CardLayout : problem on previous card

Question

I have a frame that is composed of several panels. One of those is a DisplayPanel for displaying drawings. I use CardLayout to display the drawings. Therefore, the uses can click on the next/previous button to look at the next/previous card of drawing that is shown in the displayPanel. I test the "next" button, and it works okay.
However, when I click on the "previous button", it DOES NOT show the exact drawings that I have before navigating to the next card.
Does anyone have any clue on why this will happen and how can I fix that?
Here's the skeleton of my coding:
public class drawMap extends JPanel
     // variable declaration
     public drawMap(Vector mapData, int index)
     public Dimension getPreferredSize()
          return new Dimension(width, height);
     public void paintComponent(Graphics g)
          // loop throught the mapData vector starting from the
          //       given index that is got from the constructor
          // draw two rows
public class DisplayPanel extends JPanel implements ActionListener
     private JButton previousButton, nextButton;
     private JPanel allMaps = new JPanel(new CardLayout());
     DisplayPanel()
          add(mapPanel);
          add(buttonPanel);
     private JPanel mapPanel()
          int i=0, cardIndex=0;
          while (i < mapData.size())
               DrawMap map = new DrawMap(mapData, i)
               allMaps.add(map, String.valueOf(cardIndex));
               i = findNextIndex(); // find the next index to start for the mapData
               cardIndex++;
     private JPanel buttonPanel()
          JPanel p = new JPanel();
          previousButton = new JButton("Previous");
          previousButton.addActionListener(this);
          nextButton = new JButton("Next");
          nextButton.addActionListener(this);
          p.add(previousButton);
          p.add(nextButton);
          return p;
     private int findNextIndex()
          // find the next index to start
     public void actionPerformed(ActionEvent event)
          Object source = event.getSource();
          CardLayout cards = (CardLayout) (allMaps.getLayout());
          if (source == previousButton)
               cards.previous(allMaps);
          else if (source == nextButton)
               cards.next(allMaps);
}

Answer 1

Sorry for the long code. I minimize it as much as I can.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.awt.*;
public class MapFrame extends JPanel
    private SelectionList selection;
    private DisplayPanel display;
    public static void main(String[] args)
        javax.swing.SwingUtilities.invokeLater(new Runnable()
            public void run()
                createAndShowGUI();
    private static void createAndShowGUI()
        JFrame frame = new JFrame("Drawing");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new MapFrame());
        frame.pack();
        frame.setVisible(true);
        frame.setSize(500,500);
        frame.setLocationRelativeTo(null);
    public void setSelection(int c)
         display.setChoice(c);
    public MapFrame ()
        setLayout(new BorderLayout(5, 5));
        setPreferredSize(new Dimension(200, 200));
        add(display = new DisplayPanel(), BorderLayout.CENTER);
        add(selection = new SelectionList(this), BorderLayout.WEST);     
class SelectionList extends JPanel implements ActionListener
     private MapFrame parent;
     private JRadioButton circleRadio, rectRadio;
     private static final int CIRCLE = 1;
     private static final int RECT = 2;
     public SelectionList(MapFrame theParent)
          this.parent = theParent;
          add(radioButton());
     public JPanel radioButton()
          JPanel p = new JPanel(new GridLayout(2,1));     
          circleRadio = new JRadioButton("Circle");
          rectRadio = new JRadioButton("Rect");
          circleRadio.addActionListener(this);
          rectRadio.addActionListener(this);
          ButtonGroup group = new ButtonGroup();
          group.add(circleRadio);
          group.add(rectRadio);
          p.add(circleRadio);
          p.add(rectRadio);
          return p;
     public void actionPerformed(ActionEvent event)
          Object source = event.getSource();
          if (source == circleRadio)
               parent.setSelection(CIRCLE);
          else if (source == rectRadio)
               parent.setSelection(RECT);
class DisplayPanel extends JPanel implements ActionListener
     private static final int CIRCLE = 1;
     private static final int RECT = 2;
    private JButton previousButton, nextButton;
     private int choice = 0;
     private JPanel allMaps = new JPanel(new CardLayout());
     int [] list = {200, 100, 150, 100, 80, 125, 240};
     public DisplayPanel()
          GridBagConstraints gbc = new GridBagConstraints();
          gbc.anchor = GridBagConstraints.CENTER;
          gbc.insets = new Insets (5, 5, 5, 5);
          gbc.fill = GridBagConstraints.NONE;
          gbc.gridx = 0; gbc.gridy = 0; add(mapPanel(), gbc);
          gbc.gridy = 1; add(buttonPanel(), gbc);
     public void setChoice(int i)
          if (i == CIRCLE)
               choice = CIRCLE;
          else
               choice = RECT;
          mapPanel();
     private JPanel mapPanel()
          allMaps.removeAll();
          allMaps.validate();
          int i = 0;
          int cardIndex = 0;
          if (choice != 0)
               while (i < list.length)
                    DrawMap map = new DrawMap(choice, i, list);
                    allMaps.add(map, String.valueOf(cardIndex));
                    int temp = findNextStart(map, i);
                    i = temp;                         
                    cardIndex++;
               allMaps.validate();                    
          else
               DrawMap map = new DrawMap(choice, i, null);
               allMaps.add(map, String.valueOf(0));
               allMaps.validate();
          return allMaps;
     public int findNextStart(DrawMap map, int i)
          int x = 0;
          int index = i;
          while (x <= 1)
               int curXPosition = 0;
               int nextLength = 0;
               while (curXPosition + nextLength <= 400 && index < list.length)
                    int length = list[index];          
                    curXPosition += length;
                    index++;
                    if (index < list.length)
                         nextLength = list[index];
               x++;
          return index;
     private JPanel buttonPanel()
          JPanel p = new JPanel();
          previousButton = new JButton("Previous");     
          previousButton.addActionListener(this);
          nextButton = new JButton("Next");     
          nextButton.addActionListener(this);
          p.add(previousButton);
          p.add(nextButton);
          return p;
     public void actionPerformed(ActionEvent event)
          Object source = event.getSource();
          CardLayout cards = (CardLayout) (allMaps.getLayout());
          if (source == previousButton)
               cards.previous(allMaps);
          else if (source == nextButton)
               cards.next(allMaps);
class DrawMap extends JPanel
     private static final int D_WIDTH = 400;
     private static final int D_HEIGHT = 400;
     private static final int CIRCLE = 1;
     private static final int RECT = 2;
     int width, height;
     int choice;
     int [] list;
     int index;
     public DrawMap(int c, int counter, int[] l)
          width = D_WIDTH;
          height = D_HEIGHT;
          choice = c;
          index = counter;
          list = l;
     public Dimension getPreferredSize()
          return new Dimension(width, height);
     public void paintComponent(Graphics g)
          super.paintComponent(g);
          Graphics2D g2d = (Graphics2D) g;
          if (list != null)
               int x = 0;
               while (x <= 1)
                    int gridYLine = (height/2) * x;
                    int curXPosition = 0;
                    int nextLength = 0;
                    while (curXPosition + nextLength <= width && index < list.length)
                         int length = list[index];
                         if (choice == CIRCLE)
                              g2d.drawOval(curXPosition, gridYLine, length, length);
                         else
                              g2d.drawRect(curXPosition, gridYLine,length, length);
                         curXPosition += length;
                         index++;
                         if (index < list.length)
                              nextLength = list[index];
                    x++;
}