Question

I am programming a chess game in java, and at the moment I am building a basic interface. It is simply an 8×8 array of buttons that will display in a window. I have coded for these buttons, and have gotten the board to display properly. However, when I connect this with the rest of the game, the game window crashes upon running and I have to force quit the java application. This is my code:

package Chess_Game; 
import javax.swing.SwingUtilities;
import Chess_Interface.Iboard;

public class Game_Tester 
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable() 
        {
            public void run() 
            {
                    Game G = new Game();
                    Iboard I = new Iboard(G.getBoard().getArray(), G.getSides());
                    I.setVisible(true);
                    while(!(G.isGameOver()))
                    {
                        boolean redo = true;
                        while(redo)
                        {
                            int row = 0; 
                            int col = 0; 
                            int nRow = 0; 
                            int nCol = 0;
                            System.out.println("Click the piece you want to move.");
                            while(!(I.getBool())){}
                            if(I.getBool())
                            {
                                row = I.getRow();
                                col = I.getCol();
                                I.setBool(false);
                            }
                            System.out.println("Click the place you want to move to.");
                            while(!(I.getBool())){}
                            if(I.getBool())
                            {
                                nRow = I.getRow();
                                nCol = I.getCol();
                                I.setBool(false);
                            }
                            if(G.canMove(row, col, nRow, nCol))
                            {
                                G.move(row, col, nRow, nCol, I);
                                redo = false;
                            }
                            else
                            {
                                System.out.println("You cant move there! Try again!");
                            }
                        }
                        I.updateBoard(G.getBoard().getArray(), G.getSides());
                    }
            }
        });
    }
}

The board displays properly when I comment out the main while loop (and everything inside of it), and I assume the problem lies somewhere inside there, but I have been unable to find it. I have also looked online for similar game loop problems, but all of those have been for games involving frame rates and movement across a java swing frame, something that is not present in my code.

Any help would be greatly appreciated.

Answer 1

You have several loops such as

while(!(I.getBool())){}

which could potentially run forever if I does not respond as expected. You could start by printing something out within these loops, and within the following blocks if(I.getBool()){...} to see at what point your application gets stuck.

Checking the user interface in a loop like this is not good practice. It is better to use Listeners to respond to the user interface.

Nor is running the main application on the Swing thread using SwingUtilities.invokeLater(new Runnable(), even though it avoids potential problems of updating the GUI from another thread.

In fact, this may be your root problem, as running the main application loop on the Swing thread (the thread used to run the GUI) like this probably prevents the GUI from ever responding properly. You are putting a task (the entire game) onto the GUI’s queue, but that task never completes while(!(G.isGameOver())).