对象类型的 JTree 显示对象的一些属性，但选择时返回整个对象

Question

我有一个向 jtree 添加问题的程序。 Jtree 上的每个问题都是 Question 类型，具有 3 个属性；名称、ID 和问题文本。我希望我的jtree仅显示问题名称，但选择节点时，它应该在文本框中显示QuestText。

问题是 Jtree 按我的意愿显示问题的名称，但是当我选择树的一个节点时，我得到一个 ClassCastException。这是因为我的 treeSelectionListener 方法中的 getUserObject() 。它获取 getUserObject() 返回的字符串并尝试将其转换为 Question 类。如何在没有 getUserObject() 的情况下获取所选字符串的 Question 类属性，例如 questionText 或 id，或者是否有另一种方式来表示这棵树？

这是我的代码：

public class Question 
{
 public String name;
 public String id;
 public String qText;  
 public Question(String name,String id, String text) 
 {
        this.name = name;
        this.id = id;
        this.qText = text;
 }

 public String getQuestion()
 { return qText; }

 public String getName()
 { return name;}

 public String getId()
 { return id;}

 public void setQuestionText(String text)
 { qText= text; }

 public void setId(String uid)
 { id = uid;}

 @Override
 public String toString() 
 { return   name; }
}

创建树的部分代码：

public Question rootQ = new Question("Questions", UUID.randomUUID().toString(), "What is your name?");
public DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode(rootQ.toString());
public JTree tree = new JTree(rootNode);

initialise(){
 //....other code to initilise
 panel.add(new JScrollPane(tree));
 tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
 tree.setShowsRootHandles(true);
 tree.addTreeSelectionListener(treeMenuClicked);
 tree.setRootVisible(true);
 tree.setVisible(true);
 panel.add(addChild());
}

public TreeSelectionListener treeMenuClicked = new TreeSelectionListener() 
{

public void valueChanged(TreeSelectionEvent e) 
{
    TreePath currentSelection = tree.getSelectionPath();
    if(currentSelection != null){
     DefaultMutableTreeNode currentNode =  (DefaultMutableTreeNode)currentSelection.getLastPathComponent();
     Object nodeInfo = currentNode.getUserObject();
     Question questionText = (Question)nodeInfo;
     txtQuestion.setText(questionText.getQuestion()); 
    }
}};

public JButton addChild()
{
    JButton btnAddChild = new JButton("Add Child");
    btnAddChild.addActionListener(new ActionListener() 
    {
        public void actionPerformed(ActionEvent arg0) 
        {   String userQuestion = txtQuestion.getText();
            TreePath currentSelection = tree.getSelectionPath();
            if (currentSelection != null) {
                Question createdQuestion = new Question(userQuestion,UUID.randomUUID().toString(),userQuestion);
                DefaultMutableTreeNode currentNode = (DefaultMutableTreeNode) currentSelection.getLastPathComponent();
                DefaultTreeModel model = ((DefaultTreeModel) tree.getModel());
                DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(createdQuestion.toString());
                currentNode.add(newNode);
                model.nodeStructureChanged(currentNode);
            }
        }});
    btnAddChild.setBounds(609, 374, 117, 47);
    return btnAddChild;
}

Answer 1

就像@Ajay 用他的评论暗示的那样，而不是

DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(createdQuestion.toString());

简单地做

DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(createdQuestion);

您是当前将您的用户对象设置为字符串的人，而不是 API。

另外，你可以通过tree.getLastSelectedPathComponent()获取选择的节点，而不是总是获取选择路径然后调用TreePath.getLastPathComponent()。

public void valueChanged(TreeSelectionEvent e) 
{
    DefaultMutableTreeNode currentNode = (DefaultMutableTreeNode)tree.getLastSelectedPathComponent();
    if(currentNode != null){         
        Object nodeInfo = currentNode.getUserObject();
        Question questionText = (Question)nodeInfo;
        txtQuestion.setText(questionText.getQuestion()); 
    }
}};