GAMES LESSON Eightteen: Menu
Panels and buttons can be added to an applet to provide a basic menu. These
items can be placed into the applet in various ways. The following example
shows a really simple panel containing three buttons. Try it out.
The panel and button are declared before the init method like this:
<![CDATA[
Panel menuSpace;
Button resetB, pauseB, colorB;
]]>
They are initiated in the init method like this:
<![CDATA[
resetB = new Button("RESET");
resetB.setBackground(Color.white);
resetB.addActionListener(this);
pauseB = new Button("PAUSE");
pauseB.setBackground(Color.white);
pauseB.addActionListener(this);
colorB = new Button("BALL COLOR");
colorB.setBackground(Color.white);
colorB.addActionListener(this);
menuSpace=new Panel();
menuSpace.setBackground(Color.green);
menuSpace.add(resetB);
menuSpace.add(pauseB);
menuSpace.add(colorB);
add(menuSpace);
]]>
Notice that they are hooked up to an ActionListener. Inspect the code for
the entire applet (shown below) to see how the ActionListener is organized.
MENU.java
<![CDATA[
import java.awt.*;
import java.applet.*;
import java.util.*;
import java.awt.event.*;
public class MENU extends Applet implements Runnable, ActionListener{
Dimension d;
Image offI;
Thread tt;
int y,x,cc;
double speed, xspeed;
final static double dec=1.2;
final static double acc=.9;
final static double xdec=.001;
boolean up, not_pause, left;
int floor;
Panel menuSpace;
Button resetB, pauseB, colorB;
Color COLORS[] = { Color.green, Color.red, Color.blue,
Color.black, Color.magenta, Color.cyan, Color.white };
Color curr_color = Color.green;
public void init(){
d = getSize();
floor = d.height-20;
resetB = new Button("RESET");
resetB.setBackground(Color.white);
resetB.addActionListener(this);
pauseB = new Button("PAUSE");
pauseB.setBackground(Color.white);
pauseB.addActionListener(this);
colorB = new Button("BALL COLOR");
colorB.setBackground(Color.white);
colorB.addActionListener(this);
menuSpace=new Panel();
menuSpace.setBackground(Color.green);
menuSpace.add(resetB);
menuSpace.add(pauseB);
menuSpace.add(colorB);
add(menuSpace);
reset();
offI=createImage(d.width,d.height);
tt = new Thread(this);
tt.start();
}
public void actionPerformed(ActionEvent e) {
Object src = e.getSource();
if(src == resetB){
reset();
}
else if(src == pauseB){
not_pause=!not_pause;
}
else if(src == colorB){
cc++;
cc%=COLORS.length;
curr_color=COLORS[cc];
}
}
public void reset(){
not_pause = true;
y = 0;
x = 0;
speed=1;
xspeed=4;
}
public void run(){
while(true){
if(not_pause){
if(up){
y-=(int)speed;
speed-=dec;
}
else{
y+=(int)speed;
speed+=acc;
}
if(left){
x-=(int)xspeed;
}
else{
x+=(int)xspeed;
}
if(xspeed>0) xspeed -= xdec;
if(!up && y>floor-5) up=true;
else if(up && y<0) up=false;
else if(speed<=0) up=false;
if(!left && x>d.width) left=true;
else if(left && x<0) left=false;
repaint();
try{
Thread.sleep(30);
}catch(InterruptedException ie){ }
}
}
}
public void update(Graphics g){
paint(g);
}
public void paint(Graphics g){
Graphics offG = offI.getGraphics();
offG.setColor(Color.yellow);
offG.fillRect(0,0,d.width,d.height);
offG.setColor(curr_color);
offG.fillOval(x,y,10,10);
offG.drawLine(0,floor,d.width,floor);
g.drawImage(offI, 0,0, this);
}
}
]]>
ASSIGNMENT: