/*
Applet displays a colored dot with randomly selected colors and
animates the dot to pop up at random places on the screen in
the applet area.
*/
import java.awt.*;
import java.applet.*;
import java.lang.Math;
public class coloredDot extends Applet implements Runnable {
TextField dotSizeField;
Thread runner;
Button startStop;
boolean isRunning = true;
// diameter d of dot, which is both its width and height
int d = 20;
int newSize = -1;
// x and y of the dot's position
int x = (int)this.size().width/2;
int y = (int)this.size().height/2;
// array of RGB values of dot's color
int[] dot = {0, 0, 0};
public void init() {
setBackground(Color.white);
this.setLayout(new FlowLayout(FlowLayout.CENTER, 15, 4));
startStop = new Button("Stop");
add(startStop);
add (new Label("Size of Dot in Pixels:"));
dotSizeField = new TextField(2);
add(dotSizeField);
}
public void start() {
if (runner == null) {
runner = new Thread(this);
runner.start();
}
}
public void stop() {
runner = null;
}
public void run() {
while (isRunning) {
try {
Thread.sleep(1000);
}
catch (InterruptedException e) {
}
repaint();
}
}
public void paint(Graphics g) {
if (isRunning) {
g.setColor(Color.white);
g.fillRect(0, 0, this.size().width, this.size().height);
g.setColor(Color.black);
if (this.newSize == -1) {
g.drawString("Enter a number", 320, 40);
}
else {
this.d = this.newSize;
}
g.setColor(new Color(dot[0], dot[1], dot[2]));
g.fillOval(x, y, d, d);
this.x = (int)(Math.random()*this.size().width);
this.y = (int)(Math.random()*this.size().height-24);
this.dot[0] = (int)(Math.random()*255);
this.dot[1] = (int)(Math.random()*255);
this.dot[2] = (int)(Math.random()*255);
} // end of if isRunning
}
public final void update(Graphics g) {
paint(g);
}
public boolean action(Event e, Object arg) {
if (e.target instanceof Button) {
if (isRunning) {
isRunning = false;
startStop.setLabel("Start");
stop();
}
else {
isRunning = true;
startStop.setLabel("Stop");
start();
}
return true;
}
if (e.target instanceof TextField) {
try {
this.newSize = Integer.parseInt(dotSizeField.getText());
}
catch (NumberFormatException x) {
this.newSize = -1;
}
return true;
}
return false;
} // end of boolean action
} // end of coloredDot