creating a new JPanel from another JPanel "choice" button

[mike ryan]

Hi,

I am have a JPanel with 3 JButtons for options to pick, and also a two other buttons to either quit or to do an equasion.


this is the 3 buttons as choices

 private JPanel panelChoices (){
            
            
            JPanel tempPanel = new JPanel();
            
            dichte = new JButton("Dichte");
            dichte.setActionCommand("dichte");          
            
            volumen = new JButton("Volumen");
            volumen.setActionCommand("volumen");
            
            masse = new JButton("Masse");
            masse.setActionCommand("masse");
            
            tempPanel.add(dichte);
            tempPanel.add(volumen);
            tempPanel.add(masse);
            
            tempPanel.setLayout(new GridLayout(0,1,5,5));
            
            tempPanel.setBorder(new TitledBorder("Operation"));
            
            MeinListener listener = new MeinListener();
            
            dichte.addActionListener(listener);
            volumen.addActionListener(listener);
            masse.addActionListener(listener);
            
                
            return tempPanel;
        }

and i would like to create a new JPanel when one of the buttons is clicked.
the JPanel for the first JButton that can be clicked is below.

JPanel panelDichteRechnen(){
        
            JPanel tempPanel = new JPanel();
        
            eingabe1 = new JTextField(10);
        
            eingabe2 = new JTextField(10);
        
            ausgabe = new JLabel("");
        
            tempPanel.setLayout(new GridLayout(0,2,10,10));
        
            tempPanel.add(new JLabel("Masse:"));
            
            tempPanel.add(eingabe1);
        
            tempPanel.add(new JLabel("Volumen:"));
        
            tempPanel.add(eingabe2);
        
            tempPanel.add(new JLabel("Ergebnis: "));
        
            tempPanel.add(ausgabe);
        
            tempPanel.setBorder(new TitledBorder("Ein- und Ausgabe"));
        
            return tempPanel;
        }
        

and i am trying to get it to start with this

 class MeinListener extends JPanel implements ActionListener {
            @Override
            public void actionPerformed(ActionEvent e){
                
                if(e.getActionCommand().equals("ende"))
                    
                    System.exit(0);
                
                if(e.getActionCommand().equals("rechnen"))
                    
                    ausgabe.setText(berechnen());
                
                if(e.getActionCommand().equals("dichte")){///////////here
                                     
                  add(panelDichteRechnen());
                   
                }
                   
                
            }

I am just learning GUI's so i am sure there are some mistakes here but i am just trying what i think should work ;) Right now i don't get an error Message but no new JPanel comes up either.


Thanks
Mike

[Rob Spoor]

Whenever you modify the GUI hierarchy tree while the GUI is already shown you need to revalidate() and repaint() the container you added a component to or removed a component from.

[mike ryan]

Thanks Rob! I will give that a try in a few and see what happens!!

[mike ryan]

Hi again,

So, I have been trying to remove the JPanel i added when another button is clicked , so it removes the current on and adds the new one. Not sure i am doing it properly?
the entire code is below ,maybe someone can steer me in the right direction?

import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.TitledBorder;


@SuppressWarnings("serial")
public class FormulaDoctorGUI extends JFrame{
    
    private JTextField eingabe1, eingabe2;
    
    
    private JButton schaltflaecheBerechnen, schaltflaecheBeenden, dichte, masse, volumen;
    
    private JLabel ausgabe;

    public JPanel JPanel;
    
         JPanel panelDichteRechnen(){
        
            JPanel dichtePanel = new JPanel();
        
            eingabe1 = new JTextField(10);
        
            eingabe2 = new JTextField(10);
        
            ausgabe = new JLabel("");
        
            dichtePanel.setLayout(new GridLayout(0,2,10,10));
        
            dichtePanel.add(new JLabel("Masse:"));
            
            dichtePanel.add(eingabe1);
        
            dichtePanel.add(new JLabel("Volumen:"));
        
            dichtePanel.add(eingabe2);
        
            dichtePanel.add(new JLabel("Ergebnis: "));
        
            dichtePanel.add(ausgabe);
        
            dichtePanel.setBorder(new TitledBorder("Dichte rechnen"));
            
            add(dichtePanel);
            
            pack();
            
            setVisible(true);
            
                 
            return dichtePanel;
        }
         
         JPanel panelMasseRechnen(){
             
             JPanel massePanel = new JPanel();
         
             eingabe1 = new JTextField(10);
         
             eingabe2 = new JTextField(10);
         
             ausgabe = new JLabel("");
         
             massePanel.setLayout(new GridLayout(0,2,10,10));
         
             massePanel.add(new JLabel("dichte:"));
             
             massePanel.add(eingabe1);
         
             massePanel.add(new JLabel("Volumen:"));
         
             massePanel.add(eingabe2);
         
             massePanel.add(new JLabel("Ergebnis: "));
         
             massePanel.add(ausgabe);
         
             massePanel.setBorder(new TitledBorder("Masse rechnen"));
             
             add(massePanel);
             
             pack();
             
             setVisible(true);
             
                  
             return massePanel;
         }
        
        private JPanel panelChoices (){
            
            
            JPanel tempPanel = new JPanel();
            
            dichte = new JButton("Dichte");
            dichte.setActionCommand("dichte");          
            
            volumen = new JButton("Volumen");
            volumen.setActionCommand("volumen");
            
            masse = new JButton("Masse");
            masse.setActionCommand("masse");
            
            tempPanel.add(dichte);
            tempPanel.add(volumen);
            tempPanel.add(masse);
            
            tempPanel.setLayout(new GridLayout(0,1,5,5));
            
            tempPanel.setBorder(new TitledBorder("Operation"));
            
            MeinListener listener = new MeinListener();
            
            dichte.addActionListener(listener);
            volumen.addActionListener(listener);
            masse.addActionListener(listener);
            
                
            return tempPanel;
        }
        
       
        
        private JPanel panelButtonsErzeugen(){
            
            JPanel tempPanel = new JPanel();
            
            schaltflaecheBeenden = new JButton("Beenden");
            
            schaltflaecheBeenden.setActionCommand("ende");
            
            schaltflaecheBerechnen = new JButton("Berechnen");
            
            schaltflaecheBerechnen.setActionCommand("rechnen");
            
            // zwischenpanel für die schaltflaechen linksbundig
            
            tempPanel.setLayout(new FlowLayout(FlowLayout.LEFT,20,10));
            
            tempPanel.add(schaltflaecheBeenden);
            
            tempPanel.add(schaltflaecheBerechnen);
            
              //schaltflaeche mit dem listener verbinden
            
              MeinListener listener = new MeinListener();
            
              schaltflaecheBeenden.addActionListener(listener);
            
              schaltflaecheBerechnen.addActionListener(listener);
            
            return tempPanel;
            
        }
        
        public FormulaDoctorGUI (String titel){          
            
            super(titel);                
            
            setLayout(new GridLayout() );
            
            add(panelChoices());
            add(panelButtonsErzeugen());
                  
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            
            setResizable(false);
            
            pack();
            setLocationByPlatform(true);
            setVisible(true);          
           
            }     

        private String berechnen(){
                       
            double zahl1,zahl2, ergebnis = 0;            
            
            boolean fehlerFlag = true;
            
            zahl1 = Double.parseDouble(eingabe1.getText());
            
            zahl2 = Double.parseDouble(eingabe2.getText());
            
          if(dichte.isSelected()== true){
          
              if(zahl2 !=0)
                  
                  ergebnis = zahl1 / zahl2;
              else
                  fehlerFlag = false;
          }
                  if(fehlerFlag = true)
                      
                      return (Double.toString(ergebnis));
                  else
                      return("Nicht Definiert");      
            
        }
                    
        
        class MeinListener extends JPanel implements ActionListener {
            @Override
            public void actionPerformed(ActionEvent e){
                
                if(e.getActionCommand().equals("ende"))
                    
                    System.exit(0);
                
                if(e.getActionCommand().equals("rechnen"))
                    
                    ausgabe.setText(berechnen());
                
                if(e.getActionCommand().equals("dichte")){
                  System.out.println("i have been pressed DEFINATELY!!!");
                 JPanel dichtePanel =  panelDichteRechnen();
                                
                }                
                 
                   if(e.getActionCommand().equals("masse")){
                      remove(add(panelDichteRechnen()));
                     this.revalidate();
                      this.repaint();
                       
                      JPanel massePanel = panelMasseRechnen();
                                                     
                  }
                   
                }
                   
                
            }
        }
        

Maybe I am adding the new JPanel in the wrong place or improperly?


Thanks
Mike

[Paul Clapham]

There's a lot of things there which are, let's say, confusing.

For example, at line 234 you create a MasseRechnen panel and then do nothing with it.

Likewise at line 225 you create a DichteRechnen panel and then do nothing with it. Both those lines could be thrown out -- unless creating the panels has some side effect, which wouldn't be a good idea.

And at lines 231 and 232 you revalidate and repaint... what, exactly? The code is inside a JPanel (declared at line 211), so you're revalidating and repainting that. Which is kind of pointless, because you don't have a displayed instance of MeinListener anyway. I can't understand why you have a listener which is a JPanel, especially one which is never actually used as a JPanel. You actually want to revalidate and repaint the main JFrame.

And you have one those awful listeners (which were popular in tutorials about ten years ago) which listens for a whole lot of different events and then has a whole series of if-statements which do completely different things based on which event they heard. It's better to have one listener for each different event. (Basic programming rule: an object should have one responsibility.) I would rewrite the code which assigns listeners to buttons so that it assigns a separate anonymous inner class (which implements ActionListener) for each button (or whatever) which will generate events.

You can probably tell I didn't read all of your code. There was a lot of it, that's why. You might consider stepping back for a bit. You're having a problem with adding new components? Then write a much smaller program which only does that and nothing else. Make that work, and then implement the working technique into your big program. That would have two advantages: less code to distract you, and less code for other people to wade through.

By the way I've never written a Swing program which tries to add or remove components. (And based on what I've seen on forums, I'm glad I haven't tried that.) What I do is to put all of the components into the GUI when I initialize it, and set them to be visible or invisible as required. No nasty revalidating or repainting necessary.

[mike ryan]

Hi Paul,

First off thanks for the good advice , i think my books are a little outdated and they show using listeners in this fashion that is why i used the same (it is the only way i have learned so far, and i really just started to learn about GUI's).

i will go through the problems you mentioned and try to explain.

line 234 actually creates the new panel and it works to add the new panel.

line 225 creates the new panelDichteRechnen() panel which also works, and i can write in the text fields and get the answer as well, although that formula isn't working correctly at the moment either but i am trying to get the panels right first.

line 231 and 232 i am trying to remove the panelDichteRechnen() panel that is there and then add the panel on line 234, but so far it just add the new panel on the right beside the other one i first created.

And yes i get your point about someone having to look through all the code, but i figured only the snippets wouldn't show exactly what i am trying to do.

the adding a JPanel seems to work fine, i just can't get rid of the one before adding the new one, it just continues to add new ones to the right. If noone else has an idea how to do this then i will have to consider learning a new way such as you wrote with setVisible(true or false);

Thank you for your time!!
Mike

[Darryl Burke]

I have been trying to remove the JPanel i added when another button is clicked , so it removes the current on and adds the new one.

Ever heard of CardLayout?

[mike ryan]

Darryl Burke wrote:

I have been trying to remove the JPanel i added when another button is clicked , so it removes the current on and adds the new one.

Ever heard of CardLayout?

I have now ;) i will check it out!

Thanks
Mike

[mike ryan]

Hi again,

So i have redone this GUI with the CardLayout, it is working as far as changing the panels for the correct choice, but the calculation done in the compute() method always returns zero? I thought i had
it set up correctly, but something must be incorrect! Any help would be appreciated.

here is the code:

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;




public class FormulaDoctor implements ItemListener {


    JPanel cards;
    JPanel currentPanel;   
    JTextField eingabe1,eingabe2;
    JButton end, compute;  
    JLabel answer;
    final static String DICHTE = "Dichte";
    final static String MASSE = "Masse";
    final static String VOLUME = "Volume";  

    public void addComponentToPane (Container pane) {  

        JPanel comboBoxPane = new JPanel(); //use FlowLayout
        String comboBoxItems[] = {  DICHTE, MASSE, VOLUME };
        JComboBox cb = new JComboBox(comboBoxItems);
        cb.setEditable(true);
        cb.addItemListener(this);

        comboBoxPane.add(cb);   

        //Create the "cards"  

        JPanel dichte = new JPanel();
        dichte.setLayout(new GridLayout(0,2,2,2));

        MyListener listener = new MyListener();

        eingabe1 = new JTextField(10);  
        eingabe2 = new JTextField(10);
        answer = new JLabel("");
        end = new JButton("end");
        end.setActionCommand("End");
        end.addActionListener(listener);
        compute = new JButton("compute");
        compute.setActionCommand("Compute");
        compute.addActionListener(listener);

        dichte.add(new JLabel("masse:")); 
        dichte.add((eingabe1));
        dichte.add(new JLabel("volume:"));   
        dichte.add(eingabe2);
        dichte.add(end);    
        dichte.add(compute);
        dichte.add(new JLabel("answer"));
        dichte.add(answer);

        // add masse panel

        JPanel masse = new JPanel();
        masse.setLayout(new GridLayout(0,2));
        masse.add(new JLabel("volume"));
        masse.add(new JTextField(10));
        masse.add(new JLabel("dichte"));
        masse.add(new JTextField(10));
        masse.add(new JButton("end"));
        masse.add(new JButton("compute"));
        masse.add(new JLabel("answer"));

        // add volume panel

        JPanel volume = new JPanel();
        volume.setLayout(new GridLayout(0,2));
        volume.add(new JLabel("masse"));
        volume.add(new JTextField(10));
        volume.add(new JLabel("dichte"));
        volume.add(new JTextField(10));
        volume.add(new JButton("end"));
        volume.add(new JButton("compute"));
        volume.add(new JLabel("answer"));

        //Create the panel that contains the "cards".
        cards = new JPanel(new CardLayout());

        cards.add(dichte, DICHTE);
        cards.add(masse, MASSE);
        cards.add(volume, VOLUME);

        pane.add(comboBoxPane, BorderLayout.PAGE_START);
        pane.add(cards, BorderLayout.CENTER);

    }

    @SuppressWarnings("serial")
    class MyListener extends JPanel implements ActionListener {        

        @Override  
        public void actionPerformed(ActionEvent e){  

            if(e.getActionCommand().equals("End"))  

                System.exit(0);  

            if(e.getActionCommand().equals("Compute"))

                answer.setText(compute());      


        }



    }
    public void itemStateChanged(ItemEvent evt) {
        CardLayout cl = (CardLayout)(cards.getLayout());
        cl.show(cards, (String)evt.getItem());
    }
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("Formula Doctor");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        FormulaDoctor FD = new FormulaDoctor();
        FD.addComponentToPane(frame.getContentPane());

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    private String compute(){

        double firstNumber,secondNumber,answer = 0;


        //boolean mistakeFlage = false;

        firstNumber = Double.parseDouble(eingabe1.getText());

        secondNumber = Double.parseDouble(eingabe2.getText());

        if(cards.equals(DICHTE)&& secondNumber!=0){

            answer = firstNumber / secondNumber;

        }

        else if(cards.equals(MASSE)){

            answer = firstNumber * secondNumber;

        }

        else if(cards.equals(VOLUME)&& secondNumber !=0){

            answer = firstNumber / secondNumber;


        }
        return Double.toString(answer);
    }

    public static void main(String[] args) {
        /* Use an appropriate Look and Feel */
        try {
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
            UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
        } catch (UnsupportedLookAndFeelException ex) {
            ex.printStackTrace();
        } catch (IllegalAccessException ex) {
            ex.printStackTrace();
        } catch (InstantiationException ex) {
            ex.printStackTrace();
        } catch (ClassNotFoundException ex) {
            ex.printStackTrace();
        }
        /* Turn off metal's use of bold fonts */
        UIManager.put("swing.boldMetal", Boolean.FALSE);

        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

I only have the first card "dichte" set up properly as this is an "work in progress" and i am trying to get the first one working properly, then i will fix the other 2 cards to match...

Thanks Mike

[mike ryan]

ok i have got it working but in a strange way , maybe i am missing something or not thinking properly

 private String compute(){

        double firstNumber,secondNumber,computed = 0;
        boolean mistakeFlag = false;

        firstNumber = Double.parseDouble(eingabe1.getText());
       //System.out.println(firstNumber);

        secondNumber = Double.parseDouble(eingabe2.getText());
        //System.out.println(secondNumber);       

        if(cards.equals(DICHTE)&& secondNumber!=0)
             System.out.println(computed);// this part works properly when i have the System.out.println(computed);??????
                                          // if i comment it out then it doesn't work????? 
             computed = firstNumber / secondNumber;
                               
        if(cards.equals(MASSE))
           //  System.out.println(computed);
            computed = firstNumber * secondNumber;
           
        if(cards.equals(VOLUME)&& secondNumber !=0)

            computed = firstNumber / secondNumber;  
           
       
      
        return Double.toString(computed);
        }

I commented on the current poroblem/ strangeness!! why is that so?

thanks
Mike

[mike ryan]

ok i have been trying this for a long time, and it seems as though i am not finding the current card. and getting an empty string .

can someone tell me how to figure out which card is the current one showing?


Thanks
Mike

[Rob Spoor]

Go through the panel's child components and check the visible flag.

[mike ryan]

Hi Rob,

Thanks for the quick answer, but i am not sure how to do that? could you elaborate a little more please?

I thought to try if(DICHTE.isVisible()) but that doesn't work.

thanks
Mike

[Rob Spoor]

If dichte (lower case, DICHTE is a String) is the currently visible panel then its isVisible() method should return true. If not then it should return false. That's how CardLayout works, it makes all children except the current one invisible.

[mike ryan]

Thanks again Rob!! , I am still new at this so will try to grasp what you wrote here and use it properly.


Mike

[mike ryan]

Hi Rob,

Still haven't figured it out.... I am not sure exactly what you mean?

i tried also something like this

public JPanel getCurrentCard()
    {
        JPanel currentCard = null;

        for (Component comp : cards.getComponents() ) {
            if (comp.isShowing() == true) {
                currentCard = (JPanel)comp;
                System.out.println("hi i am current card "+comp);
            }
        }
        System.out.println("what is this doing? "+cards.getComponents().toString());

        return currentCard;
    }

but still doesn't seem to do the trick? still getting a null pointer exception.

Thanks
Mike

[Rob Spoor]

Why are you using isShowing() when I suggested isVisible()?

Check out the following little example:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class Test
{
    public static void main(String[] args) throws Exception
    {
        final JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final CardLayout layout = new CardLayout();
        final JPanel parent = new JPanel(layout);
        for (int i = 0; i < 5; i++)
        {
            JPanel panel = new JPanel();
            panel.setPreferredSize(new Dimension(100, 100));
            panel.setName(String.valueOf(i));
            panel.add(new JLabel(panel.getName()));
            parent.add(panel, panel.getName());
        }
        frame.add(parent, BorderLayout.CENTER);
        frame.add(new JButton(new AbstractAction("Click")
        {
            public void actionPerformed(ActionEvent e)
            {
                for (Component c: parent.getComponents())
                {
                    if (c.isVisible())
                    {
                        System.out.println(c.getName());
                    }
                }
                layout.next(parent);
            }
        }), BorderLayout.SOUTH);
        frame.pack();
        frame.setVisible(true);
    }
}

However, isShowing() should also work, at least if the frame is visible at the time.

[mike ryan]

Hi Rob!

Thanks again, and the sample code is very nice;). I will see if i can incorperate that in my code!!

PS: The reason i had isShowing(); there is because i was trying allot of different things i found through Google before i had to
break down and ask here again

Since i started learning Java about 7 Months ago or so i have had a couple of things that just had me stumped , and this is one of those things!!
eventually i get it in the end most of the time;) i will let you know how it works out (or not)..

Thanks for your help
Mike

[mike ryan]

Hi,

So i have been working on this again and i still don't have it figured out completely.

i have this to find the current Component (JPanel)

 public JPanel getCurrentPanel(){
            
        for(Component currentPanel :cards.getComponents()){
                     
            if(currentPanel != null){//isShowing()){  // ******** TEST WITH NULL TO SEE ALL COMPONENTS *********
                
              System.out.println(cards.getComponents().hashCode());
              
              
            }
            System.out.println(currentPanel.isVisible());
           }
        return currentPanel;
              
    }

i have this to check which panel is showing

 @SuppressWarnings("serial")
    class MyListener extends JPanel implements ActionListener {          

        @Override  
        public void actionPerformed(ActionEvent e){              
            
            if(e.getActionCommand().equals("End"))  

                System.exit(0);  

            if(e.getActionCommand().equals("Compute"))//&& currentPanel.equals(???????))// what do i put here to get the current panel??
             
              System.out.println("i am the dichte panel");
            
            getCurrentPanel();           

        }
        
    }

and with it set up like this to test it prints out

i am the dichte panel
1943692956
true
126273328
false
561980460
false

So i can see that one isVisible() is true and the other 2 false and i see the hash codes from all three BUT, I don't know what to put in if (currentPanel.equals(WHAT TO PUT HERE TO CHECK???)) only choices Eclipse shows
me is DICHTE? but using that doesn't work as i already knew.

been trying it over and over but can't get it worked out?

EDIT!!! OK i geuss i will need to Iterate? but not exactly sure how to do it?

Mike

[mike ryan]

bump..

[Rob Spoor]

Give each panel a name when you create them, using setName(DICHTE), setName(MASSE), etc.
Get the current panel using a method based on that method (you need to return the actual visible panel).
Make sure it isn't null (using an if-statement).
Call getName() on the returned panel.
Compare against your values.

[mike ryan]

Thanks Rob,

This is drivin me crazy lol. I actually had that , and had the names being rpinted in the getCurrentPanel() method

if the card showing was "DICHTE" then it printed

Dichte
true
false
false

if the next card "MASSE" was showing it printed

false
Masse
true
false

but every time i tried to use

if(currentPanel.equals(DICHTE )) i always got a null pointer exception? i thought i finally had it worked out but not quite !!

thanks for your time Rob this just has me stumped good

[Rob Spoor]

The NPE means that currentPanel was null, but that makes sense: the currentPanel you return in your latest method is not the loop variable, that goes out of scope when the loop ends. It's the instance field, and that never gets set.

[mike ryan]

Thanks for the explaination, first 8 hours at work, then i will get back on it!!

Mike

[mike ryan]

ok i have tried this too long lol it is slowly drivin me insane. Can't figure it out !?!

[mike ryan]

Hi again;)

So i have been trying this further as i can't give up!!! I have a couple more questions though...

I have this now to figure out which card is visible

public Component getCurrentPanel(){         

        for(Component currentPanel:cards.getComponents()) {  

          
            if(currentPanel.isVisible() && currentPanel != null){

              
                this.currentPanel=currentPanel;
                
                  System.out.println("i am the current panel "+currentPanel.getName());
            }


        }

        return currentPanel;
    }

and this to check it

class MyListener extends JPanel implements ActionListener,ItemListener {      

        @Override  
        public void actionPerformed(ActionEvent e){      

            if(e.getActionCommand().equals("End"))  

                System.exit(0);  

            if(e.getActionCommand().equals("Compute")&& getCurrentPanel().getName().toString().equals(DICHTE)){


                 System.out.println(currentPanel.getName());

            }             

            else if(e.getActionCommand().equals("Compute")&& getCurrentPanel().getName().toString().equals(MASSE)){                

                 System.out.println(currentPanel.getName()); 
                
            }

            else if(e.getActionCommand().equals("Compute")&& getCurrentPanel().getName().toString().equals(VOLUME)){



               System.out.println(currentPanel.getName());
            }
            

        }

but i am still thinking this isn't the proper way completely as the output is showing dichte once, then masse twice, and volume three times?, but just having System.out.println(currentPanel.getName()); it shows the current
panel properly . Also if this is the correct way to do it, then how do then use the user input on the JTextField then? I have tried just setting the text when the panel is dichte, but the text first gets set when i click "Compute" on the volume panel??? Sorry i am still really confused .

i am the current panel dichte
dichte
i am the current panel masse
i am the current panel masse
masse
i am the current panel volume
i am the current panel volume
i am the current panel volume
volume

Thanks in advance for any help
Mike

[Darryl Burke]

This typically happens when you add a Listener within the event code of the same or another Listener, but you haven't shown us the code that does that.

Also, getName() returns a String, so it is redundant to call toString().

[mike ryan]

Darryl Burke wrote:This typically happens when you add a Listener within the event code of the same or another Listener, but you haven't shown us the code that does that.

Also, getName() returns a String, so it is redundant to call toString().

Thanks Darryl,

ok here is the code that creates and adds the panels

   //Create the "cards"////////////  
        // create dichte panel////////////////////

        JPanel dichte = new JPanel();
        dichte.setLayout(new GridLayout(0,2,2,2));
        dichte.setName("dichte");

        MyListener listener = new MyListener();

        eingabe1 = new JTextField(10);  
        eingabe2 = new JTextField(10);
        answer = new JLabel("");
        end = new JButton("end");
        end.setActionCommand("End");
        end.addActionListener(listener);
        compute = new JButton("compute");
        compute.setActionCommand("Compute");
        compute.addActionListener(listener);

        dichte.add(new JLabel("masse:")); 
        dichte.add((eingabe1));
        dichte.add(new JLabel("volume:"));   
        dichte.add(eingabe2);
        dichte.add(end);    
        dichte.add(compute);
        dichte.add(new JLabel("answer"));
        dichte.add(answer);
        
        // create masse panel///////////////////////////
        JPanel masse = new JPanel();
        masse.setName("masse");
        masse.setLayout(new GridLayout(0,2,2,2));

        eingabe1 = new JTextField(10);  
        eingabe2 = new JTextField(10);
        answer = new JLabel("");
        end = new JButton("end");
        end.setActionCommand("End");
        end.addActionListener(listener);
        compute = new JButton("compute");
        compute.setActionCommand("Compute");
        compute.addActionListener(listener);

        masse.add(new JLabel("dichte:")); 
        masse.add((eingabe1));
        masse.add(new JLabel("volume:"));   
        masse.add(eingabe2);
        masse.add(end);    
        masse.add(compute);
        masse.add(new JLabel("answer"));
        masse.add(answer);

        // create volume panel//////////////////////

        JPanel volume = new JPanel();
        volume.setName("volume");
        
        volume.setLayout(new GridLayout(0,2,2,2));

        eingabe1 = new JTextField(10);  
        eingabe2 = new JTextField(10);
        answer = new JLabel("");
        end = new JButton("end");
        end.setActionCommand("End");
        end.addActionListener(listener);
        compute = new JButton("compute");
        compute.setActionCommand("Compute");
        compute.addActionListener(listener);

        volume.add(new JLabel("masse:")); 
        volume.add((eingabe1));
        volume.add(new JLabel("dichte:"));   
        volume.add(eingabe2);
        volume.add(end);    
        volume.add(compute);
        volume.add(new JLabel("answer"));
        volume.add(answer);

        //Create the panel that contains the "cards".
        cards = new JPanel(new CardLayout());       

        cards.add(dichte, DICHTE); 
        
        cards.add(masse, MASSE); 
        
        cards.add(volume, VOLUME);

        pane.add(comboBoxPane, BorderLayout.PAGE_START);
        pane.add(cards, BorderLayout.CENTER);

    }

It has the same listener for all three panels , i also tried it with each panel having it's own listener but that didn't change anything.Or maybe the setup in general isn't correct.I can post the entire thing if you want to see that.

Thanks again
Mike