Question

I’m having some trouble getting a JButton to update repeatedly (used with a timer) in a do-while loop. I’m working on a simple game, played on a 10 * 10 grid of tile objects which correspond to a JButton arrayList with 100 buttons.

This part of the program handles simple pathfinding (i.e. if I click on character, then an empty tile, the character will move through each tile on its way to the destination). There is a delay between each step so the user can see the character’s progress.

In the current state of things, the movement is correct, but the JButton is only updated when the character reaches the destination, not on intermediate steps.

public void move(int terrainTile)
{
    int currentPosition = actorList.get(selectedActor).getPosition();
    int movementValue = 0;
    int destination = terrainTile;
    int destinationX = destination / 10;
    int destinationY = destination % 10;

    do
    {
        currentPosition = actorList.get(selectedActor).getPosition();  // Gets PC's current position (before move)
        System.out.println("Old position is " + currentPosition);
        int currentX = currentPosition / 10;
        int currentY = currentPosition % 10;


        if(actorList.get(selectedActor).getCurrentAP() > 0)
        {
            movementValue = 0;

            if(destinationX > currentX)
            {
                movementValue += 10;
            }

            if(destinationX < currentX)
            {
                movementValue -= 10;
            }

            if(destinationY > currentY)
            {
                movementValue += 1;
            }

            if(destinationY < currentY)
            {
                movementValue -= 1;
            }

            int nextStep = currentPosition + movementValue;

            myGame.setActorIdInTile(currentPosition, -1);  //Changes ActorId in PC current tile back to -1
            scrubTiles(currentPosition);

            actorList.get(selectedActor).setPosition(nextStep);  //  Sets new position in actor object
            System.out.println("Actor " + selectedActor + " " + actorList.get(selectedActor).getName() + " position has been updated to " + nextStep);

            myGame.setActorIdInTile(nextStep, selectedActor); // Sets ActorId in moved to Tile
            System.out.println("Tile " + nextStep + " actorId has been updated to " + selectedActor);

            buttons.get(nextStep).setIcon(new ImageIcon(actorList.get(selectedActor).getImageName()));

            // If orthagonal move AP-4
            if(movementValue == 10 || movementValue == -10 || movementValue == 1 || movementValue == -1)
            {
                actorList.get(selectedActor).reduceAP(4);
            }
            // If diagonal move AP-6
            else
            {
                actorList.get(selectedActor).reduceAP(6);
            }

            System.out.println(actorList.get(selectedActor).getName() + " has " + actorList.get(selectedActor).getCurrentAP() + " AP remaining");

            try
            {
                Thread.sleep(500);    // one second
            }
            catch (Exception e){} 

            buttons.get(nextStep).repaint();

        }

        else
        {
            System.out.println(actorList.get(selectedActor).getName() + " has insufficient AP to move");
            break;
        }

    }while(destination != (currentPosition + movementValue));

What I’ve tried:

1. buttons.get(nextStep).repaint(); (Tried putting a command to repaint the button after setting the imageIcon. No change.

2. buttons.get(nextStep).revalidate(); (No 100% sure what this does – it came up as a potential solution, but doesn’t work.

3. Steps 1 & 2 combined

4. Looked into the swing timer class – movement doesn’t occur everytime an actionEvent is fired, (only if character is selected and target tile is empty) so not sure how I could get this to work

Any help would be greatly appreciated!

Answer 1

I really dont’ know exactly what you wanted to know in your comments, though +1 to the answer above, seems to me that’s the real cause. Have a look at this example program, simply add your call to the move(...) method inside the timerAction, seems like that can work for you. Here try this code :

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class GridExample
{
    private static final int SIZE = 36;
    private JButton[] buttons;
    private int presentPos;
    private int desiredPos;
    private Timer timer;
    private Icon infoIcon = 
                UIManager.getIcon("OptionPane.informationIcon");

    private ActionListener timerAction = new ActionListener()
    {
        public void actionPerformed(ActionEvent ae)
        {
            buttons[presentPos].setIcon(null);
            if (desiredPos < presentPos)
            {
                presentPos--;
                buttons[presentPos].setIcon(infoIcon);
            }
            else if (desiredPos > presentPos)
            {
                presentPos++;
                buttons[presentPos].setIcon(infoIcon);
            }
            else if (desiredPos == presentPos)
            {
                timer.stop();
                buttons[presentPos].setIcon(infoIcon);
            }
        }
    };

    public GridExample()
    {
        buttons = new JButton[SIZE];
        presentPos = 0;
        desiredPos = 0;
    }

    private void createAndDisplayGUI()
    {
        JFrame frame = new JFrame("Grid Game");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel contentPane = new JPanel();
        contentPane.setLayout(new GridLayout(6, 6, 5, 5));
        for (int i = 0; i < SIZE; i++)
        {
            final int counter = i;
            buttons[i] = new JButton();
            buttons[i].setActionCommand("" + i);
            buttons[i].addActionListener(new ActionListener()
            {
                public void actionPerformed(ActionEvent ae)
                {
                    desiredPos = Integer.parseInt(
                                    (String) buttons[counter].getActionCommand());
                    timer.start();              
                }
            });
            contentPane.add(buttons[i]);
        }
        buttons[presentPos].setIcon(infoIcon);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
        timer = new Timer(1000, timerAction);
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                new GridExample().createAndDisplayGUI();
            }
        });
    }
}