Hey all,
I have been busy building my own chess game and as of now im a bit stomped.
Well you see i have an object Board, this object will be initiated and it will create a new frame with various panels one of them being the panel which holds the squares of the board, inside that panel i create a grid of panels, with pictures as backgrounds(blocks for the chess board either black or white), and to each of those panels i add a jlabel, which in the future will hold the image of the piece on the board. Now when creating the panels i labeled them so i may know what co-ordinates of the piece are i.e A-H and 1-8. I lable the usingthe setName() method, each of the ImagePanels and labels are declared globally.
The problem is that i have a method -listLabelNames() that will list the names of the lables/panels ie A1-H8. When i call the method from within the instance after the frame has added all its components, the method works fine and prints out the array of the panels/labels names. However when i iniate board and call the listLabelNames() method from the object which iniated board the array returns a null pointer.
My thoughts are that in the calling class the statement which creates a new instance of board doesnt wait until the instnce/frame is fully created... And then when i call listLabelNames() the array isnt yet filled. I cant seem to find an answer/solution:
package chess;
import java.awt.*;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
/**
* Board.java
* Purpose: This will set up the Board for the game to be played,
* ,passed by the Game.java, like setting up appropriate board style, setting
* pieces in correct place and style according to colour chosen by Player etc,
* Also Board class shares calling classes instance as the calling class has the
* necessary methods needed to check if the player move is acceptable, and
* enforce rules etc on actions like moving a piece from one block to another
*
*
* @author David Kroukamp
* @version 1.0 3/11/2012
*/
public class Board extends Main {
private Image boardImage1;
private Image boardImage2;
private JPanel centerPanel = new JPanel();
private JPanel southPanel = new JPanel();
private JPanel eastPanel = new JPanel();
private JPanel westPanel = new JPanel();
private JLabel[] labels = new JLabel[64];
private ImagePanel[] panels = new ImagePanel[64];
public Board(Image boardImage1, Image boardImage2) {
this.boardImage1 = boardImage1;
this.boardImage2 = boardImage2;
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
createAndShowGUI();
}
});
}
/**
* Create the GUI and show it; for thread safety, this method should be
* invoked from the event-dispatching thread.
*/
private void createAndShowGUI() {
//Create and set up the window with title.APP_NAME + " " + VERSION_ID + " by " + AUTHOR
setTitle(APP_NAME + " " + VERSION_ID + " by " + AUTHOR);
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
//Set up the content pane.
addComponentsToPane(getContentPane());
//Size and display the window.
setSize(800, 600);
//center JFrame.
setLocationRelativeTo(null);
//makes frame non-resizable
setResizable(false);
//shows the frame
setVisible(true);
}
/**
* Adds all the necessary components to the content pane of the JFrame, and
* adds appropriate listeners to components.
*/
private void addComponentsToPane(Container contentPane) {
BorderLayout borderLayout = new BorderLayout(10, 10);
GridLayout gridLayout = new GridLayout(8, 8);
contentPane.setLayout(borderLayout);
centerPanel.setLayout(gridLayout);
addLabelsToSouthPanel();
addLabelsToWestPanel();
addPanelsAndLabels();
contentPane.add(centerPanel, BorderLayout.CENTER);
contentPane.add(southPanel, BorderLayout.SOUTH);
contentPane.add(eastPanel, BorderLayout.EAST);
contentPane.add(westPanel, BorderLayout.WEST);
listLabelNames//works when i call from here prints fine
}
private void addLabelsToSouthPanel() {
GridLayout gridLayout = new GridLayout(0, 8);
southPanel.setLayout(gridLayout);
JLabel[] lbls = new JLabel[8];
String[] label = {"A", "B", "C", "D", "E", "F", "G", "H"};
for (int i = 0; i < 8; i++) {
lbls[i] = new JLabel(label[i] + "");
southPanel.add(lbls[i]);
}
}
private void addLabelsToWestPanel() {
GridLayout gridLayout = new GridLayout(8, 0);
westPanel.setLayout(gridLayout);
JLabel[] lbls = new JLabel[8];
int[] num = {8, 7, 6, 5, 4, 3, 2, 1};
for (int i = 0; i < 8; i++) {
lbls[i] = new JLabel(num[i] + "");
westPanel.add(lbls[i]);
}
}
private void addPanelsAndLabels() {
addPanelsAndImages();
for (int i = 0; i < panels.length; i++) {
labels[i] = new JLabel();
labels[i].setName(panels[i].getName());//used to know the postion of the label on the board
panels[i].add(labels[i]);
centerPanel.add(panels[i]);
//System.out.println(panels[i].getName());//works when i call from here prints fine
//System.out.println(labels[i].getName());//works when i call from here prints fine
System.out.println("done");
}
}
private void addPanelsAndImages() {
int count = 0;
String[] label = {"A", "B", "C", "D", "E", "F", "G", "H"};
int[] num = {8, 7, 6, 5, 4, 3, 2, 1};
for (int row = 0; row < 8; row++) {
for (int col = 0; col < 8; col++) {
if (row % 2 == 0) {
if ((col + row) % 2 == 0) {
panels[count] = new ImagePanel(boardImage1);
} else {
panels[count] = new ImagePanel(boardImage2);
}
} else {
if ((col + row) % 2 == 0) {
panels[count] = new ImagePanel(boardImage1);
} else {
panels[count] = new ImagePanel(boardImage2);
}
}
panels[count].setName(label[col] + " " + num[row]);
count++;
}
}
}
//method sets image of a label at a certain position in the board according to the block name i.e D4
public void listLabelNames() {
for (int s = 0; s < labels.length; s++) {
System.out.println(labels[s].getName());
}
}
//nested class used to set the background of frame contenPane
class ImagePanel extends JPanel {
private Image image;
/**
* Default constructor used to set the image for the background for the
* instance
*/
public ImagePanel(Image img) {
image = img;
}
@Override
protected void paintComponent(Graphics g) {
//draws image to background to scale of frame
g.drawImage(image, 0, 0, null);
}
}
}
and in the calling class i call board like this:
public void startGame() {
Image boardImage1 = new ImageIcon(boardImages + "wBlock.jpg").getImage();
Image boardImage2 = new ImageIcon(boardImages + "bBlock.jpg").getImage();
Board board = new Board(boardImage1, boardImage2);
board.listLabelNames();//returns null pointer here but not when called from within the instance
/*
while(checkmate!=true||stalemate!=true||surrender!=true) {
}
*/
}
