Lesson Six - ClearableScribble
This applet is borrowed from Java in a Nutshell. It is a subclass of the ColorScribble in lesson Five.
In addition to the stuff inherited from ColorScribble,
ClearableScribble adds a button that clears the window when clicked.
The APPLET Tag
The HTML Appplet tag is:
<APPLET code="ClearableScribble.class" width=300 height=300>
<PARAM name="foreground" value="0000FF">
<PARAM name="background" value="FFCCCC">
</APPLET>
Program Listing
The java program is:
// This example is from the book _Java in a Nutshell_ by David Flanagan.
// Written by David Flanagan. Copyright (c) 1996 O'Reilly & Associates.
// You may study, use, modify, and distribute this example for any purpose.
// This example is provided WITHOUT WARRANTY either expressed or implied.
import java.applet.*;
import java.awt.*;
public class ClearableScribble extends ColorScribble {
private Button clear_button;
public void init() {
// do ColorScribble initialization first
super.init();
// Create a button and add it to the applet.
clear_button = new Button("Clear");
clear_button.setForeground(Color.black);
clear_button.setBackground(Color.lightGray);
this.add(clear_button);
}
public boolean action(Event event, Object arg) {
// If our button was clicked on, handle it.
// Otherwise, let our superclass handle it if it wants to.
if (event.target == clear_button) {
Graphics g = this.getGraphics();
Rectangle r = this.bounds();
g.setColor(this.getBackground());
g.fillRect(r.x, r.y, r.width, r.height);
g.setColor(this.getForeground());
return true;
}
else return super.action(event, arg);
}
}