JButton not visible after use of Jpanel removeAll ..

Question

Hi!
I'm having a calculator class that inherits JFrame. I need to add more buttons after setting an option from the (view) menu bar .. (from normal to scientific calculator). I needed to use the JPanel removeAll method and then add the normal buttons plus extra buttons. But the problem is, that the Buttons are only visible when I touch them with the mouse.
Does anybody know why? Thanks for your help!
See code below (still in construction phase):
Name: Hemanth. B
Original code from Website: java-swing-tutorial.html
Topic : A basic Java Swing Calculator
Conventions Used in Source code
     1. All JLabel components start with jlb*
     2. All JPanel components start with jpl*
     3. All JMenu components start with jmenu*
     4. All JMenuItem components start with jmenuItem*
     5. All JDialog components start with jdlg*
     6. All JButton components start with jbn*
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Calculator extends JFrame
implements ActionListener {
// Constants
final int NORMAL = 0;
final int SCIENTIFIC = 8;
final int MAX_INPUT_LENGTH = 20;
final int INPUT_MODE = 0;
final int RESULT_MODE = 1;
final int ERROR_MODE = 2;
// Variables
int displayMode;
int calcType = SCIENTIFIC;
boolean clearOnNextDigit, percent;
double lastNumber;
String lastOperator, title;
private JMenu jmenuFile, jmenuView, jmenuHelp;
private JMenuItem jmenuitemExit, jmenuitemAbout;
private JRadioButtonMenuItem jmenuItemNormal = new JRadioButtonMenuItem("Normal");
private JRadioButtonMenuItem jmenuItemScientific = new JRadioButtonMenuItem("Scientific");
private     ButtonGroup viewMenuButtonGroup = new ButtonGroup();
private JLabel jlbOutput;
private JButton jbnButtons[];
private JPanel jplButtons, jplMaster, jplBackSpace, jplControl;
* Font(String name, int style, int size)
Creates a new Font from the specified name, style and point size.
Font f12 = new Font("Verdana", 0, 12);
Font f121 = new Font("Verdana", 1, 12);
// Constructor
public Calculator(String title) {
/* Set Up the JMenuBar.
* Have Provided All JMenu's with Mnemonics
* Have Provided some JMenuItem components with Keyboard Accelerators
     //super(title);
     this.title = title;
     //displayCalculator(title);
}     //End of Contructor Calculator
private void displayCalculator (String title) {
     //add WindowListener for closing frame and ending program
     addWindowListener (
     new WindowAdapter() {     
     public void windowClosed(WindowEvent e) {
     System.exit(0);
     //setResizable(false);
//Set frame layout manager
     setBackground(Color.gray);
     validate();
     createMenuBar();
     createMasterPanel();      
     createDisplayPanel();
     clearAll();
     this.getContentPane().validate();
     requestFocus();
     pack();
     //getContentPane().
     setVisible(true);
private void createMenuBar() {
jmenuFile = new JMenu("File");
jmenuFile.setFont(f121);
jmenuFile.setMnemonic(KeyEvent.VK_F);
jmenuitemExit = new JMenuItem("Exit");
jmenuitemExit.setFont(f12);
jmenuitemExit.setAccelerator(KeyStroke.getKeyStroke( KeyEvent.VK_X,
                                        ActionEvent.CTRL_MASK));
jmenuFile.add(jmenuitemExit);
jmenuView = new JMenu("View");
jmenuFile.setFont(f121);
jmenuFile.setMnemonic(KeyEvent.VK_W);
jmenuItemNormal.setMnemonic(KeyEvent.VK_N);
viewMenuButtonGroup.add(jmenuItemNormal);
jmenuView.add(jmenuItemNormal);
jmenuItemScientific.setMnemonic(KeyEvent.VK_S);
viewMenuButtonGroup.add(jmenuItemScientific);
jmenuView.add(jmenuItemScientific);
if (jmenuItemNormal.isSelected() == false &&
jmenuItemScientific.isSelected() == false)
jmenuItemScientific.setSelected(true);
     jmenuHelp = new JMenu("Help");
     jmenuHelp.setFont(f121);
     jmenuHelp.setMnemonic(KeyEvent.VK_H);
     jmenuitemAbout = new JMenuItem("About Calculator");
     jmenuitemAbout.setFont(f12);
     jmenuHelp.add(jmenuitemAbout);
     JMenuBar menubar = new JMenuBar();
     menubar.add(jmenuFile);
     menubar.add(jmenuView);
     menubar.add(jmenuHelp);
     setJMenuBar(menubar);
     jmenuItemNormal.addActionListener(this);
     jmenuItemScientific.addActionListener(this);
     jmenuitemAbout.addActionListener(this);
     jmenuitemExit.addActionListener(this);
private void createDisplayPanel() {
     if (jlbOutput != null) {
     jlbOutput.removeAll();     
     jlbOutput = new JLabel("0",JLabel.RIGHT);
     jlbOutput.setBackground(Color.WHITE);
     jlbOutput.setOpaque(true);
     // Add components to frame
     getContentPane().add(jlbOutput, BorderLayout.NORTH);
     jlbOutput.setVisible(true);
private void createMasterPanel() {
     if (jplMaster != null) {
     jplMaster.removeAll();     
     jplMaster = new JPanel(new BorderLayout());
     createCalcButtons();      
     jplMaster.add(jplBackSpace, BorderLayout.WEST);
     jplMaster.add(jplControl, BorderLayout.EAST);
     jplMaster.add(jplButtons, BorderLayout.SOUTH);
     ((JPanel)getContentPane()).revalidate();
     // Add components to frame
     getContentPane().add(jplMaster, BorderLayout.SOUTH);
     jplMaster.setVisible(true);
private void createCalcButtons() {
     int rows = 4;
     int cols = 5 + calcType/rows;
     jbnButtons = new JButton[31];
     // Create numeric Jbuttons
     for (int i=0; i<=9; i++) {
     // set each Jbutton label to the value of index
     jbnButtons[i] = new JButton(String.valueOf(i));
     // Create operator Jbuttons
     jbnButtons[10] = new JButton("+/-");
     jbnButtons[11] = new JButton(".");
     jbnButtons[12] = new JButton("=");
     jbnButtons[13] = new JButton("/");
     jbnButtons[14] = new JButton("*");
     jbnButtons[15] = new JButton("-");
     jbnButtons[16] = new JButton("+");
     jbnButtons[17] = new JButton("sqrt");
     jbnButtons[18] = new JButton("1/x");
     jbnButtons[19] = new JButton("%");
     jplBackSpace = new JPanel();
     jplBackSpace.setLayout(new GridLayout(1, 1, 2, 2));
     jbnButtons[20] = new JButton("Backspace");
     jplBackSpace.add(jbnButtons[20]);
     jplControl = new JPanel();
     jplControl.setLayout(new GridLayout(1, 2, 2 ,2));
     jbnButtons[21] = new JButton(" CE ");
     jbnButtons[22] = new JButton("C");
     jplControl.add(jbnButtons[21]);
     jplControl.add(jbnButtons[22]);
     //if (calcType == SCIENTIFIC) {     
     jbnButtons[23] = new JButton("s");
     jbnButtons[24] = new JButton("t");
     jbnButtons[25] = new JButton("u");
     jbnButtons[26] = new JButton("v");
     jbnButtons[27] = new JButton("w");
     jbnButtons[28] = new JButton("x");
     jbnButtons[29] = new JButton("y");
     jbnButtons[30] = new JButton("z");
// Setting all Numbered JButton's to Blue. The rest to Red
     for (int i=0; i<jbnButtons.length; i++)     {
     //activate ActionListener
     System.out.println("add action listener: " + i);
     jbnButtons.addActionListener(this);
     //set button text font/colour
     jbnButtons[i].setFont(f12);
     jbnButtons[i].invalidate();
     if (i<10)
          jbnButtons[i].setForeground(Color.blue);               
     else
          jbnButtons[i].setForeground(Color.red);
     // container for Jbuttons
     jplButtons = new JPanel(new GridLayout(rows, cols, 2, 2));
System.out.println("Cols: " + cols);      
     //Add buttons to keypad panel starting at top left
     // First row
     // extra left buttons for scientific
     if (calcType == SCIENTIFIC) {
     System.out.println("Adding Scientific buttons");
     setSize(400, 217);
     setLocation(200, 250);
     jplButtons.add(jbnButtons[23]);
     jplButtons.add(jbnButtons[27]);
     } else {
     setSize(241, 217);
     setLocation(200, 250);
     for(int i=7; i<=9; i++)          {
     jplButtons.add(jbnButtons[i]);
     // add button / and sqrt
     jplButtons.add(jbnButtons[13]);
     jplButtons.add(jbnButtons[17]);
     // Second row
     // extra left buttons for scientific
     if (calcType == SCIENTIFIC) {
     System.out.println("Adding Scientific buttons");
     jplButtons.add(jbnButtons[24]);
     jplButtons.add(jbnButtons[28]);
     for(int i=4; i<=6; i++)     {
     jplButtons.add(jbnButtons[i]);
     // add button * and x^2
     jplButtons.add(jbnButtons[14]);
     jplButtons.add(jbnButtons[18]);
     // Third row
     // extra left buttons for scientific
     if (calcType == SCIENTIFIC) {
     System.out.println("Adding Scientific buttons");
     jplButtons.add(jbnButtons[25]);
     jplButtons.add(jbnButtons[29]);
     for( int i=1; i<=3; i++) {
     jplButtons.add(jbnButtons[i]);
     //adds button - and %
     jplButtons.add(jbnButtons[15]);
     jplButtons.add(jbnButtons[19]);
     //Fourth Row
     // extra left buttons for scientific
     if (calcType == SCIENTIFIC) {
     System.out.println("Adding Scientific buttons");
     jplButtons.add(jbnButtons[26]);
     jplButtons.add(jbnButtons[30]);
     // add 0, +/-, ., +, and =
     jplButtons.add(jbnButtons[0]);
     jplButtons.add(jbnButtons[10]);
     jplButtons.add(jbnButtons[11]);
     jplButtons.add(jbnButtons[16]);
     jplButtons.add(jbnButtons[12]);
     jplButtons.revalidate();
// Perform action
public void actionPerformed(ActionEvent e){
     double result = 0;
     if(e.getSource() == jmenuitemAbout) {
     //JDialog dlgAbout = new CustomABOUTDialog(this,
     //                              "About Java Swing Calculator", true);
     //dlgAbout.setVisible(true);
     } else if(e.getSource() == jmenuitemExit) {
     System.exit(0);
if (e.getSource() == jmenuItemNormal) {
calcType = NORMAL;
displayCalculator(title);
if (e.getSource() == jmenuItemScientific) {
calcType = SCIENTIFIC;
displayCalculator(title);
System.out.println("Calculator is set to "
+ (calcType == NORMAL?"Normal":"Scientific") + " :" + jbnButtons.length);      
     // Search for the button pressed until end of array or key found
     for (int i=0; i<jbnButtons.length; i++)     {
     if(e.getSource() == jbnButtons[i]) {
          System.out.println(i);
          switch(i) {
          case 0:
               addDigitToDisplay(i);
               break;
          case 1:
               System.out.println("1");
               addDigitToDisplay(i);
               break;
          case 2:
               addDigitToDisplay(i);
               break;
          case 3:
               addDigitToDisplay(i);
               break;
          case 4:
               addDigitToDisplay(i);
               break;
          case 5:
               addDigitToDisplay(i);
               break;
          case 6:
               addDigitToDisplay(i);
               break;
          case 7:
               addDigitToDisplay(i);
               break;
          case 8:
               addDigitToDisplay(i);
               break;
          case 9:
               addDigitToDisplay(i);
               break;
          case 10:     // +/-
               processSignChange();
               break;
          case 11:     // decimal point
               addDecimalPoint();
               break;
          case 12:     // =
               processEquals();
               break;
          case 13:     // divide
               processOperator("/");
               break;
          case 14:     // *
               processOperator("*");
               break;
          case 15:     // -
               processOperator("-");
               break;
          case 16:     // +
               processOperator("+");
               break;
          case 17:     // sqrt
               if (displayMode != ERROR_MODE) {
               try {
                    if (getDisplayString().indexOf("-") == 0)
                    displayError("Invalid input for function!");
                    result = Math.sqrt(getNumberInDisplay());
                    displayResult(result);
               catch(Exception ex) {
                    displayError("Invalid input for function!");
                    displayMode = ERROR_MODE;
               break;
          case 18:     // 1/x
               if (displayMode != ERROR_MODE){
               try {
                    if (getNumberInDisplay() == 0)
                    displayError("Cannot divide by zero!");
                    result = 1 / getNumberInDisplay();
                    displayResult(result);
               catch(Exception ex) {
                    displayError("Cannot divide by zero!");
                    displayMode = ERROR_MODE;
               break;
          case 19:     // %
               if (displayMode != ERROR_MODE){
               try {
                    result = getNumberInDisplay() / 100;
                    displayResult(result);
               catch(Exception ex) {
                    displayError("Invalid input for function!");
                    displayMode = ERROR_MODE;
               break;
          case 20:     // backspace
               if (displayMode != ERROR_MODE) {
               setDisplayString(getDisplayString().substring(0,
               getDisplayString().length() - 1));
               if (getDisplayString().length() < 1)
                    setDisplayString("0");
               break;
          case 21:     // CE
               clearExisting();
               break;
          case 22:     // C
               clearAll();
               break;
void setDisplayString(String s) {
     jlbOutput.setText(s);
String getDisplayString () {
     return jlbOutput.getText();
void addDigitToDisplay(int digit) {
     if (clearOnNextDigit)
     setDisplayString("");
     String inputString = getDisplayString();
     if (inputString.indexOf("0") == 0) {
     inputString = inputString.substring(1);
     if ((!inputString.equals("0") || digit > 0)
                         && inputString.length() < MAX_INPUT_LENGTH) {
     setDisplayString(inputString + digit);
     displayMode = INPUT_MODE;
     clearOnNextDigit = false;
void addDecimalPoint() {
     displayMode = INPUT_MODE;
     if (clearOnNextDigit)
     setDisplayString("");
     String inputString = getDisplayString();
     // If the input string already contains a decimal point, don't
     // do anything to it.
     if (inputString.indexOf(".") < 0)
     setDisplayString(new String(inputString + "."));
void processSignChange() {
     if (displayMode == INPUT_MODE) {
     String input = getDisplayString();
     if (input.length() > 0 && !input.equals("0"))     {
          if (input.indexOf("-") == 0)
          setDisplayString(input.substring(1));
          else
          setDisplayString("-" + input);
     } else if (displayMode == RESULT_MODE) {
     double numberInDisplay = getNumberInDisplay();
     if (numberInDisplay != 0)
     displayResult(-numberInDisplay);
void clearAll() {
     setDisplayString("0");
     lastOperator = "0";
     lastNumber = 0;
     displayMode = INPUT_MODE;
     clearOnNextDigit = true;
void clearExisting() {
     setDisplayString("0");
     clearOnNextDigit = true;
     displayMode = INPUT_MODE;
double getNumberInDisplay()     {
     String input = jlbOutput.getText();
     return Double.parseDouble(input);
void processOperator(String op) {
     if (displayMode != ERROR_MODE) {
     double numberInDisplay = getNumberInDisplay();
     if (!lastOperator.equals("0")) {
          try {
          double result = processLastOperator();
          displayResult(result);
          lastNumber = result;
          catch (DivideByZeroException e)     {
          displayError("Cannot divide by zero!");
     } else {
     lastNumber = numberInDisplay;
     clearOnNextDigit = true;
     lastOperator = op;
void processEquals() {
     double result = 0;
     if (displayMode != ERROR_MODE){
     try {
          result = processLastOperator();
          displayResult(result);
     catch (DivideByZeroException e) {
          displayError("Cannot divide by zero!");
     lastOperator = "0";
double processLastOperator() throws DivideByZeroException {
     double result = 0;
     double numberInDisplay = getNumberInDisplay();
     if (lastOperator.equals("/")) {
     if (numberInDisplay == 0)
          throw (new DivideByZeroException());
     result = lastNumber / numberInDisplay;
     if (lastOperator.equals("*"))
     result = lastNumber * numberInDisplay;
     if (lastOperator.equals("-"))
     result = lastNumber - numberInDisplay;
     if (lastOperator.equals("+"))
     result = lastNumber + numberInDisplay;
     return result;
void displayResult(double result){
     setDisplayString(Double.toString(result));
     lastNumber = result;
     displayMode = RESULT_MODE;
     clearOnNextDigit = true;
void displayError(String errorMessage){
     setDisplayString(errorMessage);
     lastNumber = 0;
     displayMode = ERROR_MODE;
     clearOnNextDigit = true;
public static void main(String args[]) {
     Calculator calci = new Calculator("My Calculator");
     calci.displayCalculator("My Calculator");
System.out.println("Exitting...");
}     //End of Swing Calculator Class.
class DivideByZeroException extends Exception{
public DivideByZeroException() {
     super();
public DivideByZeroException(String s) {
     super(s);
class CustomABOUTDialog extends JDialog implements ActionListener {
JButton jbnOk;
CustomABOUTDialog(JFrame parent, String title, boolean modal){
     super(parent, title, modal);
     setBackground(Color.black);
     JPanel p1 = new JPanel(new FlowLayout(FlowLayout.CENTER));
     StringBuffer text = new StringBuffer();
     text.append("Calculator Information\n\n");
     text.append("Developer:     Hemanth\n");
     text.append("Version:     1.0");
     JTextArea jtAreaAbout = new JTextArea(5, 21);
     jtAreaAbout.setText(text.toString());
     jtAreaAbout.setFont(new Font("Times New Roman", 1, 13));
     jtAreaAbout.setEditable(false);
     p1.add(jtAreaAbout);
     p1.setBackground(Color.red);
     getContentPane().add(p1, BorderLayout.CENTER);
     JPanel p2 = new JPanel(new FlowLayout(FlowLayout.CENTER));
     jbnOk = new JButton(" OK ");
     jbnOk.addActionListener(this);
     p2.add(jbnOk);
     getContentPane().add(p2, BorderLayout.SOUTH);
     setLocation(408, 270);
     setResizable(false);
     addWindowListener(new WindowAdapter() {
          public void windowClosing(WindowEvent e) {
               Window aboutDialog = e.getWindow();
               aboutDialog.dispose();
     pack();
public void actionPerformed(ActionEvent e) {
     if(e.getSource() == jbnOk) {
     this.dispose();
Message was edited by:
dungorg

Answer 1

Swing related questions should be posted in the Swing forum.
After adding or removing components from a visible panel you need to use panel.revalidate() and sometimes panel.repaint();
If you need further help then you need to create a [url http://homepage1.nifty.com/algafield/sscce.html]Short, Self Contained, Compilable and Executable, Example Program (SSCCE) that demonstrates the incorrect behaviour, because I can't guess exactly what you are doing based on the information provided.
Don't forget to use the [url http://forum.java.sun.com/help.jspa?sec=formatting]Code Formatting Tags so the posted code retains its original formatting.