JPanel revalidate and repaint not working properly (Java Swing)

Question

I am creating a Sudoku game. The game has some buttons such as new game, re-start, solve, etc.

public void inicio() {

    JPanel panel = new JPanel();

    panel.setLayout(null);
    panel.setPreferredSize(new Dimension(735, 620));

 ...

 button2 = new JButton("New Game"); //Other buttons like this one

 ...

 JPanel sudoku = PanelSudoku();
 sudoku.setBounds(228, 90, 470, 470);

 ...
    //Botón nuevo juego
    button2.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {

            ///AQUÍ CÓDIGO  

            setGame();
            panel.remove(sudoku);
            JPanel sudokuNuevo = PanelSudoku();
            sudokuNuevo.setBounds(228, 90, 470, 470);
            panel.add(sudokuNuevo);
            panel.revalidate();
            panel.repaint();


            ///

        }
    });

    //Botón reiniciar juego
    button3.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {

            ///AQUÍ CÓDIGO  

            panel.remove(sudoku);
            JPanel sudokuNuevo = PanelSudoku();
            sudokuNuevo.setBounds(228, 90, 470, 470);
            panel.add(sudokuNuevo);
            panel.revalidate();
            panel.repaint();

            ///

        }
    });

    //Botón Comprobar
    button4.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {

            ///AQUÍ CÓDIGO

            SwingUtilities.invokeLater(new Runnable() {

                public void run() {

                    VentanaKeepTrying ejecutable = new VentanaKeepTrying();
                    //VentanaWinner ejecutable = new VentanaWinner();
                    ejecutable.setVisible(true);

                }
            });

            ///

        }
    });

    //Botón resolver
    button5.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {

            ///AQUÍ CÓDIGO

            SwingUtilities.invokeLater(new Runnable() {

                public void run() {

                    panel.remove(sudoku);
                    JPanel sudokuNuevo = PanelSudokuResuelto();
                    sudokuNuevo.setBounds(228, 90, 470, 470);
                    panel.add(sudokuNuevo);
                    panel.revalidate();
                    panel.repaint();

                }
            });

            ///

        }

  ...

  //Agregar elementos al panel
    panel.add(imagenSudoku);
    panel.add(imagenMenu);
    panel.add(combo1);
    panel.add(button2);
    panel.add(button3);
    panel.add(button4);
    panel.add(button5);
    panel.add(button6);
    panel.add(button7);
    panel.add(button8);
    //panel.add(buttonR);
    panel.add(sudoku);
    panel.add(imagenV2);

    //Agregar panel
    add(panel);

    pack();

    setSize(735, 620);
    setTitle("Sudoku - ©2015 Games V²");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
}

....

 public JPanel PanelSudoku() {

    JPanel panel = new JPanel();

    //panel.setLayout(null);
    panel.setPreferredSize(new Dimension(470, 470));

    JPanel panelSudoku = new JPanel();
    panelSudoku.setPreferredSize(new Dimension(470, 470));
    //panelSudoku.setBackground(Color.WHITE);

    //Espacio en el borde
    panelSudoku.setBorder(BorderFactory.createEmptyBorder(8, 8, 8, 8));

    //Número de filas, columnas, espacio horizontal, espacio vertical.
    panelSudoku.setLayout(new GridLayout(9, 9, 12, 12));

    //Llenar Sudoku con Array del Nível
    for (int i = 0; i < b1.size(); i++) {

        //Casilla vacia
        if (b1.get(i).equals(".")) {

            JTextPane textPane = new JTextPane();
            textPane.setText("");
            textPane.setEditable(true);
            textPane.setFont(new Font("RockoFLF", Font.BOLD, 24));

            //Color azul para la región
            if (i == 0 || i == 1 || i == 2 || i == 9 || i == 10 || i == 11 || i == 18 || i == 19 || i == 20 || i == 6 || i == 7 || i == 8 || i == 15 || i == 16 || i == 17 || i == 24 || i == 25 || i == 26 || i == 30 || i == 31 || i == 32 || i == 39 || i == 40 || i == 41 || i == 48 || i == 49 || i == 50 || i == 54 || i == 55 || i == 56 || i == 63 || i == 64 || i == 65 || i == 72 || i == 73 || i == 74 || i == 60 || i == 61 || i == 62 || i == 69 || i == 70 || i == 71 || i == 78 || i == 79 || i == 80) {
                Color colore = new Color(224, 235, 250); //Lightblue
                textPane.setBackground(colore);
            }

            //Color colore2 = new Color(234, 112, 165);
            Color colore2 = new Color(255, 127, 80); //Orange

            //Estilos - Centrar y Colores de letra
            StyledDocument doc = textPane.getStyledDocument();
            SimpleAttributeSet center = new SimpleAttributeSet();
            StyleConstants.setAlignment(center, StyleConstants.ALIGN_CENTER);
            StyleConstants.setForeground(center, colore2);
            doc.setParagraphAttributes(0, doc.getLength(), center, false);

            //Agregar al panel
            panelSudoku.add(textPane);

            //Para sólo permitir números del 1 al 9
            textPane.addKeyListener(new KeyListener() {

                @Override
                public void keyTyped(KeyEvent e) {

                    //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
                }

                @Override
                public void keyPressed(KeyEvent e) {

                    //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
                }

                @Override
                public void keyReleased(KeyEvent e) {
                    String t = textPane.getText();
                    if (!validarStringEnteroPositivo(t)) {
                        textPane.setText("");
                    } else {

                    }
                    //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
                }
            });

        } 
        //Casilla con número dado al usuario
        else {

            JTextPane textPane = new JTextPane();

            //Poner el número
            textPane.setText((b1.get(i)));
            //Que no se pueda editar
            textPane.setEditable(false);
            //Estilo
            textPane.setFont(new Font("RockoFLF", Font.BOLD, 24));

            //Color azul para la región
            if (i == 0 || i == 1 || i == 2 || i == 9 || i == 10 || i == 11 || i == 18 || i == 19 || i == 20 || i == 6 || i == 7 || i == 8 || i == 15 || i == 16 || i == 17 || i == 24 || i == 25 || i == 26 || i == 30 || i == 31 || i == 32 || i == 39 || i == 40 || i == 41 || i == 48 || i == 49 || i == 50 || i == 54 || i == 55 || i == 56 || i == 63 || i == 64 || i == 65 || i == 72 || i == 73 || i == 74 || i == 60 || i == 61 || i == 62 || i == 69 || i == 70 || i == 71 || i == 78 || i == 79 || i == 80) {
                Color colore = new Color(224, 235, 250);
                textPane.setBackground(colore);
            }

            //Estilos - Centrar y Colores de letra
            StyledDocument doc = textPane.getStyledDocument();
            SimpleAttributeSet center = new SimpleAttributeSet();
            StyleConstants.setAlignment(center, StyleConstants.ALIGN_CENTER);
            StyleConstants.setForeground(center, Color.darkGray);
            doc.setParagraphAttributes(0, doc.getLength(), center, false);

            //Agregar al panel
            panelSudoku.add(textPane);
        }
    }

    //Agregar panel
    panel.add(panelSudoku);

    add(panel);

    //Lo regresa para poderlo útilizar

    return panel;
}

The problem that I am having is that when I press, let's say the solve button and then the new game button, the new game that appears gets all funny and doesn't work as it should.

I'm just learning JavaSwing, so any help would be greatly appreciated! :)

Answer 1

I think it is because actually you're not removing a JPanel with previously used sudoku board, before adding another one. Try:

panel.remove(sudoku);
sudoku = PanelSudoku();
panel.add(sudoku);
panel.revalidate();
panel.repaint();

Right now you add new sudokuNuevo on a top of another.