使用public void updateItem（String item，boolean empty）方法在javafx中的treeView中键入转换错误

Question

我是JavaFx的新手。在树视图中，如果我添加一个stringItem的字符串（TreeItem<String>），我们就可以使用以下代码编辑，添加或删除节点。

treeView.setCellFactory(new Callback<TreeView<String>,TreeCell<String>>(){
    @Override
    public TreeCell<String> call(TreeView<String> p) {
        return new TextFieldTreeCellImpl(treeView);
    }
});

但是如果treeItems可以是任何类型（TreeItem<?>），我们可以获取树但无法查看，无法添加或删除节点。它抛出了类型转换错误。请分享你的建议。我的代码如下， 在这里

public TreeItem<?>     root;

    TreeView<String> treeView = new TreeView<String>((TreeItem<String>) tree.root);
    treeView.setEditable(true);
    treeView.setCellFactory(new Callback<TreeView<String>,TreeCell<String>>(){
        @Override
        public TreeCell<String> call(TreeView<String> p) {
            return new TextFieldTreeCellImpl(treeView);
        }
    });

    box.getChildren().add(treeView);
    stage.setScene(scene);
    stage.show();
}

private final class TextFieldTreeCellImpl extends TreeCell<String> {

    private TextField textField;
    private ContextMenu addMenu = new ContextMenu();

    public TextFieldTreeCellImpl(TreeView<String> p) {
        MenuItem addMenuItem = new MenuItem("Add Nodes");
        MenuItem deleteMenuItem = new MenuItem("Delete Nodes");
        addMenu.getItems().add(addMenuItem);
        addMenu.getItems().add(deleteMenuItem);
        addMenuItem.setOnAction(new EventHandler() {
            public void handle(Event t) {
                TreeItem newNodes =  p.getSelectionModel().getSelectedItem();
                boolean remove = newNodes.getParent().getChildren().add(newNodes);
            }
        });
        deleteMenuItem.setOnAction(new EventHandler() {
            public void handle(Event t) {
                TreeItem removeNodes =  p.getSelectionModel().getSelectedItem();
                boolean remove = removeNodes.getParent().getChildren().remove(removeNodes);
                System.out.println("Remove");
            }
        });
    }

    @Override
    public void startEdit() {
        super.startEdit();

        if (textField == null) {
            createTextField();
        }
        setText(null);
        setGraphic(textField);
        textField.selectAll();
    }

    @Override
    public void cancelEdit() {
        super.cancelEdit();

        setText((String) getItem());
        setGraphic(getTreeItem().getGraphic());
    }

    @Override
    public void updateItem(String item, boolean empty) {
        super.updateItem(item, empty);

       if (empty) {
            setText(null);
            setGraphic(null);
        } else {
            if (isEditing()) {

                if (textField != null) {

                    textField.setText(getString());
//              }
//              setText(null);

                setGraphic(textField);

            } else {

                setText(getString());

                setGraphic(getTreeItem().getGraphic());
                if (
                    !getTreeItem().isLeaf()&&getTreeItem().getParent()!= null
                ){

                    setContextMenu(addMenu);

                }

            }

        }
    }

    private void createTextField() {
        textField = new TextField(getString());
        textField.setOnKeyReleased(new EventHandler<KeyEvent>() {

            @Override
            public void handle(KeyEvent t) {
                if (t.getCode() == KeyCode.ENTER) {
                    commitEdit(textField.getText());
                } else if (t.getCode() == KeyCode.ESCAPE) {
                    cancelEdit();
                }
            }
        });  

    }

    private String getString() {
        return getItem() == null ? "" : getItem().toString();
    }
}