Java 美丽的烟花

## 技术要点

* 类Image的使用。

* 类Graphics的使用。

* 双缓冲技术处理闪烁。

## 效果展示


## 代码实现

```java

package net.xsoftlab.baike;

import java.applet.Applet;

import java.awt.Color;

import java.awt.Graphics;

import java.util.Random;

public class MissileDemo extends Applet implements Runnable {

private static final long serialVersionUID = 6219904185869794496L;

public int speed, variability, Max_Number, Max_Energy, Max_Patch, Max_Length, G;

public String sound;

// 获取当前容器边界的宽和高

private int width, height;

// 设置线程

private Thread thread = null;

// 创建BeaClassDemo类数组bcd

private BeaClassDemo bcd[];

@Override

public void init() {

int i;

// 设置当前容器的宽和高

this.setSize(700, 400);

width = getSize().width - 1;

height = getSize().height - 1;

// 烟花绽放的速度

speed = 30;

variability = 10;

// 可发出烟花的最大数目

Max_Number = 100;

Max_Energy = width + 50;

// 最大的斑点数

Max_Patch = 80;

// 斑点的最大距离

Max_Length = 200;

// 向地面弯曲的力度

G = 50;

// 初始化BeaClassDemo数组

bcd = new BeaClassDemo[Max_Number];

for (i = 0; i < Max_Number; i++)

bcd[i] = new BeaClassDemo(width, height, G);

}

@Override

public void start() {

if (thread == null) {

thread = new Thread(this);

thread.start();

}

}

@Override

@SuppressWarnings("deprecation")

public void stop() {

if (thread != null) {

thread.stop();

thread = null;

}

}

@Override

@SuppressWarnings("static-access")

public void run() {

int i;

int E = (int) (Math.random() * Max_Energy * 3 / 4) + Max_Energy / 4 + 1;

int P = (int) (Math.random() * Max_Patch * 3 / 4)// 烟花的斑点数

+ Max_Patch / 4 + 1;

int L = (int) (Math.random() * Max_Length * 3 / 4)// 烟花可发射出的距离

+ Max_Length / 4 + 1;

long S = (long) (Math.random() * 10000);// 产生的随机数

boolean sleep;// 体眠的标志

Graphics g = getGraphics();

while (true) {

try {

thread.sleep(1000 / speed);

} catch (InterruptedException x) {}

sleep = true;

for (i = 0; i < Max_Number; i++)

sleep = sleep && bcd[i].sleep;

if (sleep && Math.random() * 100 < variability) {

E = (int) (Math.random() * Max_Energy * 3 / 4) + Max_Energy / 4 + 1;

P = (int) (Math.random() * Max_Patch * 3 / 4) + Max_Patch / 4 + 1;

L = (int) (Math.random() * Max_Length * 3 / 4) + Max_Length / 4 + 1;

S = (long) (Math.random() * 10000);

}

for (i = 0; i < Max_Number; i++) {

if (bcd[i].sleep && Math.random() * Max_Number * L < 1) {

bcd[i].init(E, P, L, S);

bcd[i].start();

}

bcd[i].show(g);

}

}

}

@Override

public void paint(Graphics g) {// 绘制组件

g.setColor(Color.black);// 设置背景颜色为黑

g.fillRect(0, 0, width + 1, height + 1);// 根据参数画矩形

}

}

class BeaClassDemo {

private Random random;

public boolean sleep = true;

private int energy, patch, length, width, height, G, Xx, Xy, Ex[], Ey[], x, y, Red, Blue, Green, t;

public BeaClassDemo(int a, int b, int g) {

width = a;

height = b;

G = g;

}

public void init(int e, int p, int l, long seed) {

int i;

// 赋值运算

energy = e;

patch = p;

length = l;

// 创建一个带种子的随机数生成器

random = new Random(seed);

Ex = new int[patch];// 初始化int数组Ex，其长度为patch

Ey = new int[patch];// 初始化int数组Ey，其长度为patch

// 随机生成不透明的 sRGB 颜色值

Red = (int) (random.nextDouble() * 128) + 128;

Blue = (int) (random.nextDouble() * 128) + 128;

Green = (int) (random.nextDouble() * 128) + 128;

Xx = (int) (Math.random() * width / 2) + width / 4;

Xy = (int) (Math.random() * height / 2) + height / 4;

for (i = 0; i < patch; i++) {

Ex[i] = (int) (Math.random() * energy) - energy / 2;

Ey[i] = (int) (Math.random() * energy * 7 / 8) - energy / 8;

}

}

public void start() {

t = 0;

sleep = false;

}

// 展示烟花

public void show(Graphics g) {

// 如果休眠，就直接返回

if (sleep)

return;

if (t < length) {

int i, c;

double s;

Color color;

c = (int) (random.nextDouble() * 64) - 32 + Red;

if (c >= 0 && c < 256)

Red = c;

c = (int) (random.nextDouble() * 64) - 32 + Blue;

if (c >= 0 && c < 256)

Blue = c;

c = (int) (random.nextDouble() * 64) - 32 + Green;

if (c >= 0 && c < 256)

Green = c;

color = new Color(Red, Blue, Green);

for (i = 0; i < patch; i++) {

s = (double) t / 100;

x = (int) (Ex[i] * s);

y = (int) (Ey[i] * s - G * s * s);

g.setColor(color);

g.drawLine(Xx + x, Xy - y, Xx + x, Xy - y);

if (t >= length / 2) {

int j;

for (j = 0; j < 2; j++) {

s = (double) ((t - length / 2) * 2 + j) / 100;

x = (int) (Ex[i] * s);

y = (int) (Ey[i] * s - G * s * s);

g.setColor(Color.black);

g.drawLine(Xx + x, Xy - y, Xx + x, Xy - y);

}

}

}

t++;

} else {

sleep = true;

}

}

}

```

## 程序解读

1. MissileDemo类随机生成烟花的颜色，这种随机的颜色可以通过RGB来实现颜色的分配。

2. 在运行烟花程序时，烟花绽放的颜色通过上面的方法可以控制，现在就得对烟花的速度进行一定的控制，主要是通过speed属性来控制。另外，就是对烟花的斑点数进行控制，可以参照下面的方法：(Math.random()\*Max_Patch\*3/4)

3. 最后就可以运行小程序，输出烟花，看到它绽放的效果。