限制添加 JTree 的节点，但第一级子节点除外

Question

我一直在尝试很多方法来限制我的代码仅将节点添加到第一级。这意味着用户只能将节点添加到 JTree 的第一级子节点。

在我的程序中添加节点可以通过两种方式完成 1.添加节点按钮 2. Select > 右键单击 > 添加节点（在这里，如果选择了非一级子节点，我想禁用此行为。虽然这是一个远景）

我需要一个允许在其他级别添加节点的验证。谢谢！

这是工作代码：

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JPopupMenu;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeNode;
import javax.swing.tree.TreePath;

public class ProblemTree extends JFrame {

    private DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
    private DefaultTreeModel model = new DefaultTreeModel(root);
    private JTree tree = new JTree(model);
    private JButton addButton = new JButton("Add Node to 1st level only");

    public ProblemTree() {
        DefaultMutableTreeNode n1 = new DefaultMutableTreeNode(
                "1st level: Child 1");
        n1.add(new DefaultMutableTreeNode("2nd level: Child l"));
        DefaultMutableTreeNode n2 = new DefaultMutableTreeNode(
                "1st level: Child 2");
        n2.add(new DefaultMutableTreeNode("2nd level: Child 2"));
        DefaultMutableTreeNode n3 = new DefaultMutableTreeNode(
                "1st level: Child 3");
        n3.add(new DefaultMutableTreeNode("2nd level: Child 3"));

        root.add(n1);
        root.add(n2);
        root.add(n3);

        tree.setEditable(true);
        tree.setSelectionRow(0);
        tree.setRootVisible(true);
        tree.setShowsRootHandles(true);

        final JPopupMenu popupMenu = new JPopupMenu();
        JMenuItem runTask = new JMenuItem("New Node for 1st level only =( ");
        runTask.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                DefaultMutableTreeNode selNode = (DefaultMutableTreeNode) tree
                        .getLastSelectedPathComponent();
                if (selNode == null) {
                    return;
                }
                DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(
                        "New Node");
                model.insertNodeInto(newNode, selNode, selNode.getChildCount());

                TreeNode[] nodes = model.getPathToRoot(newNode);
                TreePath path = new TreePath(nodes);
                tree.scrollPathToVisible(path);
                tree.setSelectionPath(path);
                tree.startEditingAtPath(path);
            }
        });
        popupMenu.add(runTask);
        tree.setComponentPopupMenu(popupMenu);

        JScrollPane scrollPane = new JScrollPane(tree);
        getContentPane().add(scrollPane, BorderLayout.CENTER);

        JPanel panel = new JPanel();

        addButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                DefaultMutableTreeNode selNode = (DefaultMutableTreeNode) tree
                        .getLastSelectedPathComponent();
                if (selNode == null) {
                    return;
                }
                DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(
                        "New Node");
                model.insertNodeInto(newNode, selNode, selNode.getChildCount());

                TreeNode[] nodes = model.getPathToRoot(newNode);
                TreePath path = new TreePath(nodes);
                tree.scrollPathToVisible(path);
                tree.setSelectionPath(path);
                tree.startEditingAtPath(path);
            }
        });
        panel.add(addButton);

        getContentPane().add(panel, BorderLayout.SOUTH);
        setSize(700, 400);
        setVisible(true);
    }

    public static void main(String[] arg) {
        ProblemTree pt = new ProblemTree();
    }
}

Answer 1

只需替换

tree.setComponentPopupMenu(popupMenu);

与：

tree.addMouseListener(new MouseAdapter() {
    @Override
        public void mousePressed(MouseEvent e) {
        if (SwingUtilities.isRightMouseButton(e)) {
            int row = tree.getClosestRowForLocation(e.getX(), e.getY());
            tree.setSelectionRow(row);
            if (tree.getSelectionPath().getPathCount() == 2) {
                popupMenu.show(e.getComponent(), e.getX(), e.getY());
            }
        }
    }
});

并控制您的按钮添加：

addButton.setEnabled(false);
tree.addTreeSelectionListener(new TreeSelectionListener() {
    @Override
    public void valueChanged(TreeSelectionEvent e) {
        addButton.setEnabled((tree.getSelectionPath().getPathCount() == 2));
    }
});

限制添加 JTree 的节点，但第一级子节点除外

Restricting the addition of nodes of a JTree except for the 1st level child

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