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BallCanvas.javaAPI DocJ2ME MIDP 2.06101Thu Nov 07 12:02:20 GMT 2002example.audiodemo

BallCanvas

public class BallCanvas extends Canvas implements CommandListener

Fields Summary
private Display
display
private Player
player
private int[]
notes
private int[]
colors
private SmallBall[]
balls
private int
numBalls
private int
width
private int
height
private boolean
paused
private Command
backCommand
private Command
pauseCommand
private Command
playCommand
private boolean
playerCreated
Constructors Summary
public BallCanvas(Display d, int maxBalls, int bg)

    
           
	display = d;
	
	// initialize the array of balls
	balls = new SmallBall[maxBalls];
	
	width = getWidth();
	height = getHeight();
	
	playerCreated = initPlayer(bg);

	// Start with one ball
	balls[0] = new SmallBall(this, 0, 0,width,height-12);
	balls[0].setColor(colors[0]);
	numBalls = 1;
	paused = true;
	
	this.addCommand(backCommand);
	this.addCommand(pauseCommand);
	setCommandListener(this);
Methods Summary
public voidcommandAction(Command c, Displayable s)

	if (c == backCommand) {
	    destroy();
	    display.setCurrent(BBall.getList());
	} else if ( c == pauseCommand) {
	    pause();
	    removeCommand(pauseCommand);
	    addCommand(playCommand);
	} else if ( c == playCommand) {
	    removeCommand(playCommand);
	    addCommand(pauseCommand);
	    start();
	}
voiddestroy()
Destroy

	// kill all the balls and terminate
	for (int i = 0; i < balls.length; i++) {
	    if (balls[i] != null) {
		balls[i].stop = true;
		balls[i] = null;
	    }
	}
	numBalls = 0;
	if ( player != null) {
	    player.close();
	    player = null;
	}
	BBall.getInstance().game = null;
booleaninitPlayer(int bg)

	try {
	    switch (bg) {
	    case 1: // wave bg
		player = Manager.createPlayer(BBall.wavbgUrl);
		break;
	    case 2: // tone seq bg
		{
		    byte d = 8; 
		    byte C4 = ToneControl.C4;
		    byte D4 = ToneControl.C4 + 2; // a whole step 
		    byte E4 = ToneControl.C4 + 4; // a major third
		    byte G4 = ToneControl.C4 + 7; // a fifth
		    byte rest = ToneControl.SILENCE; // eighth-note rest
		    
		    byte[] mySequence = new byte[] {
			ToneControl.VERSION, 1,
			    ToneControl.TEMPO, 30,
			    ToneControl.BLOCK_START, 0,
			    E4,d,D4,d,C4,d,D4,d,E4,d,E4,d,E4,d,rest,d, 
			    ToneControl.BLOCK_END,0,
			    ToneControl.PLAY_BLOCK,0,
			    D4,d,D4,d,D4,d,rest,d,E4,d,G4,d,G4,d,rest,d,//play "B" section 
			    ToneControl.PLAY_BLOCK,0, // content of "A" section 
			    D4,d,D4,d,E4,d,D4,d,C4,d,rest,d// play "C" section 
			    };
		    player = Manager.createPlayer(Manager.TONE_DEVICE_LOCATOR);
		    player.realize();
		    ToneControl c = (ToneControl)player.getControl("ToneControl");
		    c.setSequence(mySequence);
		}
		break;
	    default:
		player = null;
	    }
	    
	    if (player != null) {
		player.setLoopCount(-1);
		player.start();
	    }
	} catch (Exception ex) {
	    if ( player != null )
		player.close();
	    player = null;
	    return false;
	}
	
	return true;
booleanisPaused()

	return paused;
public voidkeyPressed(int keyCode)
Handle a pen down event.

	
	int action = getGameAction(keyCode);
	
	switch (action) {
	case LEFT:
	    // Reduce the number of threads
	    if (numBalls > 0) {
		
		// decrement the counter
		numBalls = numBalls - 1;
		
		// stop the thread and remove the reference to it
		balls[numBalls].stop = true;
		balls[numBalls] = null;
	    }
	    break;
	    
	case RIGHT:
	    // Increase the number of threads
	    if (numBalls < balls.length) {
		
		// create a new ball and start it moving
		balls[numBalls] = new SmallBall(this, 0, 0, width,height-12);
		balls[numBalls].setNote(notes[numBalls]);
		balls[numBalls].setColor(colors[numBalls]);
		
		new Thread(balls[numBalls]).start();
		
		// increment the counter
		numBalls = numBalls + 1;
	    }
	    break;
	    
	case UP:
	    // Make them move faster
	    SmallBall.faster();
	    break;
	    
	case DOWN:
	    // Make them move slower
	    SmallBall.slower();
	    break;
	}
	repaint();
booleanneedAlert()

	return (!playerCreated);
protected voidpaint(Graphics g)
Draws the drawing frame (which also contains the ball) and the controls.

	// Draw the frame 
	g.setColor(0xffffff);
	g.fillRect(0,0, width-1, height-1);
	g.setColor(0);
	g.drawRect(0+1,0+1,width-2,height-2);
	
	// Draw each ball
	for(int i = 0; i < numBalls; i++) {
	    balls[i].paint(g);
	}
voidpause()
Pause the balls by signaling each of them to stop. The ball object still exists and holds the current position of the ball. It may be restarted later. the current thread will be terminated.

	if (!paused) {
	    paused = true;
	    for (int i = 0; i < balls.length && balls[i] != null; i++) {
		balls[i].stop = true;
	    }
	    
	    try {
		if (player != null)
		    player.stop();
	    } catch (MediaException e) {
		// There's nothing much we can do here.
	    }
	}
	repaint();
voidstart()

	if (paused) {
	    paused = false;
	    // display.setCurrent(this);
	    for (int i = 0; i < balls.length && balls[i] != null; i++) {
		Thread t = new Thread(balls[i]);
		t.start();
	    }
	    
	    if ( player != null) {
		try {
		    player.start();
		} catch (Exception ex) {}
	    }

	    repaint();
	}