JAVA图形操作中FPS的计算（附带随机生成乱数球体用例）

FPS：即帧 /秒(frames per
second)的缩写，也称为帧速率。是指1秒钟时间里刷新的图片的帧数，也可以理解为图形处理器每秒钟能够刷新几次。如果具体到手机上就是指每秒钟能够
播放（或者录制）多少格画面。同时越高的帧速率可以得到更流畅、更逼真的动画。每秒钟帧数(fps)越多，所显示的动作就会越流畅。

在绝大多数图形程序中（以游戏类为典型），执行效率都以FPS作为评估标准。

由于目前JAVA方面缺少相关用例，故完成功能如下图(在本机测试中，最大fps设定为500，实际达到FPS效率在IDE中280左右，单独运行380左右，受系统配置等因素影响)：

代码如下：

（请变更文件后缀为jar）



FPS部分相关源码：

package org.test;

import java.text.DecimalFormat;

/**
* <p>Title: LoonFramework</p>
* <p>Description:</p>
* <p>Copyright: Copyright (c) 2007</p>
* <p>Company: LoonFramework</p>
* @author chenpeng
* @email：[email]ceponline@yahoo.com.cn[/email]
* @version 0.1
*/
public class FPSListen {
//设定动画的FPS桢数，此数值越高,动画速度越快。
public static final int FPS = 500;

// 换算为运行周期
public static final long PERIOD = (long) (1.0 / FPS * 1000000000); // 单位: ns(纳秒)

// FPS最大间隔时间，换算为1s = 10^9ns
public static long FPS_MAX_INTERVAL = 1000000000L; // 单位: ns

// 实际的FPS数值
private double nowFPS = 0.0;

// FPS累计用间距时间
private long interval = 0L; // in ns
private long time;

//运行桢累计
private long frameCount = 0;

//格式化小数位数
private DecimalFormat df = new DecimalFormat("0.0");

//开启opengl
public void opengl(){
System.setProperty("sun.java2d.opengl", "True");
System.setProperty("sun.java2d.translaccel", "True");
}

/** *//**
* 制造FPS数据
*
*/
public void makeFPS() {
frameCount++;
interval += PERIOD;

//当实际间隔符合时间时。
if (interval >= FPS_MAX_INTERVAL) {
//nanoTime()返回最准确的可用系统计时器的当前值，以毫微秒为单位
long timeNow = System.nanoTime();
// 获得到目前为止的时间距离
long realTime = timeNow - time; // 单位: ns

//换算为实际的fps数值
nowFPS = ((double) frameCount / realTime) * FPS_MAX_INTERVAL;
//变更数值
frameCount = 0L;
interval = 0L;
time = timeNow;
}
}
public long getFrameCount() {
return frameCount;
}
public void setFrameCount(long frameCount) {
this.frameCount = frameCount;
}
public long getInterval() {
return interval;
}
public void setInterval(long interval) {
this.interval = interval;
}
public double getNowFPS() {
return nowFPS;
}
public void setNowFPS(double nowFPS) {
this.nowFPS = nowFPS;
}
public long getTime() {
return time;
}
public void setTime(long time) {
this.time = time;
}
public String getFPS(){
return df.format(nowFPS);
}

}

球体类相关代码：
package org.test;

import java.awt.Color;
import java.awt.Graphics;

/** *//**
* <p>Title: LoonFramework</p>
* <p>Description:</p>
* <p>Copyright: Copyright (c) 2007</p>
* <p>Company: LoonFramework</p>
* @author chenpeng
* @email：[email]ceponline@yahoo.com.cn[/email]
* @version 0.1
*/
public class Ball {
private static final int SIZE = 10;
private int x, y;
protected int vx, vy;

public Ball(int x, int y, int vx, int vy) {
this.x = x;
this.y = y;
this.vx = vx;
this.vy = vy;
}

public void move() {
x += vx;
y += vy;
if (x < 0 || x > BallPanel.WIDTH - SIZE) {
vx = -vx;
}
if (y < 0 || y > BallPanel.HEIGHT - SIZE) {
vy = -vy;
}
}

public void draw(Graphics g) {
g.setColor(Color.RED);
g.fillOval(x, y, SIZE, SIZE);
}

}

FPS及球体处理用代码如下：
package org.test;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Panel;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.util.Random;

/** *//**
* <p>
* Title: LoonFramework
* </p>
* <p>
* Description:以JAVA获取FPS用演示程序及随机生成乱数球体。(更优化代码内置于loonframework-game框架中)
* </p>
* <p>
* Copyright: Copyright (c) 2007
* </p>
* <p>
* Company: LoonFramework
* </p>
*
* @author chenpeng
* @email：[email]ceponline@yahoo.com.cn[/email]
* @version 0.1
*/
public class BallPanel extends Panel implements Runnable {

/** *//**
*
*/
private static final long serialVersionUID = 1L;

public static final int WIDTH = 360;

public static final int HEIGHT = 360;

// 设定最大球体数量
private static final int NUM_BALLS = 50;

// 定义球体数组
private Ball[] ball;

// 运行状态
private volatile boolean running = false;

private Thread gameLoop;

// 缓存用图形
private Graphics bg;

private Image screen = null;

// 生成随机数
private Random rand;

// fps监听
private FPSListen fps = null;

public BallPanel() {
setPreferredSize(new Dimension(WIDTH, HEIGHT));
screen = new BufferedImage(WIDTH, HEIGHT, 1);
bg = screen.getGraphics();
fps = new FPSListen();
//fps.opengl();
// 以当前毫秒生成随机数
rand = new Random(System.currentTimeMillis());
ball = new Ball[NUM_BALLS];
// 初始化球体参数
for (int i = 0; i < NUM_BALLS; i++) {
int x = rand.nextInt(WIDTH);
int y = rand.nextInt(HEIGHT);
int vx = rand.nextInt(10);
int vy = rand.nextInt(10);
ball[i] = new Ball(x, y, vx, vy);
}
}

// 加入Notify
public void addNotify() {
super.addNotify();
// 判断循环条件是否成立
if (gameLoop == null || !running) {
gameLoop = new Thread(this);
gameLoop.start();
}
}

/** *//**
* 进行线程运作。
*/
public void run() {
long beforeTime, afterTime, timeDiff, sleepTime;
long overSleepTime = 0L;
int noDelays = 0;
// 获得精确纳秒时间
beforeTime = System.nanoTime();
fps.setTime(beforeTime);
running = true;
while (running) {
gameUpdate();
repaint();
afterTime = System.nanoTime();
timeDiff = afterTime - beforeTime;
// 换算间隔时间
sleepTime = (FPSListen.PERIOD - timeDiff) - overSleepTime;
if (sleepTime > 0) {
// 制造延迟
try {
Thread.sleep(sleepTime / 1000000L); // nano->ms
} catch (InterruptedException e) {
}
// 获得延迟时间
overSleepTime = (System.nanoTime() - afterTime) - sleepTime;
} else {
// 重新计算
overSleepTime = 0L;
// 判断noDelays值
if (++noDelays >= 16) {
Thread.yield(); // 令线程让步
noDelays = 0;
}
}

// 重新获得beforeTime
beforeTime = System.nanoTime();

// 制造FPS结果
fps.makeFPS();
}

}

/** *//**
* 变更球体轨迹
*
*/
private void gameUpdate() {
for (int i = 0; i < NUM_BALLS; i++) {
ball[i].move();
}
}

/** *//**
* 变更图形
*/
public void update(Graphics g) {
paint(g);
}

/** *//**
* 显示图形
*/
public void paint(Graphics g) {

// 设定背景为白色，并清空图形
bg.setColor(Color.WHITE);
bg.fillRect(0, 0, WIDTH, HEIGHT);

// FPS数值显示
bg.setColor(Color.BLUE);
bg.drawString("FPS: " + fps.getFPS(), 4, 16);

// 分别绘制相应球体
for (int i = 0; i < NUM_BALLS; i++) {
ball[i].draw(bg);
}
g.drawImage(screen, 0, 0, this);
g.dispose();
}

public static void main(String[] args) {

Frame frm = new Frame();
frm.setTitle("Java FPS速度测试(由Loonframework框架提供)");
frm.setSize(WIDTH, HEIGHT+20);
frm.setResizable(false);
frm.add(new BallPanel());
frm.setVisible(true);
frm.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
}

}