Question

I’m making a drawing board, and I have a few questions.

1. Whenever I try to draw on it, it doesn’t automatically update. Ad I usually have to resize the screen for it to update.
2. How can I do something like a mouseDragged function, in which i can continually get the x and y coords?

Here is the code:

import java.awt.geom.*;
class griddedInput extends JComponent implements MouseListener
{
    int SIZE = 10;
    int scSize = 300;
    int sSize = scSize/SIZE;
    boolean [][] grid = new boolean[sSize][sSize];
    public griddedInput(boolean grid[][])
    {
        grid=grid;
        setPreferredSize(new Dimension(scSize,scSize));
        addMouseListener(this);
    }
    public void paintComponent(Graphics g)
    {
        Graphics2D g2 = (Graphics2D) g;
        int x, y;
        for(y = 0; y < sSize; y ++) {
            for(x = 0; x < sSize; x ++) {
                if(grid[y][x])
                    g2.setColor(Color.BLACK);
                else
                    g2.setColor(Color.WHITE);
                g2.fillRect((x * SIZE), (y * SIZE), sSize, sSize);
            }
        }
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        int squareX = (int)e.getX() / SIZE;
        int squareY = (int)e.getY() / SIZE;
        grid[squareY][squareX] = !grid[squareY][squareX];
    }

    @Override
    public void mouseEntered(MouseEvent e) {
        // TODO Auto-generated method stub      
    }

    @Override
    public void mouseExited(MouseEvent e) {
        // TODO Auto-generated method stub
    }

    @Override
    public void mousePressed(MouseEvent e) {
        // TODO Auto-generated method stub
    }

    @Override
    public void mouseReleased(MouseEvent e) {
        // TODO Auto-generated method stub
    }
}

Answer 1

You’ll want to call repaint() on the drawing component any time you want to suggest to the JVM that it be painted — most likely in your MouseListener method(s).

e.g.,

@Override
public void mouseClicked(MouseEvent e) {
    int squareX = (int)e.getX() / SIZE;
    int squareY = (int)e.getY() / SIZE;
    grid[squareY][squareX] = !grid[squareY][squareX];
    repaint();
}

To speed up repainting, you can also call the overload method that allows you to repaint a select rectangle of your GUI, but I’ll bet that you don’t need to do that for this GUI.

You’ll also want to be a little less “creative” with your code indentation if you want others to better be able to understand it and help you.

Edit
Regarding:

2.How can I do something like a mouseDragged function, in which i can continually get the x and y coords?

Also add a MouseMotionListener. It can be the same class, and in fact usually I use an anonymous inner class for this, one that extends MouseAdapter, and one whose single instance I use for both MouseListener and MouseMotionListener. I have examples of using this in several posts in this very forum.