java - GWT:如何使用 AsyncDataModel 填充 CellTree 的初始列表？

Question

我正在使用 GWT 2.4。我想创建一棵具有一组固定顶级节点的树，但在打开每个节点时，会从服务器动态检索数据。我找到了 AsyncDataProvider 类来帮助我，但我无法弄清楚如何使用一组初始值预先填充数据模型。我有这个代码(不工作)...

public class CellTreeExample implements EntryPoint {

  /**
   * The model that defines the nodes in the tree.
   */
  private static class CustomTreeModel implements TreeViewModel {

    /**
     * Get the {@link NodeInfo} that provides the children of the specified
     * value.
     */
    public <T> NodeInfo<?> getNodeInfo(T value) {
      /*
       * Create some data in a data provider. Use the parent value as a prefix
       * for the next level.
       */
      AsyncDataProvider<String> dataProvider = new AsyncDataProvider<String>() { 
          @Override
          protected void onRangeChanged(HasData<String> display) {
            // Execute dynamic logic here.
      }
      };

      // Set a default set of nodes.
      TextCell textCell = new TextCell();
      final CellList<String> cellList = new CellList<String>(textCell);
      final List<String> rootNodes = getRootNodes();
      cellList.setRowCount(rootNodes.size(), true);
      dataProvider.addDataDisplay(cellList);

      // Return a node info that pairs the data with a cell.
      return new DefaultNodeInfo<String>(dataProvider, new TextCell());
    }

    public boolean isLeaf(Object value) {
        // some logic
    }
  }

  public void onModuleLoad() {
    // Create a model for the tree.
    TreeViewModel model = new CustomTreeModel();

    /*
     * Create the tree using the model. We specify the default value of the
     * hidden root node as "Item 1".
     */
    CellTree tree = new CellTree(model, "Item 1");

    // Add the tree to the root layout panel.
    RootLayoutPanel.get().add(tree);
  }

当我启动应用程序时，什么也没有出现，并且我已确认初始单元格列表包含 6 个项目。有什么想法为什么他们不显示吗？构建用于 CellTree 的 CellList 时，TextCell 不是正确的类型吗？ - 戴夫

Answer 1

// summarizing pseudocode
public <T> NodeInfo<?> getNodeInfo(final T value) {
  if(value == null) {  // root, return static list of top level nodes
    return new DefaultNodeInfo<String<( 
        new ListDataProvider<String>(Arrays.<String>asList("node1", "node2" ... ));
        , new TextCell());
  }
  else {
    AsyncDataProvider<String> dataProvider = new AsyncDataProvider<String>() { 
      @Override
      protected void onRangeChanged(HasData<String> display) {
        // Execute dynamic logic here - and fetch data from server or wherever
        // call updateRowData() in when data is available
        updateRowData(display.getVisibleRange(), /* List<String> results */);
      }
    }  

    return new DefaultNodeInfo<String>(dataProvider, new TextCell());
  }
}