java - 如何在 JTree 上显示动态更新？/如何刷新或重新加载 JTree？

Question

应用简单，一个框架中有两个面板

1. 第一个面板，从数据库中检索所有学生，使用多个 hashmap 获取父子排列并将其显示在树上。

2. 第二个面板，当您点击一个学生时，该学生的所有详细信息 (selectionlistener) 都会显示在文本框中。

现在，当我在第二个面板上更改学生的姓名时，数据库会正确更新它，但树显示旧值。

我试过 treepanel.reload()，我试过 treemodellistener。

谁能帮帮我。在网上浏览了很多解决方案，都是部分的，我无法将其应用到我的代码中。

提前致谢。

---

主框架.java

/**
 * @author Suraj Baliga
 * 
 * Returns a JFrame with two Panels one having the Jtree and other 
 * having the details of the selected tree component.It also has dynamic tree and 
 * dynamic textbox where updation of text in the textbox will change the value in 
 * databse on click of save button.The JDBC localhost url may change with each machine 
 * as the database location and port number may vary.
*/




package Student_Details;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Set;
import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import org.apache.commons.collections.MultiHashMap;

public final class Main_frame extends JPanel 
{
    String sname,sschool;

    ArrayList StudName_arrylst = new ArrayList();
    ArrayList SchlName_arrylst = new ArrayList();
    ArrayList StudDetailTxtFld_arrylst = new ArrayList();


    static public Connection connect,connect_update;
    public ResultSet resultSet;
    public static ResultSet resultset2;
    MultiHashMap SchlStud_hashmap = new MultiHashMap();

    int i,j,k,k2,z;

    DefaultMutableTreeNode tree_parent;
    int SchlName_arylist_length, StudNamearrylst_length;
    private tree_generation treePanel;


    static JButton save_button = new JButton("Save");
    static JButton cancel_button = new JButton("Cancel");

    static JTextField studName_txtbox= new JTextField();
    static JTextField studAddress_txtbox = new JTextField();
    static JTextField studOthr_txtbox = new JTextField();

   static public String user_name;
   static public String user_add;
   static public String user_other;




    static JLabel name_label = new JLabel("Name : ");
    static JLabel address_label = new JLabel("Adress : ");
    static JLabel other_label = new JLabel("Other Deatils : ");

   static String studDetailsTxtbox_disp[] = new String[10];
    static String studDetailsTxtbx_disp_db[] = new String[10];
    static String studDetailsTxtbxchange[] = new String[10];

    public JPanel panel;
    static JPanel panel_boxes = new JPanel();




    public Main_frame() 
    {

        super(new BorderLayout());

        //Create the components.
        treePanel = new tree_generation();
        populateTree(treePanel);

        //Lay everything out.
        treePanel.setPreferredSize(new Dimension(300, 150));
        add(treePanel, BorderLayout.WEST);

        panel = new JPanel(new GridLayout(1, 2));
        add(panel, BorderLayout.CENTER); 
     }






    public void populateTree(tree_generation treePanel) 
    {
        try 
        {
            Class.forName("org.apache.derby.jdbc.ClientDriver");
            connect = DriverManager.getConnection("jdbc:derby://localhost:1527/treedata2", "suraj", "suraj");
            PreparedStatement AllStuddetails = connect.prepareStatement("SELECT * from student_details");
            resultSet = AllStuddetails.executeQuery();
            while (resultSet.next()) 
            {

                sname = resultSet.getString(1);
                sschool = resultSet.getString(3);
                SchlStud_hashmap.put(sschool, sname);
            }
        } 
        catch (Exception e) 
         {

         }
        Set keySet = SchlStud_hashmap.keySet();
        Iterator keyIterator = keySet.iterator();

        while (keyIterator.hasNext())
        {
            Object key = keyIterator.next();
            SchlName_arrylst.add(key);

            Collection values = (Collection) SchlStud_hashmap.get(key);
            Iterator valuesIterator = values.iterator();

            while (valuesIterator.hasNext()) 
            {
                StudName_arrylst.add(valuesIterator.next());

            }
            SchlName_arylist_length = SchlName_arrylst.size();
            StudNamearrylst_length = StudName_arrylst.size();

            String schlname_tree[] = new String[SchlName_arylist_length];
            String studname_tree[] = new String[StudNamearrylst_length];

            Iterator SchlName_iterator = SchlName_arrylst.iterator();

            i = 0;
            while (SchlName_iterator.hasNext()) 
            {
                schlname_tree[i] = SchlName_iterator.next().toString();
            }

            Iterator StudName_iterator = StudName_arrylst.iterator();
            j = 0;
            while (StudName_iterator.hasNext()) 
            {
                studname_tree[j] = StudName_iterator.next().toString();
                 j++;
            }

            for (k = 0; k < schlname_tree.length; k++) 
            {
                  tree_parent = treePanel.addObject(null, schlname_tree[k]);
                  for (k2 = 0; k2 < studname_tree.length; k2++) 
                     {
                            treePanel.addObject(tree_parent, studname_tree[k2]);
                     }
            }
           StudName_arrylst.clear();
           SchlName_arrylst.clear();
         }

  }







    /**
     * Create the GUI and show it.  
     */
    private static void createAndShowGUI() 
    {
        //Create and set up the window.
        JFrame frame = new JFrame("Student Details");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        Main_frame newContentPane = new Main_frame();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);
        panel_boxes.setLayout(null);

        name_label.setBounds(55,90,150,100);   
        studName_txtbox.setBounds(225,130, 155, 25);
        panel_boxes.add(name_label);
        panel_boxes.add(studName_txtbox);


        address_label.setBounds(55,160, 150, 100);
        studAddress_txtbox.setBounds(225,200, 155, 25);
        panel_boxes.add(address_label);
        panel_boxes.add(studAddress_txtbox);

        other_label.setBounds(55,220, 150, 100);
        studOthr_txtbox.setBounds(225,270, 155, 25);
        panel_boxes.add(other_label); 
        panel_boxes.add(studOthr_txtbox);


        save_button.setBounds(150,350, 100, 50);
        cancel_button.setBounds(350,350, 100, 50);
        panel_boxes.add(save_button);
        panel_boxes.add(cancel_button); 

        frame.add(panel_boxes); 
        //Display the window.
        frame.pack();
        frame.setSize(1000,700);
        frame.setVisible(true);


        save_button.setEnabled(false);
        cancel_button.setEnabled(false);


         studName_txtbox.addFocusListener(new FocusListener() 
         {
            @Override //since some additional functionality is added by the user to 
                      //the inbuilt function @override notation is used
            public void focusGained(FocusEvent e) 
            {
             save_button.setEnabled(true);
             cancel_button.setEnabled(true);
            }

            @Override
            public void focusLost(FocusEvent e) 
            {
                System.out.println("out of focus textbox");
            }


        });

          studAddress_txtbox.addFocusListener(new FocusListener() {

            @Override
            public void focusGained(FocusEvent e) 
            {
             save_button.setEnabled(true);
             cancel_button.setEnabled(true);    
            }

            @Override
            public void focusLost(FocusEvent e) 
            {
               save_button.setEnabled(false);
                cancel_button.setEnabled(false); 
            }
        });


            studOthr_txtbox.addFocusListener(new FocusListener() {

            @Override
            public void focusGained(FocusEvent e) 
            {
             save_button.setEnabled(true);
             cancel_button.setEnabled(true);    
            }

            @Override
            public void focusLost(FocusEvent e) 
            {
               save_button.setEnabled(false);
                cancel_button.setEnabled(false); 
            }
        });

             cancel_button.addActionListener(new ActionListener() 
        { 
                public void actionPerformed(ActionEvent e) 
                { 
                    if(e.getSource()== cancel_button )
                    {
                 clear_textboxes();
                 }
                }
              } );
            save_button.addActionListener(new ActionListener() 
        { 
                public void actionPerformed(ActionEvent e) 
                { 
                    if(e.getSource()== save_button )
                    {
                 selectionButtonPressed();
                 }
                }
              } );
    }




     public void fill_textboxes(ArrayList a1)
    {
        Iterator alldetails = a1.iterator();
        z=0;
        while (alldetails.hasNext()) 
         {
          studDetailsTxtbx_disp_db[z]= (String) alldetails.next();
          System.out.println("this is the Detail : "+studDetailsTxtbx_disp_db[z]);
           z++;   
         }  

     studName_txtbox.setText(studDetailsTxtbx_disp_db[0]);
     studAddress_txtbox.setText(studDetailsTxtbx_disp_db[1].toString());
     studOthr_txtbox.setText(studDetailsTxtbx_disp_db[2]);

 }
  public static void selectionButtonPressed()
    {
      studDetailsTxtbxchange[0]=studName_txtbox.getText(); 
      studDetailsTxtbxchange[1]=studAddress_txtbox.getText();
      studDetailsTxtbxchange[2]=studOthr_txtbox.getText();
      try 
        {
            if((studDetailsTxtbxchange[0].equals(""))||(studDetailsTxtbxchange[0] == null)||(studDetailsTxtbxchange[1].equals(""))||(studDetailsTxtbxchange[1] == null)||(studDetailsTxtbxchange[2].equals(""))||(studDetailsTxtbxchange[2] == null))
            {
            JOptionPane.showMessageDialog(null,"One of the Fields is Blank","Error",JOptionPane.ERROR_MESSAGE);
            }
            else
            {
            System.out.println("control here inside else baby..that has : : "+studDetailsTxtbxchange[0]);
            Class.forName("org.apache.derby.jdbc.ClientDriver");
            connect_update = DriverManager.getConnection("jdbc:derby://localhost:1527/treedata2", "suraj", "suraj");
            PreparedStatement execqry = connect.prepareStatement("select * from student_details where student_name='"+studDetailsTxtbxchange[0]+"'");
            resultset2=execqry.executeQuery();
             System.out.println("control at end if else");
            if(resultset2.next())
            {
                JOptionPane.showMessageDialog(null,"Sorry This name already exists","Error",JOptionPane.ERROR_MESSAGE);
            }
            else
            {
               System.out.println("control here");
               Class.forName("org.apache.derby.jdbc.ClientDriver");
               connect_update = DriverManager.getConnection("jdbc:derby://localhost:1527/treedata2", "suraj", "suraj");
               PreparedStatement updateQry = connect.prepareStatement("UPDATE student_details SET student_name='"+studDetailsTxtbxchange[0]+"',student_address='"+studDetailsTxtbxchange[1]+"',student_school='"+studDetailsTxtbxchange[2]+"' WHERE student_name='"+user_name+"' and student_address='"+user_add+"'and student_school='"+user_other+"'");
               updateQry.executeUpdate();
               JOptionPane.showMessageDialog(null,"Record Updated!","UPDATED",JOptionPane.OK_OPTION);
                  tree_generation.loadit();
            }

            } 

        }
        catch (Exception e) 
         {
           e.printStackTrace(); 
         }              
    }

  public static void clear_textboxes() 
     {
     studName_txtbox.setText(studDetailsTxtbx_disp_db[0]);
     studAddress_txtbox.setText(studDetailsTxtbx_disp_db[1].toString());
     studOthr_txtbox.setText(studDetailsTxtbx_disp_db[2]);
     }

    void dbaction(String string)
      {

      studDetailsTxtbox_disp[0]= string;
      System.out.println("This is the stuff :" + studDetailsTxtbox_disp[0]);
       try
       {
       Class.forName("org.apache.derby.jdbc.ClientDriver").newInstance();
       connect = DriverManager.getConnection("jdbc:derby://localhost:1527/treedata2","suraj","suraj");
       PreparedStatement statement4 = connect.prepareStatement("SELECT * from student_details where student_name ='"+studDetailsTxtbox_disp[0]+"'");                
       resultSet = statement4.executeQuery();
       while(resultSet.next())
                   {

                             user_name = resultSet.getString("student_name");
                            StudDetailTxtFld_arrylst.add(user_name);
                            System.out.println("name :"+user_name);

                            user_add = resultSet.getString("student_address");
                            StudDetailTxtFld_arrylst.add(user_add);
                            System.out.println("address : "+ user_add);


                            user_other = resultSet.getString("student_school");
                            StudDetailTxtFld_arrylst.add(user_other);
                            System.out.println("school : "+user_other);
                 }

    }
    catch (Exception e1) 
    {
        e1.printStackTrace();
    }
   fill_textboxes(StudDetailTxtFld_arrylst);
 }




    public static void main(String[] args) 
    {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            public void run() 
            {
                createAndShowGUI();
            }
        });
    }
}

---

tree_generation.java

/**
 * @author Suraj
 * 
 * Tree generation and actions such as adding new parent or child takes place here
 * Section Listeners for displaying relavent details of the selected student.
 */


package Student_Details;

import java.awt.GridLayout;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.TreeModelListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreePath;
import javax.swing.tree.TreeSelectionModel;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;

public class tree_generation extends JPanel
{


    protected DefaultMutableTreeNode rootNode;
    protected DefaultTreeModel treeModel;
    protected JTree tree;
    public  String studDetailsTxtbox_disp[] = new String[10];



    public tree_generation() 
    {
      super(new GridLayout(1,0));
        rootNode = new DefaultMutableTreeNode("Click for Student Details");
        treeModel = new DefaultTreeModel(rootNode);
    tree = new JTree(treeModel);
        tree.setEditable(true);
        tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
        tree.addTreeSelectionListener(new TreeSelectionListener() 
            {
           @Override
            public void valueChanged(TreeSelectionEvent e) 
           {
           studDetailsTxtbox_disp[0]= tree.getLastSelectedPathComponent().toString(); 
           Main_frame db = new Main_frame();
           db.dbaction(studDetailsTxtbox_disp[0]);
           }
        }); 
        tree.setShowsRootHandles(true);
        JScrollPane scrollPane = new JScrollPane(tree);
        add(scrollPane);
    }

    /** Add child to the currently selected node. */
    public DefaultMutableTreeNode addObject(Object child) 
    {
        DefaultMutableTreeNode parentNode = null;
        TreePath parentPath = tree.getSelectionPath();

        if (parentPath == null) {
            parentNode = rootNode;
        } 
        else 
        {
            parentNode = (DefaultMutableTreeNode)
                         (parentPath.getLastPathComponent());
        }

        return addObject(parentNode, child, true);
    }



    public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent,
                                            Object child) 
    {
        return addObject(parent, child, false);
    }




    public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent,
                                            Object child, 
                                            boolean shouldBeVisible) 
    {
        DefaultMutableTreeNode childNode = 
                new DefaultMutableTreeNode(child);

        if (parent == null) 
        {
            parent = rootNode;
        }

    //It is key to invoke this on the TreeModel
        treeModel.insertNodeInto(childNode, parent, 
                                 parent.getChildCount());

        //Make sure the user can see the new node.
        if (shouldBeVisible) 
        {
            tree.scrollPathToVisible(new TreePath(childNode.getPath()));
        }
        return childNode;
    }
      static void loadit()
      {


     tree_generation.treeModel.reload();
//i tried this too//
          //treePanel = new tree_generation();
      // populateTree(treePanel);
    }


    class MyTreeModelListener implements TreeModelListener {
        public void treeNodesChanged(TreeModelEvent e) {
            DefaultMutableTreeNode node;
            node = (DefaultMutableTreeNode)(e.getTreePath().getLastPathComponent());
   node.setUserObject("HELLO WORLD");
            /*
             * If the event lists children, then the changed
             * node is the child of the node we've already
             * gotten.  Otherwise, the changed node and the
             * specified node are the same.
             */

                int index = e.getChildIndices()[0];
                node = (DefaultMutableTreeNode)(node.getChildAt(index));

            System.out.println("The user has finished editing the node.");
            System.out.println("New value: " + node.getUserObject());
        }
        public void treeNodesInserted(TreeModelEvent e) {
        }
        public void treeNodesRemoved(TreeModelEvent e) {
        }
        @Override
        public void treeStructureChanged(TreeModelEvent e) 
        {
            System.out.println("tree sturct changed") ;
                 DefaultMutableTreeNode node;
            node = (DefaultMutableTreeNode)(e.getTreePath().getLastPathComponent());
   node.setUserObject("HELLO WORLD");
            tree.updateUI();
            e.getTreePath();
        }
    }
    }

查询 - 数据库名称:treedata2

create table student_details(student_name varchar(20),student_address varchar(30),student_school varchar(20));

insert into student_details values('suraj','mangalore','dps');
insert into student_details values('prassana','Bangalore lalbagh 23/16 2nd main road','dps');
insert into student_details values('deepika','Mangalore kadri park , 177b','dav');
insert into student_details values('sujith','delhi , rajinder nagar, d black','dav');
insert into student_details values('sanjay','bombay marina drive, 12/34','dav');
insert into student_details values('suresh','jaipur , lalbagh cjhowki','kv');
insert into student_details values('manu','surat, pune warior house','kv');
insert into student_details values('tarun','chennai, glof club','salwan');
insert into student_details values('vinay','haryana, indutrial area','hindu senior');
insert into student_details values('veeru','trivendrum, kottayam 12/77','canara')

Answer 1

好的，我想我发现了您的代码中有问题的地方，但您可能应该自己尝试并确认。

Class.forName("org.apache.derby.jdbc.ClientDriver");
connect_update = DriverManager.getConnection("jdbc:derby://localhost:1527/treedata2", "suraj", "suraj");
PreparedStatement updateQry = connect.prepareStatement("UPDATE student_details SET student_name='"+studDetailsTxtbxchange[0]+"',student_address='"+studDetailsTxtbxchange[1]+"',student_school='"+studDetailsTxtbxchange[2]+"' WHERE student_name='"+user_name+"' and student_address='"+user_add+"'and student_school='"+user_other+"'");
updateQry.executeUpdate();
JOptionPane.showMessageDialog(null,"Record Updated!","UPDATED",JOptionPane.OK_OPTION);
tree_generation.loadit();

在这段代码中，您确实更新了数据库，但没有更新树的模型。您正在调用静态方法 loadit() 但该方法不包含任何代码。为了工作，您可能应该刷新/重新加载您的 TreeModel。有不同的方法可以做到这一点。一种是直接发现 TreeNode 以使用新值刷新和更新它。另一种方法是重新创建您的整个 TreeModel(但如果您的树很大，这可能会很昂贵)。使用对象映射模型(例如 JPA/Hibernate)，您可以通过适当的 MVC 模式和模型通知更新值的 View 来获得更清晰的东西，但它需要额外的努力来设置。

就其值(value)而言，您应该考虑删除那些 static 关键字，因为它们不是必需的，也没有被适本地使用。只要有可能，您应该尽量避免使用该关键字(除非它与 final 结合使用来描述常量值)。

还有一点，尽量使用合适的LayoutManager的而不是使用绝对定位。使用适当的布局管理器可以让您的代码更易于维护，并且在不同平台/外观和感觉上更易于移植。