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 Program to create a to create
// a canvas and paint the canvas
import 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 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();
}
}
