Android实现粒子爆炸效果的方法

package net.obviam.particles.model;import android.graphics.Canvas;import android.graphics.Rect;import android.util.Log;public class Explosion {  private static final String TAG = Explosion.class.getSimpleName();  public static final int STATE_ALIVE   = 0;  // at least 1 particle is alive  public static final int STATE_DEAD   = 1;  // all particles are dead  private Particle[] particles;  // particles in the explosion  private int x, y;  // the explosion's origin  private float gravity;  // the gravity of the explosion (+ upward, - down)  private float wind;  // speed of wind on horizontal  private int size; // number of particles  private int state; // whether it's still active or not  public Explosion(int particleNr, int x, int y) {    Log.d(TAG, "Explosion created at " + x + "," + y);    this.state = STATE_ALIVE;    this.particles = new Particle[particleNr];    for (int i = 0; i < this.particles.length; i++) {      Particle p = new Particle(x, y);      this.particles[i] = p;    }    this.size = particleNr;  }  public Particle[] getParticles() {    return particles;  }  public void setParticles(Particle[] particles) {    this.particles = particles;  }  public int getX() {    return x;  }  public void setX(int x) {    this.x = x;  }  public int getY() {    return y;  }  public void setY(int y) {    this.y = y;  }  public float getGravity() {    return gravity;  }  public void setGravity(float gravity) {    this.gravity = gravity;  }  public float getWind() {    return wind;  }  public void setWind(float wind) {    this.wind = wind;  }  public int getSize() {    return size;  }  public void setSize(int size) {    this.size = size;  }  public int getState() {    return state;  }  public void setState(int state) {    this.state = state;  }  // helper methods -------------------------  public boolean isAlive() {    return this.state == STATE_ALIVE;  }  public boolean isDead() {    return this.state == STATE_DEAD;  }  public void update() {    if (this.state != STATE_DEAD) {      boolean isDead = true;      for (int i = 0; i < this.particles.length; i++) {        if (this.particles[i].isAlive()) {          this.particles[i].update();          isDead = false;        }      }      if (isDead)        this.state = STATE_DEAD;     }  }  public void update(Rect container) {    if (this.state != STATE_DEAD) {      boolean isDead = true;      for (int i = 0; i < this.particles.length; i++) {        if (this.particles[i].isAlive()) {          this.particles[i].update(container);//         this.particles[i].update();          isDead = false;        }      }      if (isDead)        this.state = STATE_DEAD;     }  }  public void draw(Canvas canvas) {    for(int i = 0; i < this.particles.length; i++) {      if (this.particles[i].isAlive()) {        this.particles[i].draw(canvas);      }    }  }}

package net.obviam.particles.model;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Rect;public class Particle {  public static final int STATE_ALIVE = 0;  // particle is alive  public static final int STATE_DEAD = 1;   // particle is dead  public static final int DEFAULT_LIFETIME  = 200; // play with this  public static final int MAX_DIMENSION    = 5;  // the maximum width or height  public static final int MAX_SPEED      = 10;  // maximum speed (per update)  private int state;     // particle is alive or dead  private float widht;    // width of the particle  private float height;    // height of the particle  private float x, y;     // horizontal and vertical position  private double xv, yv;   // vertical and horizontal velocity  private int age;      // current age of the particle  private int lifetime;    // particle dies when it reaches this value  private int color;     // the color of the particle  private Paint paint;    // internal use to avoid instantiation  public int getState() {    return state;  }  public void setState(int state) {    this.state = state;  }  public float getWidht() {    return widht;  }  public void setWidht(float widht) {    this.widht = widht;  }  public float getHeight() {    return height;  }  public void setHeight(float height) {    this.height = height;  }  public float getX() {    return x;  }  public void setX(float x) {    this.x = x;  }  public float getY() {    return y;  }  public void setY(float y) {    this.y = y;  }  public double getXv() {    return xv;  }  public void setXv(double xv) {    this.xv = xv;  }  public double getYv() {    return yv;  }  public void setYv(double yv) {    this.yv = yv;  }  public int getAge() {    return age;  }  public void setAge(int age) {    this.age = age;  }  public int getLifetime() {    return lifetime;  }  public void setLifetime(int lifetime) {    this.lifetime = lifetime;  }  public int getColor() {    return color;  }  public void setColor(int color) {    this.color = color;  }  // helper methods -------------------------  public boolean isAlive() {    return this.state == STATE_ALIVE;  }  public boolean isDead() {    return this.state == STATE_DEAD;  }  public Particle(int x, int y) {    this.x = x;    this.y = y;    this.state = Particle.STATE_ALIVE;    this.widht = rndInt(1, MAX_DIMENSION);    this.height = this.widht;//   this.height = rnd(1, MAX_DIMENSION);    this.lifetime = DEFAULT_LIFETIME;    this.age = 0;    this.xv = (rndDbl(0, MAX_SPEED * 2) - MAX_SPEED);    this.yv = (rndDbl(0, MAX_SPEED * 2) - MAX_SPEED);    // smoothing out the diagonal speed    if (xv * xv + yv * yv > MAX_SPEED * MAX_SPEED) {      xv *= 0.7;      yv *= 0.7;    }    this.color = Color.argb(255, rndInt(0, 255), rndInt(0, 255), rndInt(0, 255));    this.paint = new Paint(this.color);  }  /**   * Resets the particle   * @param x   * @param y   */  public void reset(float x, float y) {    this.state = Particle.STATE_ALIVE;    this.x = x;    this.y = y;    this.age = 0;  }  // Return an integer that ranges from min inclusive to max inclusive.  static int rndInt(int min, int max) {    return (int) (min + Math.random() * (max - min + 1));  }  static double rndDbl(double min, double max) {    return min + (max - min) * Math.random();  }  public void update() {    if (this.state != STATE_DEAD) {      this.x += this.xv;      this.y += this.yv;      // extract alpha      int a = this.color >>> 24;      a -= 2;               // fade by 5      if (a <= 0) {            // if reached transparency kill the particle        this.state = STATE_DEAD;      } else {        this.color = (this.color & 0x00ffffff) + (a << 24);    // set the new alpha        this.paint.setAlpha(a);        this.age++;           // increase the age of the particle//       this.widht *= 1.05;//       this.height *= 1.05;      }      if (this.age >= this.lifetime) { // reached the end if its life        this.state = STATE_DEAD;      }      // http://lab.polygonal.de/2007/05/10/bitwise-gems-fast-integer-math/      //32bit//     var color:uint = 0xff336699;//     var a:uint = color >>> 24;//     var r:uint = color >>> 16 & 0xFF;//     var g:uint = color >>> 8 & 0xFF;//     var b:uint = color & 0xFF;           }  }  public void update(Rect container) {    // update with collision    if (this.isAlive()) {      if (this.x <= container.left || this.x >= container.right - this.widht) {        this.xv *= -1;      }      // Bottom is 480 and top is 0 !!!      if (this.y <= container.top || this.y >= container.bottom - this.height) {        this.yv *= -1;      }    }    update();  }  public void draw(Canvas canvas) {//   paint.setARGB(255, 128, 255, 50);    paint.setColor(this.color);    canvas.drawRect(this.x, this.y, this.x + this.widht, this.y + this.height, paint);//   canvas.drawCircle(x, y, widht, paint);  }}