code: protected void onTimeKeyPressed(KeyUpEvent event) {
  
          switch (event.getNativeEvent().getKeyCode()) {
              case KeyCodes.KEY_CTRL:
              case KeyCodes.KEY_SHIFT:
              case KeyCodes.KEY_ALT:
              case KeyCodes.KEY_LEFT:
              case KeyCodes.KEY_RIGHT:
                  break;
              case KeyCodes.KEY_ENTER:
                  updateFromPicker();
                  hidePopup();
                  break;
              default:
                  Scheduler.get().scheduleDeferred(new ScheduledCommand() {
  
                      public void execute() {
  
                          executeTimeAction();
                          fireChange(getValue(), false);
                      }
                  });
                  break;
          }
      }
docs: If the user presses enter in the time field the value of the
  picker should be updated and the the popup should be closed.<p>
  
  In any other case the popup should be prevented to being closed.<p>
  
  @param event the key pressed event