I'm currently working on a project to predict moves in chess based on the position, I am using an action listener for my array of buttons (like JButton[][]).
Below is the error I'm getting...
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "javax.swing.JButton.getIcon()" because "this.chessboardButtons[cord_x][cord_y]" is null
at Homework6_Alex.ChessBoard.actionPerformed(ChessBoard.java:151)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6614)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at java.desktop/java.awt.Component.processEvent(Component.java:6379)
at java.desktop/java.awt.Container.processEvent(Container.java:2263)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4990)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4822)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4919)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4548)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4489)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2769)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4822)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Below this is the code I'm working with for the ActionListener portion. Any ideas on how I can solve this?
@Override
public void actionPerformed(ActionEvent e){
if (e.getSource() instanceof JButton) {
//System.out.println(chessboardButtons[((JButton)e.getSource()).getX()][((JButton) e.getSource()).getY()].getLocation());
int x = ((JButton) e.getSource()).getX();
int y = ((JButton) e.getSource()).getY();
int cord_y = (y /8)/8;
int cord_x = (x /8)/8;
System.out.println(cord_x + " " + cord_y);
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteKingIcon) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteQueenIcon) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteBishop1Icon) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteRook1Icon ) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whitePawn1Icon) {
chessboardButtons[cord_x +1][cord_y].setBackground(Color.red);
chessboardButtons[cord_x +1][cord_y].setOpaque(true);
chessboardButtons[cord_x +2][cord_y].setBackground(Color.red);
chessboardButtons[cord_x +2 ][cord_y].setOpaque(true);
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteKnight1Icon) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == null) {
//Instructions instructions = new Instructions();
System.out.println("rules");
}
}
Additional Side Note: when using the .getLocation() for buttons my point I get are increases of 75, from X 0 - 525 to Y 0-525 so a board of 525, 525. I am using a gridLayout 8,8.
Below is my whole class for more information:
public class ChessBoard extends JFrame implements ActionListener{
JLayeredPane layeredpane;
JPanel chessboard;
JButton[][] chessboardButtons;
Color black;
JLabel whiteKing;
JLabel whiteQueen;
JLabel whiteRook1;
JLabel whiteRook2;
JLabel whiteBishop1;
JLabel whiteBishop2;
JLabel whiteKnight1;
JLabel whiteKnight2;
JLabel whitePawn1;
JLabel whitePawn2;
JLabel whitePawn3;
JLabel whitePawn4;
JLabel whitePawn5;
JLabel whitePawn6;
JLabel whitePawn7;
JLabel whitePawn8;
ImageIcon whiteKingIcon = new ImageIcon("/Users/aengelsr/Cs245intellij/src/Homework6_Alex/Icons/white_king.jpeg");
ImageIcon whiteQueenIcon = new ImageIcon("/Users/aengelsr/Cs245intellij/src/Homework6_Alex/Icons/white_queen.jpeg");
ImageIcon whiteRook1Icon = new ImageIcon("/Users/aengelsr/Cs245intellij/src/Homework6_Alex/Icons/white_rook.jpeg");
ImageIcon whiteBishop1Icon = new ImageIcon("/Users/aengelsr/Cs245intellij/src/Homework6_Alex/Icons/white_bishop.jpeg");
ImageIcon whiteKnight1Icon = new ImageIcon("/Users/aengelsr/Cs245intellij/src/Homework6_Alex/Icons/white_knight.jpeg");
ImageIcon whitePawn1Icon = new ImageIcon("/Users/aengelsr/Cs245intellij/src/Homework6_Alex/Icons/white_pawn.jpeg");
ArrayList<ImageIcon> whitelist;
List<Integer> blackPeices;
UIManager Ui;
ChessBoard() throws IndexOutOfBoundsException {
Dimension Size = new Dimension(600, 600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(true);
setLocationRelativeTo(null);
setSize(600, 600);
setTitle("Chess Board");
layeredpane = new JLayeredPane();
getContentPane().add(layeredpane);
layeredpane.setPreferredSize(Size);
chessboard = new JPanel();
layeredpane.add(chessboard, JLayeredPane.DEFAULT_LAYER);
chessboard.setLayout(new GridLayout(8, 8));
chessboard.setPreferredSize(Size);
chessboard.setBounds(0, 0, Size.width, Size.height);
Ui = new UIManager();
chessboardButtons = new JButton[9][9];
black = Color.black;
for (int i = 0; i < 8; i++) {
for (int j = 0; j < 8; j++) {
chessboardButtons[i][j] = new JButton();
chessboardButtons[i][j].setBorderPainted(false);
//chessboardButtons[i][j].setText(String.valueOf(i * 8 + j));
if ((i + j) % 2 != 0) {
chessboardButtons[i][j].setBackground(black);
chessboardButtons[i][j].setOpaque(true);
}
chessboard.add(chessboardButtons[i][j]);
chessboardButtons[i][j].addActionListener(this);
}
}
whitelist = new ArrayList<ImageIcon>();
whitelist.add(whiteKingIcon);
whitelist.add(whiteQueenIcon);
whitelist.add(whiteRook1Icon);
whitelist.add(whiteBishop1Icon);
whitelist.add(whiteKnight1Icon);
whitelist.add(whitePawn1Icon);
blackPeices = new ArrayList<>();
Collections.shuffle(whitelist);
Collections.shuffle(blackPeices);
System.out.println(whitelist);
for(int i = 0; i < whitelist.size(); i++) {
int random_x = (int) (Math.random() * 8);
int random_y = (int) (Math.random() * 8);
chessboardButtons[random_x][random_y].setIcon(whitelist.get(i));
}
for(int i = 0; i < whitelist.size(); i++) {
int random_x = (int) (Math.random() * 8);
int random_y = (int) (Math.random() * 8);
chessboardButtons[random_x][random_y].setIcon((new ImageIcon("/Users/aengelsr/Cs245intellij/src/Homework6_Alex/Icons/white_pawn.jpeg")));
}
setVisible(true);
pack();
}
@Override
public void actionPerformed(ActionEvent e){
if (e.getSource() instanceof JButton) {
//System.out.println(chessboardButtons[((JButton)e.getSource()).getX()][((JButton) e.getSource()).getY()].getLocation());
int x = ((JButton) e.getSource()).getX();
int y = ((JButton) e.getSource()).getY();
int cord_y = (y /8)/8;
int cord_x = (x /8)/8;
System.out.println(cord_x + " " + cord_y);
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteKingIcon) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteQueenIcon) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteBishop1Icon) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteRook1Icon ) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whitePawn1Icon) {
chessboardButtons[cord_x +1][cord_y].setBackground(Color.red);
chessboardButtons[cord_x +1][cord_y].setOpaque(true);
chessboardButtons[cord_x +2][cord_y].setBackground(Color.red);
chessboardButtons[cord_x +2 ][cord_y].setOpaque(true);
}
if (chessboardButtons[cord_x][cord_y].getIcon() == whiteKnight1Icon) {
System.out.println("Nothing");
}
if (chessboardButtons[cord_x][cord_y].getIcon() == null) {
//Instructions instructions = new Instructions();
System.out.println("rules");
}
}
}
}
Thank you!
My chessboard with random placement
and finally a another note - we don't actually have to get this to play chess, only show visually possible moves of each peice even if there a another "peice" in the way, that in real life would make the move impossible
