GAMES LESSON ELEVEN: Keyboard Events
We've already seen how to trigger events with the keyboard. In this lesson
we discuss taking input from the keyboard. Take a look at the sample applet.
We had to modify the keyPressed method in order to take user input. Here's
the altered method:
<![CDATA[
requestFocus();
this.addKeyListener(new KeyAdapter(){
public void keyPressed(KeyEvent k) {
if(k.getKeyCode() != KeyEvent.VK_SHIFT){
if(!gameOver){
user+=k.getKeyChar();
check();
}
else{
repaint();
}
}
}
});
]]>
As you can see after user input is taken a call is made to the check method
which compares the user input to the correct input. If the user matches the
proper letter, a new letter is displayed through a call to the spawn method.
You can trace the activity of the applet by inspecting the code shown below:
KEY.java
<![CDATA[
import java.awt.*;
import java.applet.*;
import java.util.*;
import java.awt.event.*;
public class KEY extends Applet implements Runnable{
Dimension d;
Image offI;
Thread tt;
int x, y, index;
String user = "";
String letter = "";
String letters = "abcdefghijklmnopqrstuvwxyz";
boolean gameOver;
Random r;
public void init(){
d = getSize();
r=new Random();
spawn();
offI=createImage(d.width,d.height);
tt = new Thread(this);
tt.start();
requestFocus();
this.addKeyListener(new KeyAdapter(){
public void keyPressed(KeyEvent k) {
if(k.getKeyCode() != KeyEvent.VK_SHIFT){
if(!gameOver){
user+=k.getKeyChar();
check();
}
else{
repaint();
}
}
}
});
}
public void check(){
if(user.equals(letter)){
if(index<letters.length()) spawn();
else gameOver=true;
}
user="";
}
public void spawn(){
letter = letters.substring(index,index+1);
x = Math.abs(r.nextInt()%400)+20;
y = 0;
index++;
}
public void run(){
while(!gameOver){
y+=3;
if(y>d.height) y = 0;
repaint();
try{
Thread.sleep(50);
}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(Color.black);
if(!gameOver) offG.drawString(letter, x, y);
else offG.drawString("GAME OVER", 50,50);
offG.drawString("INDEX: " + index, 10, 150);
g.drawImage(offI, 0,0, this);
}
}
]]>
ASSIGNMENT: