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JPanel not showing up dynamically inside JLayeredPane

I am building a chess program in Java. I am not able to display a jPanel containing the promotion options, on top of the jPanel, i.e. the Board.
The board is inside a JLayeredPane and when a pawn reaches the final square, I instantiate the PromotionOptions panel inside the event handler and revalidate. But the jPanel is not being displayed.
I already tried setting proper Size & Location to the jPanel object, putting revalidate(), also used repaint() method. I also assigned JLayeredPane a layout of null explicitly.
All of the questions already in stackoverflow related to this, was solved by properly setting the layout, which doesn't appear to be the problem here...
// JLayeredPane created here...
class Game extends JFrame {
Game() {
super.setLayout(new TableLayout(new double[][]{{0.5, 475, 0.5}, {0.5, 475, 0.5}}));
JLayeredPane layeredContainer = new JLayeredPane();
layeredContainer.setLayout(null);
Board board = new Board(layeredContainer);
board.arrange();
layeredContainer.add(board, 1);
board.setSize(475, 475);
super.add(layeredContainer, "1, 1");
super.setSize(600, 600);
super.setResizable(false);
super.setDefaultCloseOperation(EXIT_ON_CLOSE);
super.validate();
}
}
// PromotionOptions created here...
public class Board extends JPanel {
//skipping some irrelevant code...
private class PromotionOptions extends JPanel {
private PromotionOptions(PieceColor color) {
super.setSize(50,200);
super.setBackground(Color.WHITE);
super.setLayout(new GridLayout(4, 1));
ImageIcon queenIcon = new ImageIcon(getClass().getResource("/pieceIcons/" + color.abbr + "Q.png"));
ImageIcon rookIcon = new ImageIcon(getClass().getResource("/pieceIcons/" + color.abbr + "R.png"));
ImageIcon bishopIcon = new ImageIcon(getClass().getResource("/pieceIcons/" + color.abbr + "B.png"));
ImageIcon knightIcon = new ImageIcon(getClass().getResource("/pieceIcons/" + color.abbr + "N.png"));
JLabel queenLabel = new JLabel(queenIcon);
JLabel rookLabel = new JLabel(rookIcon);
JLabel bishopLabel = new JLabel(bishopIcon);
JLabel knightLabel = new JLabel(knightIcon);
super.add(queenLabel);
super.add(rookLabel);
super.add(bishopLabel);
super.add(knightLabel);
}
}
// skipping some more irrelevant code...
private void executeMove(Tile clickedTile) {
// skip to where I create the PromotionOption object and add to layeredPane...
case PROMOTION:
moveMade.initialTile.removePiece();
JPanel promotionOptions = new PromotionOptions(colorToMove);
promotionOptions.setLocation(200,200);
layeredPaneContainer.add(promotionOptions, 2);
layeredPaneContainer.revalidate();
break;
// Some more code here
}
// End of Board class...
}
Due to some bug, whenever the pawn reaches the final tile, nothing is displayed and the application continues as it is.

After hours of frustrated debugging, I finally somehow made it work correctly. What I did was I added SwingUtilities.invokeLater() method and passed the code inside it like this..
case PROMOTION:
moveMade.initialTile.removePiece();
SwingUtilities.invokeLater(() -> {
JPanel promotionOptions = new PromotionOptions(colorToMove.opposite);
promotionOptions.setLocation(clickedTile.getLocation());
layeredPaneContainer.add(promotionOptions, 2);
layeredPaneContainer.revalidate();
});
break;

Have a phone keypad and I want to make it a simple addition calculator

I made a simple phone keypad and I want to change a button to add numbers. Right now, the + button simply adds a + to the displayed numbers at the top, but I want that to add the inputted numbers. Like on a calculator, exactly what the + does. And I would like to change the clear button to be an enter button. Here's my partner's and I code so far to make the keypad:
public class Keypad extends JPanel implements ActionListener {
JLabel display;
JButton numButton;
JButton clearButton;
String displayContent = "";
String[] numPadContent = {"1","2","3","4","5","6","7","8","9","+","0"};
ArrayList<JButton> buttonList;
// Keypad constructor class
public Keypad(Container pane) {
// sets the size of the Keypad display
pane.setPreferredSize(new Dimension(320, 335));
// initialize display to hold displayContent
display = new JLabel(displayContent);
display.setPreferredSize(new Dimension(320, 25));
// create lowered bevel border around the display
display.setBorder(BorderFactory.createLoweredBevelBorder());
// add the display to the panel
pane.add(display, BorderLayout.PAGE_START);
// initialize the buttonList
buttonList = new ArrayList<JButton>(12);
JPanel numberPanel = new JPanel();
// set the numberPanel to have a 4row by 3col grid layout
numberPanel.setLayout(new GridLayout(4,3,0,0));
// set the size of the numberPanel
numberPanel.setPreferredSize(new Dimension(320,260));
// create the buttons and add them to the buttonList, properly displaying the numbers
for (int i = 0; i < numPadContent.length; i++) {
numButton = new JButton(numPadContent[i]);
buttonList.add(numButton);
}
// add the buttonList to the number panel
for (int n = 0; n < buttonList.size(); n++) {
buttonList.get(n).addActionListener(this);
numberPanel.add(buttonList.get(n));
}
// create black border around the number panel
numberPanel.setBorder(BorderFactory.createMatteBorder(5, 5, 5, 5, Color.black));
// add number panel to center part of display
pane.add(numberPanel, BorderLayout.LINE_END);
// create Clear button that is actionable
clearButton = new JButton("Clear");
clearButton.setPreferredSize(new Dimension(320, 30));
clearButton.addActionListener(this);
// add Clear button to bottom of display
pane.add(clearButton, BorderLayout.PAGE_END);
}
// update the display depending on clicked button(s)
public void actionPerformed(ActionEvent e) {
String textThere = display.getText();
String additionalText = "";
// add clicked number button text to display
for (int a = 0; a < buttonList.size(); a++) {
if (e.getSource().equals(buttonList.get(a))) {
additionalText = buttonList.get(a).getText();
}
}
// clear display if "Clear" button is clicked
if (e.getSource().equals(clearButton)) {
textThere = "";
}
display.setText(textThere.concat(additionalText));
}
public static void main(String[] args) {
//create and set up the window.
JFrame frame = new JFrame("Keypad");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//set up the content pane.
frame.getContentPane().add(new Keypad(frame));
frame.pack();
frame.setVisible(true);
}

See this link: Is there an eval() function in Java?
You can import javax.script and use the ScriptEngine's eval() method to evaluate your expression.

Trying to display images in multiple JPanels

I'm creating a program that features a grid of 12 JPanels. When the "add image" button is pressed, an image appears in the first JPanel in the grid and a counter is incremented by one. From then onwards, every time the "add image" is clicked again, an image would be added to the next JPanel. For some reason, the button only adds an image to the first JPanel and then stops working. Here's the code I've got so far.
public class ImageGrid extends JFrame {
static JPanel[] imageSpaces = new JPanel[12];
int imageCounter = 0;
ImageGrid() {
this.setTitle("Image Grid");
setSize(750, 750);
setDefaultCloseOperation(EXIT_ON_CLOSE);
JPanel p3 = new JPanel();
p3.setLayout(new GridLayout(3, 4, 10, 5));
p3.setBackground(Color.WHITE);
p3.setOpaque(true);
p3.setBorder(BorderFactory.createEmptyBorder(0, 5, 5, 5));
for (int j = 0; j < imageSpaces.length; j++) {
imageSpaces[j] = setImageSpace();
p3.add(imageSpaces[j]);
}
MyButtonPanel p1 = new MyButtonPanel();
add(p1, BorderLayout.SOUTH);
add(p3, BorderLayout.CENTER);
}
public JPanel setImageSpace() {
JPanel test;
test = new JPanel();
test.setOpaque(true);
test.setPreferredSize(new Dimension(100, 100));
return test;
}
class MyButtonPanel extends JPanel implements ActionListener {
final JButton addImage = new JButton("Add Image");
ImageIcon lorryPicture = new ImageIcon(ImageGrid.class.getResource("/resources/lorry.png"));
JLabel lorryImage = new JLabel(lorryPicture);
MyButtonPanel() {
add(addImage);
addImage.addActionListener(this);
}
public void actionPerformed(ActionEvent e) {
if (e.getSource() == addImage) {
imageSpaces[imageCounter].add(lorryImage);
revalidate();
repaint();
imageCounter++;
}
}
}
public static void main(String[] args) {
ImageGrid test = new ImageGrid();
test.setVisible(true);
}
}

You should be revalidating and repainting the panel, (which is the containter being affected by the addition), not the frame
imageSpaces[imageCounter].add(lorryImage);
imageSpaces[imageCounter].revalidate();
imageSpaces[imageCounter].repaint();
Diclaimer: This may work as a simple fix, but also note that a component (in this case your JLabel lorryImage) can only have one parent container. The reason the above fix still works is because you don't revalidate and repaint the previous panel, the label was added to. So you may want to think about doing it correctly, and adding a new JLabel to each panel.
if (e.getSource() == addImage) {
JLabel lorryImage = new JLabel(lorryPicture);
imageSpaces[imageCounter].add(lorryImage);
imageSpaces[imageCounter].revalidate();
imageSpaces[imageCounter].repaint();
imageCounter++;
}
Disclaimer 2: You should add a check, to only add a label if the count is less than the array length, as to avoid the ArrayIndexOutOfBoundsException
Side Notes
Swing apps should be run from the Event Dispatch Thread (EDT). You can do this by wrapping the code in the main in a SwingUtilities.invokeLater(...). See more at Initial Threads
You could also just use a JLabel and call setIcon, instead of using a JPanel

java gui NullPointerException

I keep getting a null pointer exception at the line between the * lines when I click. I've been looking at it for about an hour and cant seem to figure out why. Any help would be greatly appreciated. Thanks.
private Color currentColor;
private char currentChar;
private Letter letter;
private JComboBox comboBox;
private JPanel controlPanel;
private Color[] colorArray = {Color.black,Color.blue,Color.cyan,Color.orange,Color.white,Color.yellow};
private String[] colorStringArray = {"black","blue","cyan","orange","white","yellow"};
private ArrayList<Letter> letterList;
private JButton button1;
private Canvas canvas;
public WholePanel()
{
comboBox = new JComboBox(colorStringArray);
// here we use black to draw a letter
currentColor = colorArray[Color.black];
// set the default character to 'A'
currentChar = 'A';
button1 = new JButton("Undo");
controlPanel = new JPanel();
controlPanel.add(button1);
controlPanel.add(comboBox);
canvas = new Canvas();
JSplitPane sp = new JSplitPane(JSplitPane.VERTICAL_SPLIT, controlPanel, canvas);
canvas.addMouseListener(new PointListener());
add(sp);
// make this panel listen to mouse
addMouseListener(new PointListener());
setBackground(Color.white);
//This method needs to be called for this panel to listen to keys
//When panel listens to other things, and go back to listen
//to keys, this method needs to be called again.
requestFocus();
}
private class PointListener implements MouseListener
{
int x;
int y;
// when a user clicks the panel (applet),
// KeyListener is focused in it.
public void mousePressed(MouseEvent event)
{
x = event.getX();
y = event.getY();
letter = new Letter(x,y,currentChar,colorArray[comboBox.getSelectedIndex()]);
//******************************
letterList.add(letter);
//******************************
for(Letter letter1 : letterList)
{
letter1.Draw(getGraphics());
}
x=y=0;
requestFocus();
}
}
}

You didn't initialize letterList.
Add the following line to your constructor for WholePanel:
letterList = new ArrayList<Letter>();

Creating a Panel of Button GUI

I'm trying to create a board for a game, i first made a frame then if the user //enters the rows and columns as numbers and pushes the start button, it should remove all //whats on frame and add a panel with a grid layout having buttons everywhere
Here is the code ( Problem is the frame gets cleared and nothing appears)
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class Frame extends JFrame implements ActionListener{
private static final long serialVersionUID = 1L;
JButton newButton;
JButton Start;
JTextArea row;
JTextArea col;
JLabel background;
JLabel rows;
JLabel columns;
JLabel Error;
JPanel myPanel;
JCheckBox box;
public Frame()
{
//adding frame
setTitle("DVONN Game");
setSize(1000, 700);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(null);
//making start button
Start = new JButton(new ImageIcon("Start"));
Start.setBounds(500, 30, 300, 300);
Start.setOpaque(true);
Start.addActionListener(this);
//make background
background = new JLabel();
background.setBounds(0, -300, 2000, 1500);
background.setIcon(Color.BLUE));
rows = new JLabel("Enter the rows");
columns = new JLabel("Enter the columns");
rows.setForeground(Color.WHITE);
columns.setForeground(Color.WHITE);
rows.setBounds(10,10,100,30);
columns.setBounds(10,45,105,30);
row = new JTextArea();
col = new JTextArea();
row.setBounds(120,10,100,30);
col.setBounds(120,45,100,30);
Error = new JLabel("Enter numbers plz!");
Error.setBounds(10, 100, 400, 30);
Error.setForeground(Color.RED);
Error.setVisible(true);
box = new JCheckBox("Enable Random Filling");
box.setBounds(10, 200, 150, 20);
box.setVisible(true);
myPanel = new JPanel();
myPanel.setBounds(30, 30, 700, 500);
myPanel.setVisible(true);
newButton = new JButton();
newButton.setOpaque(true);
getContentPane().add(box);
getContentPane().add(rows);
getContentPane().add(columns);
getContentPane().add(row);
getContentPane().add(col);
getContentPane().add(Start);
getContentPane().add(background);
this.validate();
this.repaint();
}
public static void main(String[]args)
{
new Frame();
}
//adding actions for start button
public void actionPerformed(ActionEvent e) {
boolean flag = true;
String r1 = row.getText();
String c1 = col.getText();
int x = 0,y = 0;
try{
x = Integer.parseInt(r1);
y = Integer.parseInt(c1);
} catch(NumberFormatException l) {
flag = false;
}
int size = x * y;
if (flag == true) {
this.getContentPane().removeAll();
this.validate();
this.repaint();
myPanel.setLayout(new GridLayout(x, y));
while(size != 0)
{
myPanel.add(newButton);
size --;
}
this.getContentPane().add(myPanel);
} else {
this.getContentPane().add(Error);
}
}
}

There are several issues with this code
Is it really needed to post that much code. A simple UI with one button to press, and then another component which should appear would be sufficient for an SSCCE
The use of null layout's. Please learn to use LayoutManagers
Each Swing component can only be contained once in the hierarchy. So this loop is useless since you add the same component over and over again (not to mention that a negative size would result in an endless loop)
while(size != 0){
myPanel.add(newButton);
size --;
}
Have you tried debugging to see whether size is actually >0. Since you silently ignore ParseExceptions you might end up with a size of 0 which will clean the content pane and add nothing
Then do as goldilocks suggests and call validate after adding the components. See the javadoc of the Container#add method
This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to display the added component.

Call validate() and repaint() after the new elements have been added instead of after the old ones have been removed.
You don't need to be calling setVisible() on individual components, call it after pack() on the Frame itself, and you shouldn't use validate() and repaint() in the constructor. Ie, replace those with:
pack();
setVisible(true);
or you can do that on the object after the constructor is called.

Try to replace
public static void main(String[]args)
{
new Frame();
}
by
public static void main(String[]args)
{
new Frame().setVisible(true);
}

Remove the call to this.setVisible in the constructor and make this your main method.
public static void main(String[] args) {
final Frame fr = new Frame();
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
fr.setVisible(true);
}
});
}
This will make sure that the frame elements will be in place before it becomes visible.