A simple drawing program.

this is a simple drawing program. Should already be commented appropriately.

Code:

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import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

/**
 * YEAH!
 */
public class DrawingProgram extends Applet
implements MouseListener, MouseMotionListener {

    private static final int
    BLACK = 0,
    RED = 1,            // Some constants to make
    GREEN = 2,          // the code more readable.
    BLUE = 3,          // These numbers code for
    CYAN = 4,          // the differnet drawing colors.
    MAGENTA = 5,
    YELLOW = 6;

    private static final int PALETTE_WIDTH = 56;
    private static final int WHITE_AREA = 50;
    private static final int BORDER_WIDTH = 3;

    private int currentColour = BLACK;  // The currently selected drawing color,
    //  coded as one of the above constants.


    private int prevX, prevY;    // The previous location of the mouse.

    private boolean isDragging;      // This is set to true while the user is drawing.

    private Graphics graphicsContext;  // A graphics context for the applet
    // that is used to draw the user's curve.

    /**
    * Add listeners to the applet.
    */
    public void init() {
        addMouseListener(this);
        addMouseMotionListener(this);
    }

    /**
    * Overriding update so that it doesn't fill the applet with
    * bg colour when callin paint()
    * @see java.awt.Container#update(java.awt.Graphics)
    */
    public void update(Graphics g) {
        paint(g);
    }


    /**
    * Overriding paint method; draws contents of the applet.
    * @see java.awt.Container#paint(java.awt.Graphics)
    */
    public void paint(Graphics g) {

        int width = getSize().width;    // Width of the applet.
        int height = getSize().height;  // Height of the applet.

        // Distance between the top of one colored rectangle in the palette
        // and the top of the rectangle below it.
        int colourSpacing = (height - PALETTE_WIDTH) / 7;

        // fill the drawing area.
        g.setColor(Color.white);
        g.fillRect(BORDER_WIDTH, BORDER_WIDTH, width - 59, height - 6);

        //draw the border.
        g.setColor(Color.gray);
        g.drawRect(0, 0, width-1, height-1);
        g.drawRect(1, 1, width-BORDER_WIDTH, height-BORDER_WIDTH);
        g.drawRect(2, 2, width-5, height-5);

        //draw the colour palette
        g.fillRect(width - PALETTE_WIDTH, 0, PALETTE_WIDTH, height);

        //draw the clear button
        g.setColor(Color.white);
        g.fillRect(width-53,  height-53, WHITE_AREA, WHITE_AREA);
        g.setColor(Color.black);
        g.drawRect(width-53, height-53, 49, 49);
        g.drawString("CLEAR", width-48, height-23);

        //draw the colour swatches
        g.setColor(Color.black);
        g.fillRect(width-53, BORDER_WIDTH + 0*colourSpacing,
                  WHITE_AREA, colourSpacing-BORDER_WIDTH);
        g.setColor(Color.red);
        g.fillRect(width-53, BORDER_WIDTH + 1*colourSpacing,
                  WHITE_AREA, colourSpacing-BORDER_WIDTH);
        g.setColor(Color.green);
        g.fillRect(width-53, BORDER_WIDTH + 2*colourSpacing,
                  WHITE_AREA, colourSpacing-BORDER_WIDTH);
        g.setColor(Color.blue);
        g.fillRect(width-53, BORDER_WIDTH + BORDER_WIDTH*colourSpacing,
                  WHITE_AREA, colourSpacing-BORDER_WIDTH);
        g.setColor(Color.cyan);
        g.fillRect(width-53, BORDER_WIDTH + 4*colourSpacing,
                  WHITE_AREA, colourSpacing-BORDER_WIDTH);
        g.setColor(Color.magenta);
        g.fillRect(width-53, BORDER_WIDTH + 5*colourSpacing,
                  WHITE_AREA, colourSpacing-BORDER_WIDTH);
        g.setColor(Color.yellow);
        g.fillRect(width-53, BORDER_WIDTH + 6*colourSpacing,
                  WHITE_AREA, colourSpacing-BORDER_WIDTH);

        //draw colour highlight
        g.setColor(Color.white);
        g.drawRect(width-55, 1 + currentColour*colourSpacing, 53, colourSpacing);
        g.drawRect(width-54, 2 + currentColour*colourSpacing, 51, colourSpacing-2);

    }



    /**
    * Change the drawing colour after the user has clicked the mouse
    * on the colour palette.
    * @param y
    */
    private void changeColor(int y) {

        int width = getSize().width;          // Width of applet.
        int height = getSize().height;        // Height of applet.
        int colorSpacing = (height - PALETTE_WIDTH) / 7;  // Space for one color rectangle.
        int newColor = y / colorSpacing;      // Which color number was clicked?

        if (newColor < 0 || newColor > 6)      // Make sure the color number is valid.
            return;

        /* Remove the hilite from the current color, by drawing over it in gray.
        Then change the current drawing color and draw a hilite around the
        new drawing color.  */

        Graphics g = getGraphics();
        g.setColor(Color.gray);
        g.drawRect(width-55, 1 + currentColour*colorSpacing, 53, colorSpacing);
        g.drawRect(width-54, 2 + currentColour*colorSpacing, 51, colorSpacing-2);
        currentColour = newColor;
        g.setColor(Color.white);
        g.drawRect(width-55, 1 + currentColour*colorSpacing, 53, colorSpacing);
        g.drawRect(width-54, 2 + currentColour*colorSpacing, 51, colorSpacing-2);
        g.dispose();

    }


    /**
    * Set the colour of the current sketch.
    */
    private void setUpDrawingGraphics() {
        graphicsContext = getGraphics();
        switch (currentColour) {
            case BLACK:
                graphicsContext.setColor(Color.black);
                break;
            case RED:
                graphicsContext.setColor(Color.red);
                break;
            case GREEN:
                graphicsContext.setColor(Color.green);
                break;
            case BLUE:
                graphicsContext.setColor(Color.blue);
                break;
            case CYAN:
                graphicsContext.setColor(Color.cyan);
                break;
            case MAGENTA:
                graphicsContext.setColor(Color.magenta);
                break;
            case YELLOW:
                graphicsContext.setColor(Color.yellow);
                break;
        }
    }

    /**
    * Called when the user presses the button anywhere.
    * @see java.awt.event.MouseListener#mousePressed(java.awt.event.MouseEvent)
    */
    public void mousePressed(MouseEvent evt) {

        int x = evt.getX();  // x-coordinate where the user clicked.
        int y = evt.getY();  // y-coordinate where the user clicked.

        int width = getSize().width;    // Width of the applet.
        int height = getSize().height;  // Height of the applet.

        //do nothing if already drawing.
        if (isDragging == true)
            return;         

        if (x > width - 53) {

            //selects the colour palette.
            if (y > height - 53)
                repaint();      //  Clicked on "CLEAR button".
            else
                changeColor(y);  // Clicked on the color palette.
        }
        else if (x > BORDER_WIDTH && x < width - PALETTE_WIDTH && y > BORDER_WIDTH && y < height - BORDER_WIDTH) {
            // The user has clicked on the white drawing area.
            // Start drawing a curve from the point (x,y).
            prevX = x;
            prevY = y;
            isDragging = true;
            setUpDrawingGraphics();
        }

    }

    /**
    * Called whenever the user releases the mouse button.
    * @see java.awt.event.MouseListener#mouseReleased(java.awt.event.MouseEvent)
    */
    public void mouseReleased(MouseEvent evt) {
        // Nothing to do because the user isn't drawing.
        if (isDragging == false)
            return;  // Nothing to do because the user isn't drawing.
        isDragging = false;
        graphicsContext.dispose();
        graphicsContext = null;
    }


    /**
    * Called whenever the user moves the mouse
    * @see java.awt.event.MouseMotionListener#mouseDragged(java.awt.event.MouseEvent)
    */
    public void mouseDragged(MouseEvent evt) {

        if (isDragging == false)
            return;  // Nothing to do because the user isn't drawing.

        int x = evt.getX();  // x-coordinate of mouse.
        int y = evt.getY();  // y=coordinate of mouse.

        if (x < BORDER_WIDTH)                          // Adjust the value of x,
            x = BORDER_WIDTH;                          //  to make sure it's in
        if (x > getSize().width - 57)      //  the drawing area.
            x = getSize().width - 57;

        if (y < BORDER_WIDTH)                          // Adjust the value of y,
            y = BORDER_WIDTH;                          //  to make sure it's in
        if (y > getSize().height - 4)      //  the drawing area.
            y = getSize().height - 4;

        graphicsContext.drawLine(prevX, prevY, x, y);  // Draw the line.

        prevX = x;  // Get ready for the next line segment in the curve.
        prevY = y;

    }

    // implementing the MouseListener interface requires us to
    // define these methods, even if we never use them.
    public void mouseEntered(MouseEvent evt) { } 
    public void mouseExited(MouseEvent evt) { }     
    public void mouseClicked(MouseEvent evt) { } 
    public void mouseMoved(MouseEvent evt) { }   
}

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Damn derek nice work. You code this is your spare time?

No this was for a first year course at school. I wouldn't code Java in my spare time haha. I'm not a fan of it.

not to bring up an old thread or anything..but uhh..what's it do?

Quote:

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Originally Posted by Papa

not to bring up an old thread or anything..but uhh..what's it do?

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A basic drawing program like paint :)