how to auto update jcombobox?

[Punit Jain]

i apologies to making it confused...
i have removed all the unrelated code from my main class, here is formatted main class.
WelcomeScreen1.java

import javax.swing.*;
import javax.swing.border.EtchedBorder;
import javax.swing.border.MatteBorder;
import javax.swing.border.TitledBorder;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.SQLException;
public class WelcomeScreen1 extends JFrame{
JPanel mainPanel;
private BorderLayout bLayout;
CustomerLayout cl;
SearchByName searchByName;
JMenuBar menuBar;
JMenu file, admin, help, search;
JMenuItem register, searchName;
public static void main(String args[]) throws ClassNotFoundException, SQLException
{
new WelcomeScreen1();
}
WelcomeScreen1() throws ClassNotFoundException, SQLException
{
cl = new CustomerLayout();
searchByName = new SearchByName();
menuBar = new JMenuBar();
mainPanel = new JPanel();
bLayout = new BorderLayout(5,5);
mainPanel.setLayout(bLayout);
/*********** MenuBar starts here ***********/
file = new JMenu("General");
admin = new JMenu("Admin");
register = new JMenuItem("Register");
search = new JMenu("Search");
searchName = new JMenuItem("By Name");
admin.add(search);
search.add(searchName).addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
mainPanel.add(searchByName.panel, BorderLayout.CENTER);
cl.panel.hide();
searchByName.panel.show();
mainPanel.revalidate();
mainPanel.repaint();
}
});
file.add(register).addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
mainPanel.add(cl.panel, BorderLayout.CENTER);
searchByName.panel.hide();
cl.panel.show();
mainPanel.revalidate();
mainPanel.repaint();
}
});
menuBar.add(file);
menuBar.add(admin);
this.add(menuBar);
this.setTitle("Poona College TC Software");
setJMenuBar(menuBar);
/*********** MenuBar Ends Here ***********/
mainPanel.setOpaque(true);
this.add(mainPanel);
this.setSize(1280,750);
this.setExtendedState(Frame.MAXIMIZED_BOTH);
this.setVisible(true);
this.setResizable(false);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

[Michael Dunn]

I can put all this together now, and, *very* seriously a lot of it is garbage, and should be thrown out.

hide/show? that type of coding disappeared in the last century - if you must toggle between screens,
use a CardLayout.

I've posted several times to get rid of the search function, and to add it later when you get the original
problem working.

So, unless you're prepared to post an opening screen with a textfield/comboBox/button, where the
comboBox is loaded from a database (include the db code, I can easily simulate an arraylist for it),
and the button, when clicked, will add whatever is in the textfield to the database, then subsequently
refreshing the comboBox with the newly added data, I can do no more - someone else may come along
and assist.

[Punit Jain]

 

hide/show? that type of coding disappeared in the last century - if you must toggle between screens,
use a CardLayout.

i was not aware to that, i will replace that code, with cardlayout.

I've posted several times to get rid of the search function, and to add it later when you get the original
problem working.

okay, below is the display and display1 class, here combobox is added from database.

Display1.java

import java.sql.SQLException;
import java.util.ArrayList;
import javax.swing.*;
public class Display1 {
JPanel panel1;
JComboBox studentNames = new JComboBox();
DefaultComboBoxModel dcm = new DefaultComboBoxModel();
LoadStudents ls = new LoadStudents();
SaveStudent ss = new SaveStudent();
public void Display() throws SQLException {
ls.loadStudents1(studentNames);
panel1 = new JPanel();
panel1.add(studentNames);
}
}

Display.java

public class Display{
JPanel panel;
JTextField tf;
ArrayList<String> database = new ArrayList<String>();
JButton btn;
JFrame frame;
JComboBox studentNames = new JComboBox();
DefaultComboBoxModel dcm = new DefaultComboBoxModel();
LoadStudents ls = new LoadStudents();
SaveStudent ss = new SaveStudent();
Display1 d1 = new Display1();
public Display() {
btn = new JButton("Add Student");
tf = new JTextField(15);
panel = new JPanel();
panel.add(tf);
panel.add(btn);
frame = new JFrame();
frame.add(panel);
frame.setVisible(true);
frame.setSize(200,100);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
btn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
try {
String values = tf.getText();
ss.saveStudent(values);
} catch (SQLException e) {
e.printStackTrace();
}
panel.hide();
panel.repaint();
panel.revalidate();
try {
d1.Display();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
frame.add(d1.panel1);
}
});
}
public static void main(String args[]){
new Display();
}
}

rest of the classes, loadStudent, saveStudent, Db are same.

[Michael Dunn]

it all works fine here.
I wrapped all ther classes together, so they could 'see' the simulated database.
you just need to put back the db code and it should work the same way.

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.*;
class Display
{
CardLayout cl = new CardLayout();//added
JPanel cardPanel = new JPanel(cl);//added
JPanel panel = new JPanel();
JTextField tf = new JTextField(15);
ArrayList<String> resultSetList = new ArrayList<String>();//simulate resultSet from db query
JButton btn = new JButton("Add Student");
JFrame frame = new JFrame();
JComboBox studentNames = new JComboBox();
DefaultComboBoxModel dcm = new DefaultComboBoxModel();
LoadStudents ls = new LoadStudents();
SaveStudent ss = new SaveStudent();
Display1 d1 = new Display1();
public Display()
{
cardPanel.add(panel,"display");//added
cardPanel.add(d1.panel1,"display1");//added
panel.add(tf);
panel.add(btn);
//frame.add(panel);
frame.add(cardPanel);
frame.setVisible(true);
frame.setSize(200,100);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
btn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
String values = tf.getText();
ss.saveStudent(values);
tf.setText("");
d1.update();
cl.show(cardPanel,"display1");
}
});
}
public static void main(String args[]){new Display();}
class Display1
{
JPanel panel1 = new JPanel();
JComboBox studentNames = new JComboBox();
DefaultComboBoxModel dcm = new DefaultComboBoxModel();
LoadStudents ls = new LoadStudents();
SaveStudent ss = new SaveStudent();
//public void Display() {
public Display1() //now a constructor
{
ls.loadStudents1(studentNames);
panel1.add(studentNames);
JButton btn = new JButton("<<Back");
panel1.add(btn);
btn.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae){
cl.show(cardPanel,"display");
tf.requestFocusInWindow();
}
});
}
public void update()//added
{
ls.loadStudents1(studentNames);
}
}
class LoadStudents
{
ArrayList><String> database1;
DefaultComboBoxModel model;
public void loadStudents1(JComboBox cbo)
{
//ResultSet ress;
ArrayList ress;
Db db = new Db();
model = new DefaultComboBoxModel();
ress = db.NameValues();
ListIterator iter = ress.listIterator();
//while(ress.next()){
//model.addElement(ress.getString("names"));
//}
while (iter.hasNext())
{
model.addElement(iter.next());
}
cbo.setModel(model);
}
}
class SaveStudent
{
public void saveStudent(String values)
{
Db db = new Db();
db.Insert1(values);
}
}
class Db
{
//public ResultSet NameValues() throws SQLException{
public ArrayList<String> NameValues(){
//Statement ps;
//ResultSet res;
//System.out.println("Inside db");
//String query = "SELECT names FROM studentregistration";
// DbConnection dbconn = new DbConnection();
//Connection conn = dbconn.dbConn();
//ps = conn.createStatement();
//res = ps.executeQuery(query);
//return res;
return resultSetList;
}
public void Insert1(String nm)
{
//try{
//PreparedStatement st;
//String query = "INSERT into studentregistration (names) VALUES (?)";
//DbConnection dbconn = new DbConnection();
//Connection conn = dbconn.dbConn();
//st = conn.prepareStatement(query);
//st.setString(1,nm);
//int rr = st.executeUpdate();
//System.out.println(rr);
//}catch(Exception e){e.printStackTrace();}
resultSetList.add(nm);
}
}
}

[Punit Jain]

michael,
with arraylist code is works fine here, but i just added the db part, and again the same problem, nothing i did i only added the db part, i mean just uncomment that, and commented the arraylist.
again i have to restart my application to see the last inserted value, not getting updated.
here is the code with db:-

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.*;
class Display
{
CardLayout cl = new CardLayout();//added
JPanel cardPanel = new JPanel(cl);//added
JPanel panel = new JPanel();
JTextField tf = new JTextField(15);
//ArrayList<String> resultSetList = new ArrayList<String>();//simulate resultSet from db query
JButton btn = new JButton("Add Student");
JFrame frame = new JFrame();
JComboBox studentNames = new JComboBox();
DefaultComboBoxModel dcm = new DefaultComboBoxModel();
LoadStudents ls = new LoadStudents();
SaveStudent ss = new SaveStudent();
Display1 d1 ;
public Display()throws SQLException
{
d1 = new Display1();
cardPanel.add(panel,"display");//added
cardPanel.add(d1.panel1,"display1");//added
panel.add(tf);
panel.add(btn);
//frame.add(panel);
frame.add(cardPanel);
frame.setVisible(true);
frame.setSize(200,100);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
btn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
String values = tf.getText();
try {
ss.saveStudent(values);
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
tf.setText("");
try {
d1.update();
} catch (SQLException e) {
e.printStackTrace();
}
cl.show(cardPanel,"display1");
}
});
}
public static void main(String args[]) throws SQLException{new Display();}
class Display1
{
JPanel panel1 = new JPanel();
JComboBox studentNames = new JComboBox();
DefaultComboBoxModel dcm = new DefaultComboBoxModel();
LoadStudents ls = new LoadStudents();
SaveStudent ss = new SaveStudent();
//public void Display() {
public Display1() throws SQLException //now a constructor
{
ls.loadStudents1(studentNames);
panel1.add(studentNames);
JButton btn = new JButton("<<Back");
panel1.add(btn);
btn.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae){
cl.show(cardPanel,"display");
tf.requestFocusInWindow();
}
});
}
public void update() throws SQLException//added
{
ls.loadStudents1(studentNames);
}
}
class LoadStudents
{
//ArrayList<String> database1;
DefaultComboBoxModel model;
public void loadStudents1(JComboBox cbo) throws SQLException
{
ResultSet ress;
//ArrayList ress;
Db db = new Db();
model = new DefaultComboBoxModel();
ress = db.NameValues();
//ListIterator iter = ress.listIterator();
while(ress.next()){
model.addElement(ress.getString("names"));
}
/*while (iter.hasNext())
{
model.addElement(iter.next());
}*/
cbo.setModel(model);
}
}
class SaveStudent
{
public void saveStudent(String values) throws SQLException
{
Db db = new Db();
db.Insert1(values);
}
}
class Db
{
public ResultSet NameValues() throws SQLException{
//public ArrayList<String> NameValues(){
Statement ps;
ResultSet res;
System.out.println("Inside db");
String query = "SELECT names FROM studentregistration";
DbConnection dbconn = new DbConnection();
Connection conn = dbconn.dbConn();
ps = conn.createStatement();
res = ps.executeQuery(query);
return res;
//return resultSetList;
}
public void Insert1(String nm)
{
try{
PreparedStatement st;
String query = "INSERT into studentregistration (names) VALUES (?)";
DbConnection dbconn = new DbConnection();
Connection conn = dbconn.dbConn();
st = conn.prepareStatement(query);
st.setString(1,nm);
int rr = st.executeUpdate();
System.out.println(rr);
}catch(Exception e){e.printStackTrace();}
//resultSetList.add(nm);
}
}
}

[Michael Dunn]

you'll have to put in a bunch of System.out.println's (one at a time) starting at
line 49 d1.update()
to see where the program goes i.e. if the message is printed, move the println
to the next section. Eventually you should find where the message is not printed
so you can check that bit of code.

the code looks OK.
the only db stuff I've done was ages ago, in another language, where you had to
close the connection. That may be the same in java, don't know.

[Punit Jain]

instead of loading the resultset into combobox, if i load the arraylist, all works fine.
values are going into db.
but when i load resultset, the problem comes.

[Punit Jain]

well, i tried something, and it's worked, only one problem is in this approach.
what i did is:
in the nameValues(), instead of returning resultset, i added resultset to arraylist, and then i am returning arraylist, it's worked, but values in combobox are coming multiple times.
i mean the value which i entered last in coming once, but the earlier ones getting increased, might be some problem in loop..?
here is the method:

//public ResultSet NameValues() throws SQLException{
public ArrayList<String> NameValues()throws SQLException{
Statement ps;
ResultSet res;
System.out.println("Inside db");
String query = "SELECT names FROM studentregistration";
DbConnection dbconn = new DbConnection();
Connection conn = dbconn.dbConn();
ps = conn.createStatement();
res = ps.executeQuery(query);
//return res; //removed this---------------->
while(res.next()){ //added this------------------>
resultSetList.add(res.getString("names"));//added this------------------>
}
return resultSetList;
}

calling in the same way..

public void loadStudents1(JComboBox cbo) throws SQLException
{
//ResultSet ress;
ArrayList ress;
Db db = new Db();
model = new DefaultComboBoxModel();
ress = db.NameValues();
ListIterator iter = ress.listIterator();
//while(ress.next()){
//model.addElement(ress.getString("names"));
//}
while (iter.hasNext())
{
model.addElement(iter.next());
}
cbo.setModel(model);
}

[Michael Dunn]

everything looks OK, and it must work OK, because it loads the newly saved data
if you close the app then reopen it.

the problem is when update() is called, so you'll just have to go through those steps
I posted earlier. you could also printout the resultSet size to see if there's any difference
between when the app opens, and when something is saved.

[Punit Jain]

finally done......
the problem was here:

public Display1() throws SQLException //now a constructor
{
System.out.println("3.> Inside Display Constructor");
//ls.loadStudents1(studentNames); //This should not be called in the constructor--------->
panel1.add(studentNames);
JButton btn = new JButton("<<Back");
panel1.add(btn);
btn.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae){
System.out.println("4.> Inside Back Button ActionListener");
cl.show(cardPanel,"display");
tf.requestFocusInWindow();
}
});
}

thank you thank you thank you very much michael..
your help is very much appreciable..
Thank you

[Michael Dunn]

> finally done.....

well done, I knew you'd get there in the end - mostly just a matter of putting things together in the right order.

[Punit Jain]

 

well done, I knew you'd get there in the end - mostly just a matter of putting things together in the right order.

yes, and also because of your help..
so thanks agaiin michael..