Java AWT | Canvas Class

Canvas class is a part of Java AWT. Canvas is a blank rectangular area where the user can draw or trap input from the user. Canvas class inherits the Component class.

Constructor of the Canvas class are :

  1. Canvas(): Creates a new blank canvas.
  2. Canvas(GraphicsConfiguration c): Creates a new canvas with a specified graphics configuration.

Commonly used Methods in Canvas Class



Method Explanation
addNotify() Creates the peer of the canvas.
createBufferStrategy(int n) Creates a new strategy for multi-buffering on this component.
createBufferStrategy(int n, BufferCapabilities c) Creates a new strategy for multi-buffering on this component with the required buffer capabilities
getBufferStrategy() Returns the BufferStrategy used by this component.
paint(Graphics g) paints this component.
update(Graphics g) updates this canvas.

Below programs illustrate the use of Canvas Class :

  • Program 1: To create a canvas and paint the canvas.

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    // Java Program to create a to create
    // a canvas and paint the canvas
    import java.awt.*;
    import javax.swing.*;
    class canvas extends JFrame {
      
        // constuctor
        canvas()
        {
            super("canvas");
      
            // create a empty canvas
            Canvas c = new Canvas() {
      
                // paint the canvas
                public void paint(Graphics g)
                {
                    // set color to red
                    g.setColor(Color.red);
      
                    // set Font
                    g.setFont(new Font("Bold", 1, 20));
      
                    // draw a string
                    g.drawString("This is a canvas", 100, 100);
                }
            };
      
            // set background
            c.setBackground(Color.black);
      
            add(c);
            setSize(400, 300);
            show();
        }
      
        // Main Method
        public static void main(String args[])
        {
            canvas c = new canvas();
        }
    }

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    Output:

  • Program 2: To create a canvas and add mouse listener to the canvas(a circle of radius 5 will appear at the points where mouse are clicked or dragged on the canvas).
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    // Java Program to create a to create a 
    // canvas and mouse listener to the 
    // canvas ( a circle of radius 5 will appear
    // at the points where mouse are clicked or
    //  dragged on the canvas)
    import java.awt.*;
    import javax.swing.*;
    import java.awt.event.*;
      
    class canvas extends JFrame implements MouseListener, MouseMotionListener {
      
        // create a canvas
        Canvas c;
      
        // constuctor
        canvas()
        {
            super("canvas");
      
            // create a empty canvas
            c = new Canvas() {
                public void paint(Graphics g)
                {
                }
            };
      
            // set background
            c.setBackground(Color.black);
      
            // add mouse listener
            c.addMouseListener(this);
            c.addMouseMotionListener(this);
      
            add(c);
            setSize(400, 300);
            show();
        }
      
        // mouse listener  and mouse motion listener mehods
        public void mouseClicked(MouseEvent e)
        {
            Graphics g = c.getGraphics();
      
            g.setColor(Color.red);
      
            // get X and y position
            int x, y;
            x = e.getX();
            y = e.getY();
      
            // draw a Oval at the point 
            // where mouse is moved
            g.fillOval(x, y, 5, 5);
        }
      
        public void mouseMoved(MouseEvent e)
        {
        }
      
        public void mouseDragged(MouseEvent e)
        {
            Graphics g = c.getGraphics();
      
            g.setColor(Color.red);
      
            // get X and y position
            int x, y;
            x = e.getX();
            y = e.getY();
      
            // draw a Oval at the point where mouse is moved
            g.fillOval(x, y, 5, 5);
        }
      
        public void mouseExited(MouseEvent e)
        {
        }
      
        public void mouseEntered(MouseEvent e)
        {
        }
      
        public void mouseReleased(MouseEvent e)
        {
        }
      
        public void mousePressed(MouseEvent e)
        {
        }
        // main class
        public static void main(String args[])
        {
            canvas c = new canvas();
        }
    }

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    Output:

Reference: https://docs.oracle.com/javase/7/docs/api/java/awt/Canvas.html



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