manycanvas.java

在支持java的手机中均能运行的小球类游戏,编程环境:Windows XPsp2,JBuiledrX,Nokia SDK

package manyballs;

import javax.microedition.lcdui.*;

public class ManyCanvas extends javax.microedition.lcdui.Canvas {

    Display display;

    // a set of free roaming balls
    SmallBall[] balls;
    int numBalls;
    int width, height;
    boolean paused;
    static int NUM_HISTORY = 8;
    long times[] = new long[NUM_HISTORY];
    int times_idx;

    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;
    }

    /**
     * Draws the drawing frame (which also contains the ball) and the
     * controls.
     */
    String msg = null;
    protected void paint(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;

    }

    /**
     * Handle a pen down event.
     */
    public void keyPressed(int keyCode) {

        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();
    }

    /**
     * Destroy
     */
    void 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;
    }


    /*
     * Return whether the canvas is paused or not.
     */
    boolean isPaused() {
        return paused;
    }

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

    /*
     * Start creates a new thread for each ball and start it.
     */
    void start() {
        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();
    }


}