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。