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Graphics Methods in Java

Discussion in 'Java' started by pradeep, Nov 3, 2006.

  1. pradeep

    pradeep Team Leader

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    Drawing Lines



    The drawLine method belongs to the Graphics class.

    This example draws a fan of twenty lines from the bottom center of the Applet along the top edge. The applet's getSize method is used to find the dimensions of the applet.
    Code:
    import java.awt.*;
    import java.applet.*;
    public class LineExample extends Applet
    {
        public LineExample()
        {
            this.setBackground(new Color(255, 255, 255));
            this.setForeground(new Color(255, 0, 0));
        }
        public void paint(Graphics g)
        {
            // Get the width and height of the Applet
            int width = this.getSize().width;
            int height = this.getSize().height;
            // Fan 20 lines from the bottom-middle, across the top
            for (int counter=0; counter<=width; counter+=(width/20))
                g.drawLine(width/2, height, counter, 0);
        }
    }

    Drawing Ovals



    The drawOval method belongs to the Graphics class.

    The drawOval method takes four parameters; x, y, width, and height. The following example draws an oval, half the size of the applet, in the center of the applet.
    Code:
    import java.awt.*;
    import java.applet.*;
    public class OvalExample extends Applet
    {
        public OvalExample()
        {
            this.setBackground(new Color(255, 255, 255));
            this.setForeground(new Color(255, 0, 0));
        }
        public void paint(Graphics g)
        {
            // Get the width and height of the Applet
            int width = this.getSize().width;
            int height = this.getSize().height;
            g.drawOval(width/4, height/4, width/2, height/2);
        }
    }

    Freehand Drawing



    In the previous examples, the paint method was used to display graphics on the applet. The paint method has a parameter for the graphics context, but you may wish to use the graphics context in other methods that don't have a graphics parameter. The getGraphics method is used to return the graphics context for a component, which in this case is the applet.

    Graphics g = this.getGraphics();

    Freehand Example:



    The following example uses the getGraphics method for free-hand drawing. The example uses a MouseListener, and a MouseMotionListener, which are part of the Java 1.1 Event Model.
    Code:
    import java.awt.*;
    import java.applet.*;
    import java.awt.event.*;
    public class FreehandExample extends Applet implements MouseListener, MouseMotionListener
    {
        private Point start, end;
        public FreehandExample()
        {
            this.setBackground(new Color(255, 204, 0));
            this.setForeground(new Color(51, 153, 204));
            // Add the Event Listeners
            this.addMouseListener(this);
            this.addMouseMotionListener(this);
        }
        // Capture the mousePressed event
        public void mousePressed(MouseEvent e)
        {
            start = new Point(e.getX(), e.getY());
        }
        // Define the other events for MouseListener
        public void mouseClicked(MouseEvent e) {}
        public void mouseEntered(MouseEvent e) {}
        public void mouseExited(MouseEvent e) {}
        public void mouseReleased(MouseEvent e) {}
    	
        // Capture the mouseDrag event
        public void mouseDragged(MouseEvent e)
        {
            // Get the current state of the graphics
            Graphics g = this.getGraphics();
    		
            end = new Point(e.getX(), e.getY());
            g.drawLine(start.x, start.y, end.x, end.y);
            start = end;
        }
        // Define the other events for MouseMotionListener
        public void mouseMoved(MouseEvent e) {}
    }
     

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