FileDocCategorySizeDatePackage
ManyCanvas.javaAPI DocJ2ME MIDP 2.04750Thu Nov 07 12:02:18 GMT 2002example.manyballs

ManyCanvas

public class ManyCanvas extends javax.microedition.lcdui.Canvas

Fields Summary
Display
display
SmallBall[]
balls
int
numBalls
int
width
int
height
boolean
paused
static int
NUM_HISTORY
long[]
times
int
times_idx
String
msg
Draws the drawing frame (which also contains the ball) and the controls.
Constructors Summary
public ManyCanvas(Display d, int maxBalls)


         

	display = d;		// save the display

	// initialize the array of balls
	balls = new SmallBall[maxBalls];
	
	width = getWidth();
	height = getHeight();

	// Start with one ball
	balls[0] = new SmallBall(this, 0, 0, width, height-12-20);
	numBalls = 1;
	paused = true;
Methods Summary
voiddestroy()
Destroy

	// kill all the balls and terminate
	for (int i = 0; i < balls.length && balls[i] != null; i++) {
	    balls[i].stop = true;

	    // enable the balls to be garbage collected
	    balls[i] = null;
	}
	numBalls = 0;
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-12-20);
		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();
protected voidpaint(Graphics g)

        
        int x = g.getClipX();
        int y = g.getClipY();
        int w = g.getClipWidth();
        int h = g.getClipHeight();

	// Draw the frame 
	g.setColor(0xffffff);
	g.fillRect(x, y, w, h);

	// Draw each ball
	for (int i = 0; i < numBalls; i++) {
            if (balls[i].inside(x, y, x + w, y + h)) {
                balls[i].paint(g);
            }
	}

	g.setColor(0);
	g.drawRect(0, 0, width-1, height-1);

	long now = System.currentTimeMillis();
        String str = null;
        if (times_idx >= NUM_HISTORY) {
            long oldTime = times[times_idx % NUM_HISTORY];
            if (oldTime == now) {
                // in case of divide-by-zero
                oldTime = now - 1;
            }
            long fps = ((long)1000 * (long)NUM_HISTORY) / (now - oldTime);
            if (times_idx % 20 == 0) {
                str = numBalls + " Ball(s) " + fps + " fps";
            }
        } else {
            if (times_idx % 20 == 0) {
                str =  numBalls + " Ball(s)";
            }
        }

        if (msg != null) {
            g.setColor(0xffffff);
            g.setClip(0, height-14, width, height);
            g.fillRect(0, height-20, width-2, 18);

            g.setColor(0);
            g.drawString(msg, 5, height-14, 0);
            g.drawRect(0, 0, width-1, height-1);
            msg = null;
        }
        if (str != null) {
            /*
             * Do a complete repaint, so that the message will
             * be shown even in double-buffer mode.
             */
            repaint();
            msg = str;
        }

        times[times_idx % NUM_HISTORY] = now;
        ++ times_idx;
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 thread will terminate. TBD: is a join needed?

	if (!paused) {
	    paused = true;
	    for (int i = 0; i < balls.length && balls[i] != null; i++) {
		balls[i].stop = true;
	    }
	}
	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();
	    }
	}
	repaint();