JFace Actions¶

The default wizard provided by eclipse will let you add to the top-level toolbar or menu system using the concept of Actions and ActionSets.

Action¶

You can use action directly - this is an acceptable approach if you are going to use the action within your plugin.

newAction = new Action("New...") {
    public void run() {
        registerDatasource();
    }
};
newAction.setImageDescriptor(getImageDescriptor("new.gif"));

Example use with a toolbar:

IToolBarManager mgr = getViewSite().getActionBars().getToolBarManager();
mgr.add( newAction );

ActionSet¶

You can contributing actions via action sets. An action set is a mechanism that allows a plug-in to contribute menus, menu items, and toolbar items to the main menu bar and toolbar of the Workbench window. It is important to understand what action sets are meant to be used for. An action set should contribute common actions which are not specific to any particular view or editor. The class defined in the plugin ActionSets extension point must implement org.eclipse.ui.IWorkbenchWindowActionDelegate interface if the pulldown attribute is false, or org.eclipse.ui.IWorkbenchWindowPulldownDelegate interface if the pulldown attribute is true. This delegate class can control the enabled/disabled state of the action when the selection changes, but only once the plug-in is loaded. Until then, the enabled/disabled state of the action is controlled by other XML attributes like enablesFor and selection.

Workbench and Actions¶

Uses IWorkbenchWindowActionDelegate ...

public class EditStyleAction implements IWorkbenchWindowActionDelegate {

    public final static String ID = "org.locationtech.udig.style.openStyleEditorAction"; //$NON-NLS-1$

    private Layer selectedLayer;

    public void dispose() {
    }

    public void init( IWorkbenchWindow window ) {

    }

    public void run( IAction action ) {
        Display.getDefault().asyncExec(new Runnable(){
            public void run() {
                StyleView styleView = null;
                try {
                    IWorkbenchPage page  = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage();
                    page.showView( StyleView.VIEW_ID );

                    styleView = (StyleView)
                    if (selectedLayer != null);
                        styleView.setSelectedLayer(selectedLayer);
                }
                catch (PartInitException e2) {
                    e2.printStackTrace();
                }
            }
        });
    }

    public void selectionChanged( IAction action, ISelection selection ) {
        if (selection.isEmpty() || !(selection instanceof IStructuredSelection))
            return;

        StructuredSelection sselection = (StructuredSelection)selection;
        if (sselection.getFirstElement() instanceof Layer) {
            selectedLayer = (Layer)sselection.getFirstElement();
        }
    }
}

View and Actions¶

Uses IViewActionDelegate ... The interface IViewActionDelegate allows the action delegate, during initialization, to target itself with the view instance it should work with. The action delegate must implement the method setActiveEditor(IAction action, IEditorPart targetEditor). Action enablement is declared in XML because plug-ins are loaded lazily. Until an action is actually invoked by the user, the plug-in is not loaded and the Workbench uses the enablement logic declared in XML. Once a plug-in is loaded, the delegate class is notified of selection changes and can update the enabled/disabled state of the action. Refer to the org.eclipse.ui.IActionDelegate.selectionChanged(IAction action, ISelection selection) method documentation for more details.

View Context Menu¶

The class defined for the action must implement org.eclipse.ui.IViewActionDelegate interface if contributing to a view’s context menu.

EnablesFor attribute control the enabled/disabled state of the action based on the current selection. Its value is the selection count condition which must be met to enable the action. If not the action is disabled. If attribute is skipped default is enable for any number of items selected.

Formats	Description
!	0 items selected
?	0 or 1 items selected
+	1 or more items selected
multiple, 2+	2 or more items selected
n	a precise number of items selected (e.g. 4)
-	any number of items selected

Here is an example used in udig with the zoom to layer action in the Layers View. Create an object contribution to ILayer class and add the zoom to layer action to your plugin.

<objectContribution
          adaptable="false"
          objectClass="org.locationtech.udig.project.ILayer"
          id="org.locationtech.udig.project.ui.LayerContribution">
   <action
        label="%zoomToLayer.label"
        icon="icons/elcl16/zoom_layer_co.gif"
        tooltip="%zoomToLayer.tooltip"
        class="org.locationtech.udig.project.ui.internal.actions.ZoomToLayer"
        style="push"
        id="org.locationtech.udig.project.ui.zoomTo"/>
</objectContribution>

Then create the ZoomToLayer class that implements IViewActionDelegate

public class ZoomToLayer extends ActionDelegate implements IViewActionDelegate {

    IStructuredSelection selection;

    public void selectionChanged( IAction action, ISelection selection ) {
       try{
          this.selection=(IStructuredSelection) selection;
       }catch (Exception e) {
          //do nothing
       }
    }

    public void runWithEvent( IAction action, Event event ) {
       try {
          PlatformUI.getWorkbench().getActiveWorkbenchWindow().run(false, true,
                 new IRunnableWithProgress() {

                    public void run(IProgressMonitor monitor) {
                       Envelope bounds = new Envelope();
                       bounds.setToNull();
                       Map map=((Layer)selection.getFirstElement()).getContextModel().getMap();
                       for( Iterator iter = (selection).iterator(); iter.hasNext(); ) {
                          Layer layer = (Layer) iter.next();
                          if( layer.getContextModel().getMap()!=map )
                             return;

                          Envelope bbox=null;
                          try {
                             bbox = layer.getBounds(monitor, map.getViewportModel().getCRS());
                          } catch (IOException e) {
                          }

                          if( bbox==null)
                             continue;

                          if( bounds.isNull() )
                             bounds.init(bbox);
                          else
                             bounds.expandToInclude( bbox );

                          if( !bounds.isNull() ) {
                             map.sendCommandASync(
                                 NavigationCommandFactory.getInstance().createSetViewportBBoxCommand(bounds));
                          }
                       }
                   }
               });
        } catch (Exception e) {
            CorePlugin.log(ProjectUIPlugin.getDefault(), e);
        }
    }

Editor and Actions¶

Uses IEditorActionDelegate ... must implement org.eclipse.ui.IEditorActionDelegate interface if contributing to an editor’s context menu. The interface IEditorActionDelegate allows the action delegate to retarget itself to the active editor. The action delegate must implement the method setActiveEditor(IAction action, IEditorPart targetEditor).

public class CommitAction implements IEditorActionDelegate {

    private MapEditor editor;

    public void setActiveEditor( IAction action, IEditorPart targetEditor ) {
        editor=(MapEditor) targetEditor;
    }

    public void run( IAction action ) {
        try {
            editor.getMap().getEditManagerInternal().commitTransaction();
        } catch (IOException e) {
            // Shouldn't happen but...
            ProjectUIPlugin.getDefault().getLog().log(new Status(IStatus.ERROR,
                    "org.locationtech.udig.project",0,"Error commiting transaction",e)); //$NON-NLS-1$ //$NON-NLS-2$
        }
    }
    public void selectionChanged( IAction action, ISelection selection ) {
    }
}

Object and Actions¶

Uses IObjectActionDelegate ... For object contributions, the class attribute of the action element is the name of a Java class that implements the org.eclipse.ui.IObjectActionDelegate interface. The interface IObjectActionDelegate allows the action delegate to retarget itself to the active part. The action delegate must implement the method

setActivePart(IAction action, IWorkbenchPart targetPart)

Q: Where are the Actions?

Proxy Pattern and Actions: In the quest for lazy loading of plug-ins the RCP makes use of the proxy pattern to delay the loading of Actions. For most instances a particular extention point will create a proxy based on configuration information; and it will be this proxy that turns around and creates/calls your class.

uDig