Using UDIGApplication¶

The base class UDIGApplication serves three purposes:

It is a show case of what the SDK can do; usable by end-users as a functional GIS Application
It is an example for other RCP developers to copy (either cut and paste or subclass)
It provides static final helper methods that can be used by other RCP developers

This class is to be used as part of a product definition:

UDIG 1.0: IPlatformRunnable interface provided by RCP
UDIG 1.1: IApplication interface provided by Equinox

Links to Related Content:

For the latest instructions please see the Getting Started tutorial

As a Showcase¶

As a showcase the UDIGApplication needs to provide a fine balance between enough functionality to be useful; and not so much that the result is intimidating.

The actual uDig application does not do much:

Kicks the org.locationtech.udig.libs “Activator” into loading the EPSG database
Does a few sanity checks about the execution environment; displaying warning dialogs if everything is not right
Starts up a workbench using the UDIGWorkbenchAdvisor

As a Base¶

As base class UDIGApplication must ensure that every contribution shows up in a logical part of the user interface. This is especially important with respect to menubars and toolbars; we must include examples of each kind of contribution.

Check for JAI

This has moved to an org.eclipse.ui.startup for the org.locationtech.udig.ui. It will display a dialog if JAI is not found.

Login

Setting up an UDIGApplication that requires a login is a common request. This example shows how to use the checkLogin() method to talk to a “Client” plug-in and call its login method.

The “Client’ plug-in technique is used when you have a Client plugin that holds on to a Spring remoting Session with a J2EE server application.

Here is an example of overriding the UDIGApplication checkLogin() method.

public boolean checkLogin() {
        LoginDialog loginDialog = new LoginDialog(
                "Connecting Communities Login",
                "Please login to Connecting Communities:" );

        boolean login= false;
        while( !login ){
            int result = loginDialog.open();
            if( result == MessageDialog.OK){
                try {
                    login = Client.getDefault().login( loginDialog.getUser(), loginDialog.getPassword() );
                    if( !login ){
                        loginDialog.setMessage("Could not login - please try again");
                    }
                } catch (Exception connectionProblem) {
                    MessageDialog.openInformation(null, "Could not Connect", connectionProblem.toString() );

                    return false; // probably should prompt user here?
                }
            }
            else {
                return false; // user cancelled
            }
        }
        return true;
    }

The above example made use of a really simple MessageDialog shown bellow:

public class LoginDialog extends MessageDialog {
    String user;
    String password;
    public LoginDialog( String title, String dialogMessage) {
        super(null, title, null, dialogMessage, QUESTION,
                new String[]{"Login","Exit"}, 0 );
    }

    protected Control createCustomArea(Composite parent) {
        Composite composite = new Composite(parent, SWT.NONE);
        composite.setLayout( new GridLayout(2,false) );

        Label label = new Label( composite, SWT.RIGHT );
        label.setText("User:");
        GridData gridData = new GridData( SWT.FILL, SWT.FILL, false, false );
        gridData.widthHint = 100; // just a suggestion
        label.setLayoutData( gridData );

        final Text userText = new Text( composite, SWT.SINGLE );
        userText.setLayoutData( new GridData( SWT.FILL, SWT.CENTER, true, false ));
        userText.addModifyListener( new ModifyListener(){
            public void modifyText( ModifyEvent e ) {
                user = userText.getText();
            }
        });

        label = new Label( composite, SWT.RIGHT );
        label.setText("Password:");
        label.setLayoutData( gridData );

        final Text passwordText = new Text ( composite, SWT.SINGLE | SWT.PASSWORD );
        passwordText.setLayoutData( new GridData( SWT.FILL, SWT.CENTER, true, false ));
        passwordText.addModifyListener( new ModifyListener(){
            public void modifyText( ModifyEvent e ) {
                user = passwordText.getText();
            }
        });
        return null;
    }

    public String getUser() {
        return user;
    }
    public String getPassword() {
        return password;
    }
    public void setMessage( String message ){
        messageLabel.setText( message );
    }
}

Init

The init method as provided will kick the org.locationtech.udig.libs Activator class into loading the EPSG database. It actually does a quick sanity check first (to see if loading will take a long time).

/**
  * We have a couple things that need to happen
  * before the workbench is opened. The org.eclipse.ui.startup
  * extension point is willing to run stuff for us *after*
  * the workbench is opened - but that is not so useful
  * when we need to configure the EPSG database for libs
  * and load up the local catalog.
  * <p>
  * Long term we will want to create a startup list
  * (much like we have shutdown hooks).
  */
 protected boolean init() {
     ProgressMonitorDialog progress = new ProgressMonitorDialog( Display.getCurrent().getActiveShell());
     final Bundle bundle = Platform.getBundle(Activator.ID);

     // We should kick the libs plugin to load the EPSG database now
     if( ThreadedH2EpsgFactory.isUnpacked()){
         // if there is not going to be a long delay
         // don't annoy users with a dialog
         Activator.initializeReferencingModule( null );
     }
     else {
         // We are going to take a couple of minutes to set this up
         // so we better set up a progress dialog thing
         //
         try {
             progress.run(false,false, new IRunnableWithProgress(){
                 public void run( IProgressMonitor monitor ) throws InvocationTargetException,
                         InterruptedException {
                     Activator.initializeReferencingModule( monitor);
                 }
             });
         } catch (InvocationTargetException e) {
             Platform.getLog(bundle).log(
                     new Status(IStatus.ERROR, Activator.ID, e.getCause().getLocalizedMessage(), e
                             .getCause()));
             return false;
         } catch (InterruptedException e) {
             Platform.getLog(bundle).log(
                     new Status(IStatus.ERROR, Activator.ID, e.getCause().getLocalizedMessage(), e
                             .getCause()));
             return false;
         }
     }
     // We should kick the CatalogPlugin to load now...
     return true;
 }

As a Utility Class¶

Utility methods exist to perform checks commonly needed at startup.

Java Advanced Imaging

The checkForJAI method will return false if JAI is not installed into the current JRE:

boolean optional = UDIGApplication.checkForJAI();

Your application may need JAI or may not; it is required for raster operations - if your application is limited to vector work you can get by without this functionality.

GDI

The checkForGDI method will return false if GDI+ is required (ie on WIN_32 platform) and not available:

boolean required = UDIGApplication.checkForGDI();

We required GDI+ for SWT matrix calculations; instructions on how to obtain GDI+ for older versions are provided as part of the running udig instructions.