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 :
- Canvas(): Creates a new blank canvas.
- 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.
Java
// Java Program to create a to create// a canvas and paint the canvasimport java.awt.*;import javax.swing.*;class canvas extends JFrame { // constructor 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(); }} |
- 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).
Java
// Java Program 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; // constructor 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 methods 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(); }} |
- Output:
Reference: https://docs.oracle.com/javase/7/docs/api/java/awt/Canvas.html
