java - 使用自定义树模型添加 Swing 树选择监听器

Question

我现在正在学习 java，我的应用程序之一是简单的 Swing 文件层次结构查看器，它使用 JTree 小部件。我的问题是如何添加 Jtree 鼠标选择事件监听器(例如将节点文本值记录到控制台)如果我以这种方式实现 TreeModel(示例来自《Java Foundation Classes in a Nutshell》一书):

    public class FileTreeDemo {
    public static void main(String[] args) {
        File root;
        if (args.length > 0)
            root = new File(args[0]);
        else
            root = new File(System.getProperty("user.home"));

                FileTreeModel model = new FileTreeModel(root);

        MyJtree tree = new MyJtree();
        tree.setModel(model);

        JScrollPane scrollpane = new JScrollPane(tree);

        JFrame frame = new JFrame("FileTreeDemo");
        frame.getContentPane().add(scrollpane, "Center");
        frame.setSize(400, 600);
        frame.setVisible(true);
    }
}

class FileTreeModel implements TreeModel {
    protected File root;

    public FileTreeModel(File root) {
        this.root = root;
    }

    public Object getRoot() {
        return root;
    }

    public boolean isLeaf(Object node) {
        return ((File) node).isFile();
    }

    public int getChildCount(Object parent) {
        String[] children = ((File) parent).list();
        if (children == null)
            return 0;
        return children.length;
    }

    public Object getChild(Object parent, int index) {
        String[] children = ((File) parent).list();
        if ((children == null) || (index >= children.length))
            return null;
        return new File((File) parent, children[index]);
    }

    public int getIndexOfChild(Object parent, Object child) {
        String[] children = ((File) parent).list();
        if (children == null)
            return -1;
        String childname = ((File) child).getName();
        for (int i = 0; i < children.length; i++) {
            if (childname.equals(children[i]))
                return i;
        }
        return -1;
    }

    public void valueForPathChanged(TreePath path, Object newvalue) {
    }

    public void addTreeModelListener(TreeModelListener l) {
    }

    public void removeTreeModelListener(TreeModelListener l) {
    }
}

这里我尝试通过 MyJtree 扩展 JTree 类并添加 AddTreeSelectionListener

public class MyJtree extends JTree {
    public MyJtree() {
        super();
        this.addTreeSelectionListener(new TreeSelectionListener() {
            public void valueChanged(TreeSelectionEvent e) {
                DefaultMutableTreeNode node = (DefaultMutableTreeNode) e
                        .getPath().getLastPathComponent();
                System.out.println("You selected " + node);
            }
        });
    }
}

但是当我点击 JTree 项目时，我得到了这个:

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.io.File cannot be cast to javax.swing.tree.DefaultMutableTreeNode

那么，我应该如何解决这个问题？

Answer 1

不会在监听器中转换为 DefaultMutableTreeNode。 getLastPathComponent 方法从您的 TreeModel 返回一个元素，在您的例子中是一个 File

堆栈跟踪和异常消息对此非常清楚