public class ExportAsImageAction extends EditorPartAction {
  
  /**
   * Id of this action
   */
  public static final String EXPORT_AS_IMAGE_ID = "export as image";
  
  private static final String DESCRIPTION = "Export as image";
  
  /**
   * Constructor
   * 
   * @param editor
   */
  public ExportAsImageAction(IEditorPart editor) {
    super(editor);
    
    setDescription(DESCRIPTION);
    
    setImageDescriptor(ImageDescriptor.createFromImage(IconProvider.loadImage(IconProvider.EXPORT_ICON)));
    
    setText("Export");
  }
  
  @Override
  protected void init() {
    super.init();
    setId(EXPORT_AS_IMAGE_ID);
  }
  
  @Override
  public void run() {
    ImageSaveUtil.save(getEditorPart());
  }
  
  @Override
  protected boolean calculateEnabled() {
    return getEditorPart() != null;
  }
  
  @Override
  public void setEditorPart(IEditorPart part) {
    super.setEditorPart(part);
  }
}

 private ExportAsImageAction exportAction;
  
  @Override
  protected void buildActions() {
    ...
    exportAction = new ExportAsImageAction(null);
    addAction(exportAction);
  }

  @Override
  public void setActiveEditor(IEditorPart editor) {
    // override this so that the exportAction instance can track the
    // current editor
    super.setActiveEditor(editor);
    exportAction.setEditorPart(editor);
  }

  @Override
  protected void buildActions() {
    ...
    exportAction = new ExportAsImageAction(getPage().getActiveEditor());
    addAction(exportAction);
  }