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AWT Canvas Class

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Canvas Class

Introduction

Canvas class control represents a rectangular area where the application can draw something or can receive inputs created by the user.

Class declaration

Following is the declaration for java.awt.Canvas class:

public class Canvas
   extends Component
      implements Accessible

Class constructors

S.N.Constructor & Description
1Canvas()Constructs a new Canvas.
2Canvas(GraphicsConfiguration config)Constructs a new Canvas given a GraphicsConfiguration object.

Class methods

S.N.Method & Description
1void addNotify()Creates the peer of the canvas.
2void createBufferStrategy(int numBuffers)Creates a new strategy for multi-buffering on this component.
3void createBufferStrategy(int numBuffers, BufferCapabilities caps)Creates a new strategy for multi-buffering on this component with the required buffer capabilities.
4AccessibleContext getAccessibleContext()Gets the AccessibleContext associated with this Canvas.
5BufferStrategy getBufferStrategy()Returns the BufferStrategy used by this component.
6void paint(Graphics g)Paints this canvas.
7void pdate(Graphics g)Updates this canvas.

Methods inherited

This class inherits methods from the following classes:

  • java.awt.Component
  • java.lang.Object

Canvas Example

Create the following java program using any editor of your choice in say D:/ > AWT > com > adglob > gui >AwtControlDemo.java

package com.adglob.gui;

import java.awt.*;
import java.awt.event.*;

public class AwtControlDemo {

   private Frame mainFrame;
   private Label headerLabel;
   private Label statusLabel;
   private Panel controlPanel;

   public AwtControlDemo(){
      prepareGUI();
   }

   public static void main(String[] args){
      AwtControlDemo  awtControlDemo = new AwtControlDemo();
      awtControlDemo.showCanvasDemo();
   }

   private void prepareGUI(){
      mainFrame = new Frame("Java AWT Examples");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
         }        
      });    
      headerLabel = new Label();
      headerLabel.setAlignment(Label.CENTER);
      statusLabel = new Label();        
      statusLabel.setAlignment(Label.CENTER);
      statusLabel.setSize(350,100);

      controlPanel = new Panel();
      controlPanel.setLayout(new FlowLayout());

      mainFrame.add(headerLabel);
      mainFrame.add(controlPanel);
      mainFrame.add(statusLabel);
      mainFrame.setVisible(true);  
   }

   private void showCanvasDemo(){
      headerLabel.setText("Control in action: Canvas"); 

      controlPanel.add(new MyCanvas());
      mainFrame.setVisible(true);  
   } 

   class MyCanvas extends Canvas {

      public MyCanvas () {
         setBackground (Color.GRAY);
         setSize(300, 300);
      }

      public void paint (Graphics g) {
         Graphics2D g2;
         g2 = (Graphics2D) g;
         g2.drawString ("It is a custom canvas area", 70, 70);
      }
   }
}

Compile the program using command prompt. Go to D:/ > AWT and type the following command.

D:\AWT>javac com\adglob\gui\AwtControlDemo.java

If no error comes that means compilation is successful. Run the program using following command.

D:\AWT>java com.adglob.gui.AwtControlDemo

Verify the following output

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