将子节点添加到JTree的父节点

Question

我使用Swing控件创建了一个JTree，名为treeWorld。其根节为根和儿童，即哺乳动物、鸟类、爬行动物、两栖动物、昆虫。现在我想添加麻雀，布谷鸟到鸟类编程。

但我不能把麻雀，布谷鸟加到鸟身上。

这是我的代码：

DefaultTreeModel model = (DefaultTreeModel)treeWorld.getModel();

DefaultMutableTreeNode root = (DefaultMutableTreeNode) model.getRoot();

DefaultMutableTreeNode bird = new DefaultMutableTreeNode("Birds");
DefaultMutableTreeNode sparrow = new DefaultMutableTreeNode("sparrow");

DefaultMutableTreeNode cuckoo = new DefaultMutableTreeNode("cuckoo");
bird.add(sparrow);
bird.add(cuckoo);
this.pack();
this.setVisible(true);

Answer 1

似乎您从未将bird节点添加到您的JTree中的问题，请使用root.add(bird);。

如果根节点已经包含了鸟类节点，则需要在root中搜索该节点，而不是创建新的节点。

如果将新节点添加到可见树中，也可以使用model.nodesWereInserted(NODE, new int[]NODE.getChildCount()-1});。添加新子节点的NODE节点。

示例：

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

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;

public class TestFrame extends JFrame {

    private JTree t;

    public TestFrame() {
        init();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setLocationRelativeTo(null);
        setVisible(true);
    }

    private void init() {

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("root");
        DefaultMutableTreeNode bird = new DefaultMutableTreeNode("Birds");
        root.add(bird);

        DefaultTreeModel model = new DefaultTreeModel(root);
        add(t=new JTree(model));

        JButton btn = new JButton("add");
        btn.addActionListener(getAddListener());

        add(btn,BorderLayout.SOUTH);
    }

    private ActionListener getAddListener() {
        return new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                DefaultTreeModel model = (DefaultTreeModel)t.getModel();
                DefaultMutableTreeNode root = (DefaultMutableTreeNode) model.getRoot();

                Enumeration children = root.children();
                while(children.hasMoreElements()){
                    DefaultMutableTreeNode node = (DefaultMutableTreeNode) children.nextElement();
                    if(node.toString().equals("Birds")){

                        DefaultMutableTreeNode sparrow = new DefaultMutableTreeNode("sparrow");
                        DefaultMutableTreeNode cuckoo = new DefaultMutableTreeNode("cuckoo");

                        node.add(sparrow);
                        node.add(cuckoo);
                        model.nodesWereInserted(node, new int[]{node.getChildCount()-1,node.getChildCount()-2});
                        break;
                    }
                }


            }
        };
    }

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

}

Answer 2

我不确定，因为您还没有发布完整的可运行示例，但我认为，您只需更新您的模型。

bird.add(sparrow);
bird.add(cuckoo);
model.reload(); // your model and tree don't know that you've added some nodes.
this.pack();
this.setVisible(true);