_ERROR);
             box.setMessage(message);
             box.open();
         }
     }