Bean Item容器Vaadin：重新排序

Question

我试图使导出的BeanItemContainer的排序与Vaadin Grid中可见的列相同。我已经花了两天时间试图找到一种方法来做到这一点。但是，我无法找到任何解决方案。

这是我的代码：

public class TestView extends VerticalLayout implements View{
public static final String VIEW_NAME = "test";

private Grid grid = new Grid();
private BeanItemContainer<PeddlingBeanNestle> bean = new BeanItemContainer<PeddlingBeanNestle>(PeddlingBeanNestle.class);
private ExcelExporter exporter = new ExcelExporter();

@Override
public void enter(ViewChangeEvent event) {
    setup();
}

private void setup(){
    grid.setColumnReorderingAllowed(true);
    grid.setContainerDataSource(bean);
    exporter.setContainerToBeExported(bean);
    exporter.setCaption("Export");
    java.util.List<Grid.Column> a = grid.getColumns();

    for (Grid.Column b : a){
        b.setHidable(true);
    }

    grid.addColumnVisibilityChangeListener(new Grid.ColumnVisibilityChangeListener() {
        @Override
        public void columnVisibilityChanged(Grid.ColumnVisibilityChangeEvent event) {

            if(event.isHidden()){
                Notification.show(event.getColumn().getPropertyId().toString() +" hidden");
                System.out.println(event.getColumn().getPropertyId());
                bean.removeContainerProperty(event.getColumn().getPropertyId());
            } else {
                Notification.show(event.getColumn().getPropertyId().toString() +" displayed");
                bean.addContainerProperty(event.getColumn().getPropertyId(), PeddlingBeanNestle.class, "");
            }
        }

    });

    grid.addColumnReorderListener(new Grid.ColumnReorderListener() {
        @Override
        public void columnReorder(Grid.ColumnReorderEvent event) {
            Notification.show(grid.getColumns().toString());
        }
    });

    addComponent(grid);
    addComponent(exporter);
}}

在添加容器时，我收到Null Pointer Exception。我不知道如何将已删除的属性放回去。

我只是希望能够以与Grid中显示的顺序相同的方式导出Vaadin Grid中的数据。

非常感谢任何帮助。干杯！