嵌套JavaFX TreeView的有效填充

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class TreeViewExample extends Application {

    @Override
    public void start(Stage primaryStage) {
        // 创建根节点
        TreeItem<String> rootItem = new TreeItem<>("Root");
        rootItem.setExpanded(true); // 默认展开根节点

        // 添加子节点
        for (int i = 1; i <= 3; i++) {
            TreeItem<String> item = new TreeItem<>("Item " + i);
            rootItem.getChildren().add(item);

            // 添加子节点的子节点
            for (int j = 1; j <= 2; j++) {
                TreeItem<String> subItem = new TreeItem<>("SubItem " + i + "." + j);
                item.getChildren().add(subItem);
            }
        }

        // 创建TreeView并设置根节点
        TreeView<String> tree = new TreeView<>(rootItem);

        // 创建布局并添加TreeView
        StackPane root = new StackPane();
        root.getChildren().add(tree);

        // 设置场景并显示窗口
        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.setTitle("TreeView Example");
        primaryStage.show();
    }

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

tree.setCellFactory(param -> new TreeCell<String>() {
    @Override
    protected void updateItem(String item, boolean empty) {
        super.updateItem(item, empty);
        if (empty || item == null) {
            setText(null);
        } else {
            setText(item);
        }
    }
});

rootItem.addEventHandler(TreeItem.branchExpandedEvent(), event -> {
    TreeItem<String> item = event.getTreeItem();
    if (item.getChildren().isEmpty()) {
        // 模拟加载子节点
        for (int i = 1; i <= 2; i++) {
            TreeItem<String> subItem = new TreeItem<>("Lazy SubItem " + item.getValue() + "." + i);
            item.getChildren().add(subItem);
        }
    }
});