Canvas

A Canvas is a generic graphical component representing a region where you can draw things such as rectangles, circles, and text strings. For example, when writing a drawing applet, the region where objects are drawn would a subclass of Canvas.

Corresponding source code:

import java.applet.*;
import java.awt.*;
public class CanvasWidget extends Applet {
    public void init()
    {
        DrawingRegion region = new DrawingRegion(100,50);
        add(region);
    }
}

class DrawingRegion extends Canvas {
    int w,h;
    public DrawingRegion(int ww, int hh) {
        w=ww;
        h=hh;
        resize(w,h);
    }
    public void paint(Graphics g)
    {
        g.drawRect(0,0,w-1,h-1); // draw border
        g.drawString("A Canvas", 20,20);
    }
}

Method(s) of note:

• public void paint(Graphics g)
  You normally subclass Canvas to override the default Canvas paint method.

The normal event convenience methods are also often overridden in Canvas subclasses such as mouseDown and mouseDrag.

Related Magercise(s):

• ColorTest