smallball.java

j2me手机上的音频开发

/*
 * @(#)SmallBall.java	1.6 04/03/11
 *
 * Copyright (c) 1999-2004 Sun Microsystems, Inc. All rights reserved.
 * PROPRIETARY/CONFIDENTIAL
 * Use is subject to license terms
 */

package example.audiodemo;

import javax.microedition.lcdui.*;
import javax.microedition.media.control.*;

/**
 * A SmallBall is a lightweight animated ball that runs in its own thread.
 * It moves within a rectangular region, bouncing off the walls.
 */
class SmallBall implements Runnable {

    // random number generator
    static java.util.Random random = new java.util.Random();

    // Global flag to temporarily pause all balls
    public static boolean paused = false;

    private final static int DEFAULT_DELAY = 8;
    private final static int MIN_DELAY = 1;
    private final static int MAX_DELAY = 128;

    // controls the speed of all balls; delay in milliseconds
    static int delay = DEFAULT_DELAY;

    static void slower() {
	delay *= 2;
	if (delay > MAX_DELAY) delay = MAX_DELAY;
    }

    static void faster() {
	delay /= 2;
	if (delay < MIN_DELAY) delay = MIN_DELAY;
    }

    /**
     * Returns the speed in percent of
     * the DEFAULT_DELAY
     */
    static int getSpeedPercent() {
	int ret = 100; // start with 100%
	int thisDelay = delay;
	while (thisDelay > DEFAULT_DELAY) {
	    thisDelay /= 2;
	    ret -= 10;
	}
	while (thisDelay < DEFAULT_DELAY) {
	    thisDelay *= 2;
	    ret += 10;
	}
	return ret;
    }



    // the matrix to transform the direction based on the
    // current direction and which wall was hit
    static int[][] matrix = {
	{  1,-1,  -1, 1,   1, 1 },
	{ -1,-1,   1, 1,  -1, 1 },
	null,
	{  1, 1,  -1,-1,   1,-1 },
	{ -1, 1,   1,-1,  -1,-1 }
    };

    // the region in which the ball moves
    int top, left, width, height;

    // the position and radius of the ball
    int posX, posY;
    int radius = 5, ballSize = radius*2;

    // the direction of the ball is controlled by these two variables
    int deltaX;
    int deltaY;

    // a handle onto the singleton Graphics object
    Graphics g;
    Canvas canvas;
    int note = ToneControl.C4;
    int clr = 0;

    // public variables to control the behaviour of the thread
    public boolean stop; // = false

    // if true, this thread will call repaint()
    public boolean doRepaint; // = false;

    /**
     * Constructor defines the region in which the ball moves as well
     * as its starting position.
     */
    SmallBall(Canvas c, int left, int top, int width, int height) {
	super();
	canvas = c;

	this.left = left + 1;
	this.top  = top + 1;
	this.width = width - (2 * radius + 2);
	this.height = height - (2 * radius + 2);

	// use positive random #s
	this.posX = (random.nextInt()>>>1) % (this.width-20) + 10;
	this.posY = (random.nextInt()>>>1) % (this.height-20) + 10;

	deltaX = random.nextInt() & 1;
	deltaY = random.nextInt() & 1;

	if (deltaX == 0) deltaX = -1;
	if (deltaY == 0) deltaY = -1;

	stop = true;
    }

    public void setNote(int note) {
	this.note = note;
    }

    /**
     * Starts the ball running.
     */
    public void run() {
	// System.out.println("starting... " + this);
	int right = left + width;
	int bottom = top + height;

	while (!stop) {

	    ballSize = radius * 2;

	    // calculate a direction of the ball as an integer in the range
	    // -2 .. 2 (excluding 0)
	    int direction = deltaX + deltaY;
	    if (direction == 0) direction = deltaX + 2*deltaY;

	    // is the current position colliding with any wall
	    int collision = 0;
	    if (posX <= left || posX >= right) collision++;
	    if (posY <= top || posY >= bottom) collision += 2;

	    // change the direction appropriately if there was a collision
	    if (collision != 0) {
		try {
		    javax.microedition.media.Manager.playTone(note, 100/*ms*/,100);
		} catch (Exception ex) {
		    System.out.println("failed to play tone");
		}

		collision = (collision - 1) * 2;

		deltaX = matrix[direction+2][collision];
		deltaY = matrix[direction+2][collision+1];
	    }

	    // calculate the new position and queue a repaint
	    posX = posX + deltaX;
	    posY = posY + deltaY;

	    if (doRepaint) {
		canvas.repaint();
	    }

	    // use the delay to control the speed of the ball
	    // if the MIDlet is paused, keep on waiting
	    do {
		try {
		    // if paused, always wait 100 millis,
		    // regardless of ball speed
		    Thread.sleep(paused?100:delay);
		} catch (InterruptedException e) {}
	    } while (paused && !stop);
	}
    }

    /**
     * Paint the ball.
     */
    void paint(Graphics g) {
	g.setColor(clr);
	g.fillArc(posX,posY,ballSize,ballSize,0,360);
    }

    public void setColor(int clr) {
	this.clr = clr;
    }

    public String toString() {
	return super.toString() + " x = " + posX + ", y = " + posY;
    }

}