如果在Part中注入ICommandService，工具栏处理的项目图标将消失

Question

我在Part的工具栏中添加了一个工具栏处理项。零件堆栈的一部分包含类DataBaseConnectPart。当我注入commandService和IHandlerService时。零件工具栏中的按钮消失。我完全混淆了如何在选择树项时触发命令。

public class DatabaseExplorerPart {
@Inject
private IEventBroker eventBroker;

@Inject
private EPartService partService;

@Inject private ICommandService commandService;
@Inject private IHandlerService service;
@Inject private IEvaluationService evaluationService;

@PostConstruct
public void createControls(Composite parent, EMenuService menuService,  EclipseContext context ) {
    createImages();
    viewer = new TreeViewer(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
    viewer.setContentProvider(new ViewContentProvider());
    viewer.addSelectionChangedListener(new ISelectionChangedListener() {
        @Override
        public void selectionChanged(SelectionChangedEvent arg0) {
            TreeSelection ts = (TreeSelection)arg0.getSelection();
            Object o = ts.getFirstElement();
             if (o instanceof Query){
                    context.set(Constants.KEY_SELECTED_OBJECT_TYPE, "query");
                    context.set(Constants.KEY_SELECTED_OBJECT, o);
                    String name = ((Query)o).getName();
                    if(name.equalsIgnoreCase("New Query")){
                      executeCommand();
                      }
                }
            }
        }
    });
    viewer.setLabelProvider(new ViewLabelProvider());
}
 private void executeCommand(){
 try {
  Command theCommand = commandService.getCommand("com.db.connect.command");
  theCommand.executeWithChecks(new ExecutionEvent(theCommand, new HashMap(), null, evaluationService.getCurrentState()));
  } catch (Exception exception) {
    logger.error(exception.getMessage(), exception);
  }
 }