Data sharing problem

thinhare

In my program, there are two panels organized in CardLayout, panel 1 for user login, panel 2 for displaying user profile, and a singleton class is created for data sharing between these two panels.

Scenario can be, on panel 1, user type in username and password, click button "login", then in actionPerformed(ActionEvent e), username will be saved in singleton class String username = "somebody" and panel 2 will be made visible on the screen with the username in a JLabel.

My problem is, when I click the button, panel 2 shows up, but the username is lost, seems the change in actionPerformed() does not affect the singleton variable username. But if I put the change String username = "somebody" in constructor, the change takes place.

Any help will be appreciated!

CyberBlue

It may be changed elsewhere.

thinhare

thanks for reply. I've tested different ways of singleton, didn't work out though. the original code was long and a little messy. below is the simplified version which maintains the problem.

This is the main class of the program.

1. 
   
2. import javax.swing.*;
   
3. import java.awt.*;
   
4. 
   
5. public class AlbumSys extends JFrame {
   
6. 
   
7.     JPanel pnlCards = null;
   
8.     CardLayout layout = null;
   
9.    
   
10.     public AlbumSys ()
    
11.     {
    
12.         layout = new CardLayout();
    
13.         pnlCards = new JPanel(layout);
    
14.         pnlCards.add(new PanelAuthen(), "authentication");
    
15.         pnlCards.add(new PanelAlbumList(), "albumlist");
    
16.         getContentPane().add(pnlCards);
    
17.         setDefaultCloseOperation(EXIT_ON_CLOSE);
    
18.     }
    
19.    
    
20.     public void init()
    
21.     {
    
22.         setLocation(500, 400);
    
23.         pack();
    
24.         setVisible(true);
    
25.         
    
26.         while(true) {
    
27.             if (Repository.stageChanged) {
    
28.                 switch (Repository.currStage) {
    
29.                     case 0:
    
30.                         layout.show(pnlCards, "authentication");
    
31.                         break;
    
32.                     case 1:
    
33.                         layout.show(pnlCards, "albumlist");
    
34.                         break;
    
35.                     default:
    
36.                         layout.show(pnlCards, "authentication");
    
37.                 }
    
38.                 Repository.stageChanged = false;
    
39.             }
    
40.             
    
41.             try {
    
42.                 Thread.sleep(10);
    
43.             } catch (InterruptedException ie) {
    
44.                 ie.printStackTrace();
    
45.             }      
    
46.         }
    
47.     }
    
48.    
    
49.     public static void main(String[] args)
    
50.     {
    
51.         new AlbumSys().init();
    
52.     }
    
53. }
    
54. 
    

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This is the singleton class for data sharing between panels.

1. 
   
2. public class Repository {
   
3.    
   
4.     private final static Repository instance = new Repository();
   
5.     private Repository () {}
   
6.     public static Repository getInstance() { return instance; }
   
7.    
   
8.     public static int currStage = 0;
   
9.     public static Boolean stageChanged = false;
   
10.     public static String username = "Sad! It's not changed.";
    
11. }
    

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This is panel 1 for user login.

1. 
   
2. import javax.swing.*;
   
3. import java.awt.*;
   
4. import java.awt.event.*;
   
5. 
   
6. public class PanelAuthen extends JPanel implements ActionListener{
   
7.    
   
8.     public PanelAuthen()
   
9.     {
   
10.         Button btnSignIn = new Button("signin");
    
11.         btnSignIn.addActionListener(this);
    
12.         add(btnSignIn);
    
13.     }
    
14.    
    
15.     public void actionPerformed(ActionEvent e)
    
16.     {
    
17.         String cmd = e.getActionCommand();
    
18.         if (cmd.equals("signin")) {
    
19.             Repository.username = "Haha! It's been changed!";
    
20.             Repository.currStage = 1; // to switch to album list panel
    
21.             Repository.stageChanged = true;
    
22.         }
    
23.     }
    
24. }
    

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This is panel 2 for displaying user profile.

1. 
   
2. import javax.swing.*;
   
3. import java.awt.*;
   
4. import java.awt.event.*;
   
5. 
   
6. public class PanelAlbumList extends JPanel{
   
7. 
   
8.     public PanelAlbumList()
   
9.     {
   
10.         JLabel lblTitle = new JLabel(Repository.username);
    
11.         add(lblTitle);
    
12.     }
    
13. }
    

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[ 本帖最后由 thinhare 于 2008-3-17 20:40 编辑 ]

CyberBlue

The two panels are initialized and set the default value of their variables when the program start up. When you click the button their variables won't change.

So you must write some code that reload the text of the label. And add them to the action method of the button.

thinhare

that was exactly what I found out lately.  thanks!

microjuz

Good English, poor Java