java为什么我不能将根添加到JTree？

Question

我试着做jtreejt=newjtree（root）；运行它，它说

"The constructor JTree(DefaultMutableTreeNode) is undefined".

这是我的代码截图-https://snipboard.io/hwU4b7.jpg

import javax.swing.JFrame;
import javax.swing.tree.DefaultMutableTreeNode;

public class JTreeInfo {

    JFrame frame;
        
    JTreeInfo() {
        frame = new JFrame();   

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("hmtl");
        DefaultMutableTreeNode n1 = new DefaultMutableTreeNode("head");
        DefaultMutableTreeNode n2 = new DefaultMutableTreeNode("body");
        root.add(n1);
        root.add(n2);
        DefaultMutableTreeNode meta = new DefaultMutableTreeNode("meta");
        DefaultMutableTreeNode title = new DefaultMutableTreeNode("title");
        n1.add(meta);
        n1.add(title);
        DefaultMutableTreeNode ul = new DefaultMutableTreeNode("ul");
        DefaultMutableTreeNode hl = new DefaultMutableTreeNode("hl");
        DefaultMutableTreeNode h2 = new DefaultMutableTreeNode("h2");
        n2.add(ul);
        n2.add(hl);
        n2.add(h2);
        DefaultMutableTreeNode li = new DefaultMutableTreeNode("li");
        DefaultMutableTreeNode li2 = new DefaultMutableTreeNode("li");
        ul.add(li);
        ul.add(li2);
        DefaultMutableTreeNode a = new DefaultMutableTreeNode("a");
        h2.add(a);

        JTree jt = new JTree(root); 
        frame.add(jt);
        frame.setSize(500,500);
        frame.setTitle("JTree");
        frame.isVisible(true);
    }

    public static void main(String[] args) {

        new JTreeInfo();

    }
}

Answer 1

确保导入的包正确。一个像样的IDE将允许您自动完成这项工作

还应该将JTree嵌入JScrollPane中，否则会遇到一些有趣的视觉问题

import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                DefaultMutableTreeNode root = new DefaultMutableTreeNode("hmtl");
                DefaultMutableTreeNode n1 = new DefaultMutableTreeNode("head");
                DefaultMutableTreeNode n2 = new DefaultMutableTreeNode("body");
                root.add(n1);
                root.add(n2);
                DefaultMutableTreeNode meta = new DefaultMutableTreeNode("meta");
                DefaultMutableTreeNode title = new DefaultMutableTreeNode("title");
                n1.add(meta);
                n1.add(title);
                DefaultMutableTreeNode ul = new DefaultMutableTreeNode("ul");
                DefaultMutableTreeNode hl = new DefaultMutableTreeNode("hl");
                DefaultMutableTreeNode h2 = new DefaultMutableTreeNode("h2");
                n2.add(ul);
                n2.add(hl);
                n2.add(h2);
                DefaultMutableTreeNode li = new DefaultMutableTreeNode("li");
                DefaultMutableTreeNode li2 = new DefaultMutableTreeNode("li");
                ul.add(li);
                ul.add(li2);
                DefaultMutableTreeNode a = new DefaultMutableTreeNode("a");
                h2.add(a);

                JTree jt = new JTree(root);

                JFrame frame = new JFrame();
                frame.add(new JScrollPane(jt));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}