JavaFX の TreeView の展開のパフォーマンス問題のワークアラウンド

public final class TreeViewPerformanceTest extends Application{


  private static boolean USE_WORKAROUND = false;
  private static final int TREE_DATA_SIZE = 1000*100;

  private StringProperty reportProperty;
  private TreeView<String> treeView;

  @Override
  public void start(Stage primaryStage) throws Exception {
    final TextArea report = new TextArea();
    this.reportProperty = report.textProperty();
    buildTreeView();
    BorderPane borderPane = new BorderPane();
    borderPane.setCenter(new StackPane(treeView));
    borderPane.setBottom(report);

    final Scene scene = new Scene(borderPane, 800, 800);
    primaryStage.setScene(scene);
    primaryStage.sizeToScene();
    primaryStage.show();
  }

  private void buildTreeView() {
    this.treeView = new TreeView<String>();
    treeView.setFixedCellSize(25);
    final LazyLoadTreeItem treeItem = new LazyLoadTreeItem("Node");
    treeItem.setExpanded(true);
    treeView.setRoot(treeItem);
    treeView.setEditable(false);

    if(USE_WORKAROUND) {
      treeView.expandedItemCountProperty().addListener((ob,oldValue,newValue)->{
        int scrollToIndex = treeView.getSelectionModel().getSelectedIndex();
        treeView.scrollTo(scrollToIndex);
      });
    }
  }

  private class LazyLoadTreeItem extends TreeItem<String>{
    LazyLoadTreeItem(String title){
      super(title);
    }
    @Override
    public ObservableList getChildren() {
      if(this.loaded) {
        return super.getChildren();
      }
      long t = System.currentTimeMillis();
      this.loaded = true;
      final String value = getValue();

      final LazyLoadTreeItem[] d1a = new LazyLoadTreeItem[TREE_DATA_SIZE];
      for(int i=0; i<d1a.length; i++) {
        d1a[i] = new LazyLoadTreeItem(value + '-' + String.valueOf(i));
      }
      final ObservableList<TreeItem<String>> children = super.getChildren();
      TreeItem<String> selectedTreeItem = treeView.getSelectionModel().getSelectedItem();

      if(USE_WORKAROUND) {
        try {
          treeView.getSelectionModel().clearSelection();
          children.setAll(d1a);
          treeView.getSelectionModel().select(selectedTreeItem);
          int scrollToIndex = treeView.getRow(selectedTreeItem);
          treeView.scrollTo(scrollToIndex);
          treeView.refresh();
// Platform.runLater(()->{
// int scrollToIndex = treeView.getRow(selectedTreeItem);
// treeView.scrollTo(scrollToIndex);
// });

        }catch (Exception e) {
          e.printStackTrace();
        }
      }else {
        children.setAll(d1a);
      }

      String result = value + ": time: " + (System.currentTimeMillis() - t);
      reportProperty.set( reportProperty.get() + "\n" + result );
      return children;
    }

    @Override
    public boolean isLeaf() {
      return false;
    }

    boolean loaded;
  }

  public static void main(String[] args) {
    Application.launch(args);
  }
}