从JTextField中检索文本

Question

The concept of my code is that, it will initially retrieve distinct names from a column 'tname' of my access database table 'try'. It will add those items in a combobox. Once we select an item in the combo box, the data of the row containing tname as the selected item is retrieved and showed in textfields. Then I will make some changes to the text field content. After that, if I click 'Save' button, then all the data of the row containing tname as the selected combobox item must be updated with the new content in the textfields.

Everything goes fine, except the last one. When I click 'save' it considers only the previous text(the one intially retrieved from the database when we select combobox) and not the changes made to it. Kindly help me to diagnose the problem.

Thanks in advance.

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.table.*;
import java.util.Date;
import java.sql.*;
import java.text.*;

public class gut implements ActionListener
{
JComboBox ctn;
JTextField cm,exd,stk,cst,sup,snum,r;
String stn,scm,sexd,sst,scst,ssup,ssnum,sr,icm,iexd,istk,icst,isup,isnum,ir;
JLabel lt,lc,le,ls,lcs,lsp,lspn,lr;
JButton s;
JFrame gp=new JFrame();

public gut()
{
gp.setSize(500,500);
gp.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

gp.setLayout(null);

lt=new JLabel("Tablet Name",JLabel.RIGHT);
lc=new JLabel("Composition",JLabel.RIGHT);
le=new JLabel("Expiry Date (dd/mm/yyyy)",JLabel.RIGHT);
ls=new JLabel("Stock",JLabel.RIGHT);
lcs=new JLabel("Cost",JLabel.RIGHT);
lsp=new JLabel("Supplier",JLabel.RIGHT);
lspn=new JLabel("Supplier Number",JLabel.RIGHT);
lr=new JLabel("Rack",JLabel.RIGHT);

lt.setBounds(100,120,120,20);
lc.setBounds(100,140,120,20);
le.setBounds(60,160,160,20);
ls.setBounds(100,180,120,20);
lcs.setBounds(100,200,120,20);
lsp.setBounds(100,220,120,20);
lspn.setBounds(100,240,120,20);
lr.setBounds(100,260,120,20);

ctn=new JComboBox();
cm=new JTextField();
exd=new JTextField();
stk=new JTextField();
cst=new JTextField();
sup=new JTextField();
snum=new JTextField();
r=new JTextField();


ctn.setBounds(240,120,120,20);
cm.setBounds(240,140,120,20);
exd.setBounds(240,160,120,20);
stk.setBounds(240,180,120,20);
cst.setBounds(240,200,120,20);
sup.setBounds(240,220,120,20);
snum.setBounds(240,240,120,20);
r.setBounds(240,260,120,20);

try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection conn=DriverManager.getConnection("jdbc:odbc:vasantham","","");
Statement st=conn.createStatement();
ResultSet rs=st.executeQuery("select DISTINCT tname from try");

while(rs.next())
{
 ctn.addItem(rs.getString("tname"));
}

conn.close();
}
catch(Exception e)
{
}

gp.add(lt);gp.add(ctn);
gp.add(lc);gp.add(cm);
gp.add(le);gp.add(exd);
gp.add(ls);gp.add(stk);
gp.add(lcs);gp.add(cst);
gp.add(lsp);gp.add(sup);
gp.add(lspn);gp.add(snum);
gp.add(lr);gp.add(r);

ctn.addActionListener(this);
s=new JButton("Save");
s.setBounds(200,300,100,20);
gp.add(s);
s.addActionListener(this);




gp.setVisible(true);
}
public void actionPerformed(ActionEvent evt)
{
String act=evt.getActionCommand();

String scb=(String)ctn.getSelectedItem();
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection conn=DriverManager.getConnection("jdbc:odbc:vasantham","","");
Statement st=conn.createStatement();
ResultSet rs=st.executeQuery("select * from try where tname='"+scb+"'");
SimpleDateFormat formatter=new SimpleDateFormat("dd/MM/yyyy");

while(rs.next())
{
icm=rs.getString("composition");
iexd=formatter.format(rs.getDate("exdate"));
istk=Integer.toString(rs.getInt("stock"));
icst=rs.getString("cost");
isup=rs.getString("sup");
isnum=rs.getString("supnum");
ir=rs.getString("rack");
}

cm.setText(icm);
exd.setText(iexd);
stk.setText(istk);
cst.setText(icst);
sup.setText(isup);
snum.setText(isnum);
r.setText(ir);


conn.close();
}
catch(Exception e)
{
System.out.println(e);
}


if(act.equals("Save"))
{
scm=cm.getText();
sexd=exd.getText();
sst=stk.getText();
scst=cst.getText();
ssup=sup.getText();
ssnum=snum.getText();
sr=r.getText();
System.out.println(scm+","+sexd+","+sst+","+scst+","+ssup+","+ssnum+","+sr);
try
{

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection conn=DriverManager.getConnection("jdbc:odbc:vasantham","","");
PreparedStatement ps=conn.prepareStatement("UPDATE try set composition=?,exdate=?,stock=?,cost=?,sup=?,supnum=?,rack=? where 

tname=?");

ps.setString(1,scm);
ps.setString(2,sexd);
ps.setString(3,sst);
ps.setString(4,scst);
ps.setString(5,ssup);
ps.setString(6,ssnum);
ps.setString(7,sr);
ps.setString(8,scb);

ps.executeUpdate();

JOptionPane.showMessageDialog(null,"Your entry has been stored successfully!!!");

}
catch(Exception e)
{
JOptionPane.showMessageDialog(null,"Error!Try again!");
System.out.println(e);

}
}
}
public static void main(String[] args)
{
new gut();
}

}

Answer 1

Your actionPerformed() function retrieves the information from the database every time. If you press the Save button it will first retrieve the information and then save the information if the action command is "Save". This is why you always get the information that's currently in the database from getText() when pressing the Save button.

Make a different function / actionListener to execute when the Save button is pressed or take the part of the code that updates the text fields else where.

Try something like this instead:

JButton saveButton = new JButton( new AbstractAction("save") {
        @Override
        public void actionPerformed( ActionEvent e ) {
            // Save the info here or just call a function that will.
        }
    });

Answer 2

The problem is that every time you hit the "Save" button you are retrieving the information from the database over again, so, you overwrite the TextFields and then you read from the TexFields content. Try to take out this part:

 try {
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            Connection conn = DriverManager.getConnection

            ("jdbc:odbc:vasantham", "", "");
            Statement st = conn.createStatement();
            ResultSet rs = st.executeQuery("select * from try where tname='"
                    + scb + "'");
            SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");

            while (rs.next()) {
                icm = rs.getString("composition");
                iexd = formatter.format(rs.getDate("exdate"));
                istk = Integer.toString(rs.getInt("stock"));
                icst = rs.getString("cost");
                isup = rs.getString("sup");
                isnum = rs.getString("supnum");
                ir = rs.getString("rack");
            }

            cm.setText(icm);
            exd.setText(iexd);
            stk.setText(istk);
            cst.setText(icst);
            sup.setText(isup);
            snum.setText(isnum);
            r.setText(ir);

            conn.close();
        } catch (Exception e) {
            System.out.println(e);
        }

from the action performed method.

Answer 3

Every time your action event is fired, you read data from DB and write it into the textfields. You can change that text and it will be displayed correctly in your textfields. But when you click save, all your changes are overwritten with the DB values again.

So you have to separate the functionalities "read from DB" and "write changes".

edit: oops, too slow..

Answer 4

On top of what everybody else has already said, if you REALLY want to use a single action listener, you are going to need to work out which action has actually occurred.

You could check the source of the ActionEvent ( evt.getSource() ) or, more appropriately, you could assign a action command to each component using the action listener.

Check out JComboBox.setActionCommand(...) and JButton.setActionCommand(...)

After that, it's a simple case of checking the ActionEvent.getActionCommand() property to determine the correct action to take.