java - JTree的动态初始化

Question

谈到 JTree 时，我已经用头撞砖墙好几天了!

我想创建一个 JTree，它在运行时从 mp3 标签动态获取其内容。到目前为止一切顺利，除了在填充 JTree 时我非常头疼。经过多次实验，我终于放弃并寻求帮助。我一直在使用下面创建的类来尝试将子节点添加到 JTree 中现有节点的方法。我遇到的问题是在 try block 内，类型不兼容。我收到的错误是:

error: incompatible types: `TreeNode` cannot be converted to `MutableTreeNode`

treeModel.insertNodeInto 需要 MutableTreeNode 作为其第二个参数。我用来获取第二个参数的父节点的方法 rootNode.getChildAt() 返回 TreeNode。

还有这个吗？？？现在有人知道为什么 getChildAt() 返回一个 TreeNode 对象而不是 DefaulMutableTreeNode 吗？对象类型 rootNode 已初始化作为？？？

package jtreeex;

import java.util.Enumeration;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeSelectionModel;

/**
 *
 * @author david
 */
public class JTreeEx implements Runnable
{

    public JTreeEx()
    {
        JFrame jfrm = new JFrame();  
        JPanel panel = new JPanel();
        JTree tree;

        DefaultMutableTreeNode rootNode;
        rootNode = new DefaultMutableTreeNode("Audio");
        DefaultTreeModel treeModel = new DefaultTreeModel(rootNode);
        treeModel.addTreeModelListener(new MyTreeModelListener());

        tree = new JTree(treeModel);
        tree.setEditable(true);
        tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
        tree.setShowsRootHandles(true);
        String [] anArray = {"Dogs", "Cats"};


        // Inserts new root nodes from anArray
        for(int i = 0; i < anArray.length; i++)
        {
            treeModel.insertNodeInto(new DefaultMutableTreeNode(anArray[i]), 
                    rootNode, rootNode.getChildCount());

        }

        // Get enumeration of children of rootNode
        Enumeration eNum = rootNode.children();

        try
        {
            while(eNum.hasMoreElements() == true)
            {
                treeModel.insertNodeInto(new DefaultMutableTreeNode("Toby"), 
                        rootNode.getChildAt(1), rootNode.getChildCount());
            }
        }
        catch (Exception e)
        {
            System.out.println("no enums left");
        }

        panel.add(tree);

        jfrm.add(panel);
        jfrm.setSize(400,200);
        jfrm.setVisible(true);
        jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here

        (new Thread(new JTreeEx())).start();
    }

    public void run()
    {

    }

}

Answer 1

treeModel.insertNodeInto requires MutableTreeNode for its second argument. The method im using to get the parent node for the second argument, rootNode.getChildAt() returns TreeNode.

您正在构建树，并且知道正在将 DefaultMutableTreeNode 插入到树中，因此只需将 TreeNode 转换为 DefaultMutableTreeNode:

treeModel.insertNodeInto(new DefaultMutableTreeNode("Toby"), 
    (DefaultMutableTreeNode)rootNode.getChildAt(1), rootNode.getChildCount());