GXT 3:GridSelectionModel SelectionEvent/SelectionChangedEvent未激发

GXT 3问题:

有人知道为什么当我选择网格上的任何一行时,这两个处理程序都不会被触发吗?SelectionModel是GridSelectionModel,设置为单选。

还有什么需要申报的吗?就这么简单,不是吗?我为GXT 2.2添加事件侦听器没有问题,但GXT 3有一些更改。这些事件是用来检测行选择的,不是吗?

SelectionChangedHandler<Summary> gridSelectionChangedHandler = 
  new SelectionChangedHandler<Summary>() {
    public void onSelectionChanged(
      SelectionChangedEvent<Summary> event) {
        Summary rec = event.getSelection().get(0);
        Window.alert("Row = "+ rec.getId());    
    }
  };

SelectionHandler<Summary> gridSelectionHandler =
  new SelectionHandler<Summary>() {
    public void onSelection(SelectionEvent<Summary> event) {
      Summary rec = event.getSelectedItem();
      Window.alert("Row = "+ rec.getId());    
    }
  };

public SummaryViewImpl() {
  uiBinder.createAndBindUi(this);
  this.grid.addSelectionChangedHandler(gridSelectionChangedHandler);
  this.grid.addSelectionHandler(gridSelectionHandler);
}

然而,我对RowClickEvent没有问题,因为以下内容正在启动:

@UiHandler({ "grid" })
void onRowClick(RowClickEvent event){
    int row = event.getRowIndex();
    Window.alert("Row = "+ row);        
}

grid是SummaryGrid的一个实例:

public class SummaryGrid
extends Grid<Summary>{


  {
    this.sm = new GridSelectionModel<Summary>();
    this.sm.setSelectionMode(SelectionMode.SINGLE);
  }


  blah ... blah ...

  public HandlerRegistration addSelectionChangedHandler(SelectionChangedHandler<Summary> handler){
    return this.getSelectionModel().addSelectionChangedHandler(handler);
  }

  public HandlerRegistration addSelectionHandler(SelectionHandler<Summary> handler){
    return this.getSelectionModel().addSelectionHandler(handler);
  }

  blah ... blah ...
}