Piano World:
public class Key extends Actor
{
private String image1;
private String image2;
private boolean isDown;//true: key is down...false: key is up
private String keyboard;
private String soundFile;
/**
* , Computer Science Math 2012, java.
* Relates the images and strings
*/
public Key(String k, String sound, String keyUp, String keyDown)
{
{
keyboard = k;
sound = soundFile;
image1 = keyUp;
image2 = keyDown;
setImage(image1);
}
}
/**
* , Computer Science Math 2012, java.
* Do the action for this key.
*/
public void act()
{
animate();
}
/**
* , Computer Science Math 2012, java.
* animates the keys
*/
public void animate()
{
if ( !isDown && Greenfoot.isKeyDown(keyboard))
{
play();
setImage (image2);
isDown = true;
}
if ( isDown && !Greenfoot.isKeyDown(keyboard))
{
setImage (image1);
isDown = false;
}
}
/**
* , Computer Science Math 2012, java.
* play the sound file when key is clicked or when a key and space is clicked.
*/
public void play()
{
if(!Greenfoot.isKeyDown("space") && Greenfoot.isKeyDown(keyboard))
{
Greenfoot.playSound(soundFile);
}
}
}
KEY CLASS:
public class Piano extends World
{
private String letters = {"a", "s", "d", "f", "g", "h", "j", "k", "l", ";", "'","enter"};
private String files = {"3c.wav", "3d.wav", "3e.wav", "3f.wav", "3g.wav", "3a.wav", "3b.wav", "4c.wav", "4d.wav", "4e.wav", "4f.wav", "4g.wav"};
private String lower = {"2c.wav", "2d.wav", "2e.wav", "2f.wav", "2g.wav", "2a.wav", "2b.wav", "3c.wav", "3d.wav", "3e.wav", "3f.wav", "3g.wav"};
private String bLetters = {"w", "e", "", "t", "y", "u", "", "o", "p"};
private String bFiles = {"3c#.wav", "3d#.wav", "", "3f#.wav", "3g#.wav", "3a#.wav", "", "4c#.wav", "4d#.wav"};
private String bLower = {"2c#.wav", "2d#.wav", "", "2f#.wav", "2g#.wav", "2a#.wav", "", "3c#.wav", "3d#.wav"};
/**
* , Computer Science Math 2012, java.
* Make the piano.
*/
public Piano()
{
super(800, 340, 1);
makeKeys();
showMessage();
}
/**
* , Computer Science Math 2012, java.
* Makes the white and black keys.
*/
public void makeKeys()
{
int i = 0;
while(i < 12)
{
if(letters != "")
{
Key key = new Key(letters, files, "white-key.png", "white-key-down.png");
addObject(key,54 + (i*63), 140);
i++;
}
}
int a = 0;
while(a < 9)
{
if(bLetters != "")
{
Key key = new Key(bLetters, bFiles, "black-key.png", "black-key-down.png");
addObject(key,150 + (a*63), 86);
}
a++;
}
}
/**
* , Computer Science Math 2012, java.
* Shows a message in red at the bottom of the world.
*/
public void showMessage()
{
GreenfootImage bg = getBackground();
bg.setColor(Color.GREEN);
bg.drawString("Click 'Run', then use a,s,d,f,g,h,j,k,l,;,',enter,q,w,e,t,y,u,… to make sounds.", 25, 320);
}
}
The code compiles, however, when I go to click a key, an error pops up
"java.lang.NullPointerExecption: Filename must not be null.
at Key.play(Key,java:64)
at Key.animate(Key.Java:43)
at Key.act(Key.java:32)"
Can anyone please explain what I am doing wrong? I have tried to find new outlets and nothing is working.
