Java遊戲中延遲下載資源及調用示例

（源碼依舊在Jar中）

源碼下載地址：[url]http://code.google.com/p/loon-simple/downloads/list[/url]

老實說，延遲下載遊戲資源及調用只是一種輔助手段，與遊戲開發本身關係並不大，實質也無非只是文件下載及文件讀取的混用。但考慮到上週有網友問及此類問題，筆者覺得與其回郵件單獨解釋，倒不如寫篇博文看起來更具體清晰，還能令大家幫助筆者斧正刊誤，故成此文，僅供參考。

一般來講，我們之所以會需要通過下載方式加載遊戲資源，無非是出於如下幾種目的：

1、精簡遊戲體積：

     假設我做了個100MB的遊戲，卻非想把它宣傳成僅有1MB的精巧程序，這時我該怎麼辦呢？

    去欺騙用戶，用大量複雜的技術名詞忽悠他們說1MB和100MB等值嗎？——用戶不是傻子，至少不都是傻子，無論你的話術多麼巧妙，也很難讓絕大部分人都相信1MB和100MB是一樣的。但大話已然出口，始終要想辦法解決。

     其實呢，在現有技術體系下，要搞定他們好簡單的，只需將遊戲初始界面混合下載器打包成1MB的文件發佈，再“騙”他們下載執行，而後——就讓他們慢慢等待系統加載剩下那99MB吧！畢竟沒人說過這個遊戲不需要額外的網絡資源同步嘛……

2、網遊資源的延遲加載需要：

     目前的網絡遊戲——特別是網頁遊戲，爲了儘可能的減少不必要的資源損耗，提高運行效率，大多數時候並不會一口氣將所有資源都加載到遊戲中，而是“大而化之，分而治之”，將遊戲資源構建成一個個小小的資源包，僅僅在需要時，才或同步、或異步的加載到遊戲中。這也正是我們在很多網遊中所見到的，當角色過屏、讀取新地圖或遭遇新怪物時，畫面會出現稍候字樣或者部分馬賽克乃至停頓的原因。

     故此，通過網絡適時地去加載需要的資源，幾乎已成爲網遊開發中必不可少的技巧之一。

3、融入特殊的加密解密機制：

   我們都知道，但凡是人所做出的程序，就沒有人所不能破解掉的。但是——卻很可能發生一個人做出來的程序，另一個人數年之內無法破解的現象。而當數年之後，另一個人破解出來時，這段程序卻早已過氣，白送都沒人要了。

   因此，當你極端的不想自己遊戲被反向工程——尤其是想保護Java這種極好反編譯的代碼時，通過網絡下載的另一種意義便顯現出來了。你可以將下載的jar 或class乃至其它種種保存到一個不同於執行目錄的“隱祕”場所，並且無論密鑰也好，特殊結構也罷，總之變着方的將資源加密混淆，就算混淆到連你自己都不知道這是什麼東西也無所謂——能解釋成字節碼就好，最大限度的增加反向難度。而當你執行完畢，再一刪了事——下次還可以再下嘛。這樣做的話，雖然不能徹底杜絕代碼被他人盜用，但，至少也可讓反向我代碼那哥們累掉層皮（^^）。

4、本地程序及資源合法性驗證：

    在大多數網絡遊戲中，爲了保證用戶不做出一些諸如使用外掛的“犯規”行爲，是會對系統環境乃至封包數據進行合法性驗證的，而一旦發現“非法”的東西存在，則會令“違法”玩家吊線或者乾脆封號以示懲罰。

    但這些驗證，主要都只針對程序“外部”，即當“犯規”對象“不是我的遊戲時”才能發揮功效，但萬一“犯規”者“來自遊戲本身時”或者“驗證程序認爲來自遊戲本身時”，則變得無能爲力，這也是爲什麼大多數網遊都“內掛”氾濫的緣故。

    幸運的是，Java程序由於其“天資所限”，是很難在虛擬機外部被攻破利用的，如果用Java製作網遊，原則上大可不必擔心“內掛”問題——但，這也有個大前提，那就是在“內掛”運行於虛擬機之外時才行的通。

    而如果“內掛”運行在虛擬機之內呢？如果我的“內掛”是一小段插入原始遊戲中的代碼呢？要知道，動態加載class，動態修改字節碼，早就不算什麼事情了。

    這時，就需要校驗Java程序的合法性。

    本來要驗證這種事情是比較耗費時間的，但如果我們善於利用每次下載資源（比較大的，比如過圖或者遊戲更新），如果不單單“下載”，更同步“上行”，利用空檔同服務器校對本地Java程序的合法性及完整性，便能很大程度上避免這種無意義的校驗時間浪費。這時有缺少的文件便添加，有多餘的——也就是出現不該存在的Jar或class乃至原始字節碼修改，便藉機強行“咔”掉它，免得它“爲禍人間”。

5、系統升級：

     通常來說，大多數的程序是不可能一個版本用到底的，遊戲也不例外，無論是功能的增加或者Bug修正都離不開系統的更新。爲了避免每次升級都令用戶面臨重裝的苦惱，通過網絡下載更新資源並自動更新系統也就變得非常必要。

如何實現：

下面我給出一個簡單的資源延遲下載Java實現示例，分別加載我以前博文中出現的兩個示例程序，並運行其中之一。(PS:由於本例加載的資源爲Jar，所以進行了動態類加載操作，當我們下載其它資源類型，比如僅包含圖片的zip壓縮文件時，下載的步驟還是一致，只不過要將操作換成讀取壓縮文件及加載壓縮文件資源而已。)

DownloadTool.java(這是一個簡單的下載工具類，內置有下載狀態顯示及下載條繪製)

package org.loon.game.simple.download;

import java.awt.Color;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;
import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

/**
* Copyright 2008 - 2009
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* [url]http://www.apache.org/licenses/LICENSE-2.0[/url]
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*
* @project loonframework
* @author chenpeng
* @email：[email][email protected][/email]
* @version 0.1
*/
public class DownloadTool implements Runnable {

  final static private Font font = new Font("黑體", 0, 14);

  private Rectangle rectangle;

  final static private Image barImage = GraphicsUtils
      .loadImage("image/bar.png");

  final static private int MAX_BUFFER_SIZE = 2048;

  final static private int DOWNLOADING = 0;

  final static private int PAUSED = 1;

  final static private int COMPLETE = 2;

  final static private int CANCELLED = 3;

  final static private int ERROR = 4;

  private Image backgroundBarImage;

  private Image progressBarImage;

  private Image dialogBarImage;

  private URL url;

  private int size;

  private int downloaded;

  private int contentLength;

  private int status;

  private DownloadListen listen;

  private String downloadName;

  /**
    * 創建進度條提示框
    *
    * @param object
    * @param w
    * @param h
    * @param filtrate
    * @return
    */
  private static Image createDialog(Image object, int w, int h,
      boolean filtrate) {
    Image barImage = null;
    if (filtrate) {
      barImage = GraphicsUtils.drawClipImage(object, 249, 30, 1, 57);
      barImage = GraphicsUtils.transBlackColor(barImage);
    } else {
      barImage = GraphicsUtils.drawClipImage(object, 249, 27, 0, 0);
    }
    Image imageLeft = GraphicsUtils.drawClipImage(barImage, 8, 27, 0, 0);
    Image imageRight = GraphicsUtils.drawClipImage(barImage, 8, 27, 241, 0);
    Image ImageCenter = GraphicsUtils
        .drawClipImage(barImage, 233, 27, 8, 0);
    ImageCenter = GraphicsUtils.getResize(ImageCenter, w, h);
    Graphics cg = ImageCenter.getGraphics();
    cg.drawImage(imageLeft, 0, 0, null);
    cg.drawImage(imageRight, w - 8, 0, null);
    cg.dispose();
    return ImageCenter;
  }

  /**
    * 構造函數，加載指定url
    *
    * @param url
    */
  public DownloadTool(String url) {
    this.size = -1;
    this.downloaded = 0;
    this.status = DOWNLOADING;
    try {
      this.url = new URL(url);
    } catch (MalformedURLException e) {
      throw new RuntimeException(e);
    }
  }

  public DownloadTool(URL url) {
    this.url = url;
    this.size = -1;
    this.downloaded = 0;
    this.status = DOWNLOADING;
  }

  /**
    * 設定進度條所在方位
    *
    * @param x
    * @param y
    * @param w
    * @param h
    */
  public void setRectangle(int x, int y, int w, int h) {
    setRectangle(new Rectangle(x, y, w, h));
  }

  /**
    * 設定進度條所在方位
    *
    * @param rectangle
    */
  public void setRectangle(Rectangle rectangle) {
    this.backgroundBarImage = GraphicsUtils.drawClipImage(barImage, 249,
        27, 0, 0);
    this.backgroundBarImage = createDialog(backgroundBarImage,
        rectangle.width - 21, rectangle.height - 2, false);
    // this.progressBarImage = GraphicsUtils.drawClipImage(barImage, 27, 27,
    // 28, 28);
    // this.progressBarImage = GraphicsUtils.drawClipImage(barImage, 27, 27,
    // 56, 28);
    this.progressBarImage = GraphicsUtils.drawClipImage(barImage, 27, 27,
        0, 28);
    this.dialogBarImage = createDialog(barImage, rectangle.width,
        rectangle.height, true);
    this.rectangle = rectangle;
  }

  /**
    * 返回當前url地址
    *
    * @return
    */
  public String getUrl() {
    return url.toString();
  }

  /**
    * 返回當前下載文件總長度
    *
    * @return
    */
  public int getSize() {
    return size;
  }

  /**
    * 返回當前下載已完成長度
    *
    * @return
    */
  public int getLevel() {
    return downloaded;
  }

  /**
    * 返回當前進度
    *
    * @return
    */
  public int getProgress() {
    return (int) ((double) downloaded / (double) size * 100);
  }

  public int getStatus() {
    return status;
  }

  public void pause() {
    status = PAUSED;
  }

  public void resume() {
    status = DOWNLOADING;
    download(listen);
  }

  public void cancel() {
    status = CANCELLED;
  }

  private void error() {
    status = ERROR;
  }

  public int getContentLength() {
    return contentLength;
  }

  public void download(DownloadListen listen) {
    this.listen = listen;
    Thread thread = new Thread(this);
    thread.start();
  }

  private String getFileName(URL url) {
    String fileName = url.getFile();
    return fileName.substring(fileName.lastIndexOf('/') + 1);
  }

  public String getFileName() {
    return getFileName(url);
  }

  public boolean isExists() {
    return new File(getFileName()).exists();
  }

  public String getDownloadName() {
    return downloadName;
  }

  public void setDownloadName(String downloadName) {
    this.downloadName = downloadName;
  }

  /**
    * 進行文件下載並顯示進度
    */
  public void run() {
    if (!isExists()) {
      RandomAccessFile file = null;
      InputStream stream = null;
      try {
        HttpURLConnection connection = (HttpURLConnection) url
            .openConnection();
        connection.setRequestProperty("Range", "bytes=" + downloaded
            + "-");
        connection.connect();
        if (connection.getResponseCode() / 100 != 2) {
          error();
        }
        contentLength = connection.getContentLength();
        if (contentLength < 1) {
          error();
        }
        if (size == -1) {
          size = contentLength;
        }
        file = new RandomAccessFile(getFileName(url), "rw");
        file.seek(downloaded);
        stream = connection.getInputStream();
        while (status == DOWNLOADING) {
          byte buffer[];
          if (size - downloaded > MAX_BUFFER_SIZE) {
            buffer = new byte[MAX_BUFFER_SIZE];
          } else {
            buffer = new byte[size - downloaded];
          }
          int read = stream.read(buffer);
          if (read == -1) {
            break;
          }
          file.write(buffer, 0, read);
          downloaded += read;
          listen.updateScreen();
        }
        if (status == DOWNLOADING) {
          status = COMPLETE;
          listen.call();
        }
      } catch (Exception e) {
        error();
      } finally {
        if (file != null) {
          try {
            file.close();
            file = null;
          } catch (Exception e) {
          }
        }
        if (stream != null) {
          try {
            stream.close();
            stream = null;
          } catch (Exception e) {
          }
        }
      }
    } else {
      status = COMPLETE;
      listen.call();
    }
  }

  /**
    * 繪製下載進度
    *
    * @param g
    */
  public synchronized void draw(Graphics g) {
    int progress = getProgress();
    double ratio = (double) ((double) getLevel() / (double) getSize());
    int offset = (int) (rectangle.width * ratio);
    g.drawImage(backgroundBarImage, rectangle.x + 19, rectangle.y, null);
    g.drawImage(progressBarImage, rectangle.x + 1, rectangle.y,
        offset + 20, rectangle.height - 2, null);
    g.drawImage(dialogBarImage, rectangle.x, rectangle.y, null);
    g.setFont(font);
    String mes = (getDownloadName() + ",已完成進度 : " + progress + " %")
        .intern();
    FontMetrics fm = g.getFontMetrics();
    int w = fm.stringWidth(mes);
    int h = fm.getHeight() + 2;
    g.setColor(Color.white);
    GraphicsUtils.setRenderingHints(g);
    g.drawString(mes, (rectangle.x + rectangle.width) / 2 - w / 2,
        rectangle.y + h);
  }

}

DownloadCanvas.java(下載條及背景顯示用畫布)

package org.loon.game.simple.download;

import java.awt.Canvas;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.Window;
import java.awt.image.BufferStrategy;
import java.util.ArrayList;
import java.util.List;

/**
* Copyright 2008 - 2009
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* [url]http://www.apache.org/licenses/LICENSE-2.0[/url]
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*
* @project loonframework
* @author chenpeng
* @email：[email][email protected][/email]
* @version 0.1
*/
public class DownloadCanvas extends Canvas implements DownloadListen {
  /**
    *
    */
  private static final long serialVersionUID = 1L;

  private DownloadTool progress;

  private Graphics canvasGraphics = null;

  private BufferStrategy bufferStrategy;

  private Image backgroundImage = GraphicsUtils
      .loadImage("image/background.jpg");

  private boolean initFlag;

  private Window window;

  final static List downloadList = new ArrayList(2);

  /**
    * 預定下載的文件
    */
  static {
    DownloadTool download1 = new DownloadTool(
        "http://loon-simple.googlecode.com/files/Java25DSimple.jar");
    download1.setDownloadName("下載Java2.5D八法行走示例中");
    DownloadTool download2 = new DownloadTool(
        "http://greenvm.googlecode.com/files/LocalOS_src.rar");
    download2.setDownloadName("下載Java外掛入門示例中");
    downloadList.add(download1);
    downloadList.add(download2);
  }

  public void call() {
    if (downloadList.size() == 0) {
      window.setVisible(false);
      window.dispose();
      JarLoaderUtils.callJarMain("Java25DSimple.jar");
    } else {
      progress = (DownloadTool) downloadList.remove(0);
      progress.setRectangle(rectangle);
      progress.download(this);
    }
  }

  final Rectangle rectangle;

  public void createBufferGraphics() {
    createBufferStrategy(2);
    bufferStrategy = getBufferStrategy();
  }

  public DownloadCanvas(Window window, int width, int height) {
    int pw = 600;
    int ph = 27;
    this.rectangle = new Rectangle(width / 2 - pw / 2, height / 2 - ph / 2,
        pw, ph);
    this.window = window;
    this.call();
  }

  public synchronized void updateScreen() {
    canvasGraphics = bufferStrategy.getDrawGraphics();
    if (!initFlag) {
      canvasGraphics.drawImage(backgroundImage, 0, 0, null);
      initFlag = true;
    } else {
      progress.draw(canvasGraphics);
    }
    bufferStrategy.show();
    canvasGraphics.dispose();
    Toolkit.getDefaultToolkit().sync();
    Thread.yield();
  }

}

Main.java(主類，用以啓動此下載示例)

package org.loon.game.simple.download;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

/**
* Copyright 2008 - 2009
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* [url]http://www.apache.org/licenses/LICENSE-2.0[/url]
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*
* @project loonframework
* @author chenpeng
* @email：[email][email protected][/email]
* @version 0.1
*/

public class Main extends Frame    {
  /**
    *
    */
  private static final long serialVersionUID = 1L;

  public Main(String titleName, int width, int height) {
    this.setTitle(titleName);
    this.setBackground(Color.black);
    this.setPreferredSize(new Dimension(width + 5, height + 25));
    this.requestFocus();
    this.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
         DownloadCanvas progress = new DownloadCanvas(this,width,height);
         this.add(progress);
    this.pack();
    progress.createBufferGraphics();
    this.setResizable(false);
    this.setLocationRelativeTo(null);
    this.setIgnoreRepaint(true);
    this.setVisible(true);
  }



  public static void main(String[] args) {
    java.awt.EventQueue.invokeLater(new Runnable() {
      public void run() {
        new Main("下載遊戲數據", 640, 480);
      }
    });
  }

}

程序執行效果如下圖所示：

下載完畢後後將自動加載並執行下載的Java2.5D行走示例，畫面如下圖：

（源碼依舊在Jar中）

源碼下載地址：[url]http://code.google.com/p/loon-simple/downloads/list[/url]

Java遊戲中延遲下載資源及調用示例

物理機開關機

前端使用 Konva 實現可視化設計器（15）- 自定義連接點、連接優化

Java版×××圖像過濾入門示例及源碼-0.1.0 （模擬GreenDam過濾機制）

Java版AVG遊戲開發入門[1] —— CG的繪製

上半年私人計劃簡略及Java桌面遊戲開發入門示例並源碼集合

微點。贏乎？輸耶？

Java外掛開發入門示例

Mac下配置sublime實現LaTeX

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

linux以太網驅動總結