TreeView with mixed cell types

Question

I would like to create a TreeView where some cells are CheckBoxTreeCells and
some aren't. My application domain is a medical search engine where we'd like
to have researcher query a dataset by selecting one or more values. Here's a
simple example:
public class CheckBoxTreeSample extends Application {
    public static void main(String[] args) {
        launch(args);
    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("CheckBoxTree Attempt");
        TreeItem<String> rootItem = new TreeItem<>("Dataset root");
        rootItem.setExpanded(true);
        final TreeView tree = new TreeView(rootItem);
        final TreeItem<String> testResultsItem = new TreeItem<>("Test Results");
        rootItem.getChildren().add(testResultsItem);
        testResultsItem.setExpanded(true);
        final CheckBoxTreeItem<String> normalTreeItem = new CheckBoxTreeItem<>("Normal");
        testResultsItem.getChildren().add(normalTreeItem);
        final CheckBoxTreeItem<String> abnormalTreeItem = new CheckBoxTreeItem<>("Abnormal");
        testResultsItem.getChildren().add(abnormalTreeItem);
        final CheckBoxTreeItem<String> preTreeItem = new CheckBoxTreeItem<>("PreCancer");
        testResultsItem.getChildren().add(preTreeItem);
        final CheckBoxTreeItem<String> cancerTreeItem = new CheckBoxTreeItem<>("Cancer");
        testResultsItem.getChildren().add(cancerTreeItem);
        tree.setCellFactory(CheckBoxTreeCell.<String>forTreeView());
        tree.setRoot(rootItem);
        tree.setShowRoot(true);
        StackPane root = new StackPane();
        root.getChildren().add(tree);
        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.show();
}So I'd like to have the testResultsItem and the rootItem NOT have checkboxes (which is why they are TreeItems), but have the leaf nodes be independent
CheckBoxTreeItems. I tried this alternate factory, but that only seems to control the Boolean Property:
        tree.setCellFactory(CheckBoxTreeCell.<String>forTreeView(new Callback<TreeItem<String>, ObservableValue<Boolean>>() {
          @Override
          public ObservableValue<Boolean> call (TreeItem<String> item) {
            if (item instanceof CheckBoxTreeItem) {
              return new ReadOnlyBooleanWrapper(Boolean.TRUE);
            } else {
              return null; //Don't display an CheckBox - obviously doesn't work...
        }));I recently saw this posting by Jonathan Giles:
http://fxexperience.com/2012/05/listview-custom-cell-factories-and-context-menus/
but I'm not sure how that might apply to this case.
Any help in determining how to remove, or at least disable, non-leaf node checkboxes would be greatly
appreciated!

Answer 1

Something like this:
public class CheckBoxTreeSample extends Application {
  public static void main(String[] args) {
    launch(args);
  @Override
  public void start(Stage primaryStage) {
    primaryStage.setTitle("CheckBoxTree Attempt");
    TreeItem<String> rootItem = new TreeItem<String>("Dataset root");
    rootItem.setExpanded(true);
    final TreeView<String> tree = new TreeView<String>(rootItem);
    final TreeItem<String> testResultsItem = new TreeItem<String>(
        "Test Results");
    rootItem.getChildren().add(testResultsItem);
    testResultsItem.setExpanded(true);
    final CheckBoxTreeItem<String> normalTreeItem = new CheckBoxTreeItem<String>(
        "Normal");
    testResultsItem.getChildren().add(normalTreeItem);
    final CheckBoxTreeItem<String> abnormalTreeItem = new CheckBoxTreeItem<String>(
        "Abnormal");
    testResultsItem.getChildren().add(abnormalTreeItem);
    final CheckBoxTreeItem<String> preTreeItem = new CheckBoxTreeItem<String>(
        "PreCancer");
    testResultsItem.getChildren().add(preTreeItem);
    final CheckBoxTreeItem<String> cancerTreeItem = new CheckBoxTreeItem<String>(
        "Cancer");
    testResultsItem.getChildren().add(cancerTreeItem);
    // tree.setCellFactory(CheckBoxTreeCell.<String>forTreeView());
    tree.setCellFactory(new Callback<TreeView<String>, TreeCell<String>>() {
      @Override
      public TreeCell<String> call(TreeView<String> param) {
        return new TreeCell<String>() {
          @Override
          public void updateItem(String item, boolean empty) {
            super.updateItem(item, empty);
            if (empty) {
              setText(null);
              setGraphic(null);
            } else {
              TreeItem<String> treeItem = getTreeItem();
              if (treeItem instanceof CheckBoxTreeItem) {
                CheckBoxTreeItem<String> cbTreeItem = (CheckBoxTreeItem<String>) treeItem;
                setText(item.toString());
                CheckBox cb = new CheckBox();
                cb.indeterminateProperty().bindBidirectional(
                    cbTreeItem.indeterminateProperty());
                cb.selectedProperty().bindBidirectional(
                    cbTreeItem.selectedProperty());
                setGraphic(cb);
              } else {
                setText(item.toString());
                setGraphic(null);
    tree.setRoot(rootItem);
    tree.setShowRoot(true);
    StackPane root = new StackPane();
    root.getChildren().add(tree);
    primaryStage.setScene(new Scene(root, 300, 250));
    primaryStage.show();
}I haven't tested this out much but it seems to work. There might be an easier way but I don't see it.