应用简单，一个框架中有两个面板
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。
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')
最佳答案
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。
关于java - 如何在 JTree 上显示动态更新？/如何刷新或重新加载 JTree？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11671242/