Android 实现网络多线程APK文件下载

(转自：http://blog.csdn.net/mad1989/article/details/38421465)

实现原理

(1)首先获得下载文件的长度，然后设置本地文件的长度。

(2)根据文件长度和线程数计算每条线程下载的数据长度和下载位置。

如：文件的长度为6M，线程数为3，那么，每条线程下载的数据长度为2M，每条线程开始下载的位置如下图所示：

例如10M大小，使用3个线程来下载，

线程下载的数据长度   (10%3 == 0 ？ 10/3:10/3+1) ,第1，2个线程下载长度是4M，第三个线程下载长度为2M
下载开始位置：线程id*每条线程下载的数据长度 = ?
下载结束位置：（线程id+1）*每条线程下载的数据长度-1=?

之前练习时的一个demo，不多说了，直接上代码吧，有关断点续传，需要使用数据库，不再加了，网上有很多成熟的项目可以直接用。

实例

MainApp：

  1 package com.amos.app;

  2 

  3 import java.io.File;

  4 import java.io.IOException;

  5 import java.net.MalformedURLException;

  6 import java.net.URL;

  7 import java.net.URLConnection;

  8 import com.amos.download.R;

  9 import android.annotation.SuppressLint;

 10 import android.app.Activity;

 11 import android.os.Bundle;

 12 import android.os.Environment;

 13 import android.os.Handler;

 14 import android.os.Message;

 15 import android.util.Log;

 16 import android.view.View;

 17 import android.view.View.OnClickListener;

 18 import android.widget.ProgressBar;

 19 import android.widget.TextView;

 20 import android.widget.Toast;

 21 

 22 /**

 23  * @author yangxiaolong

 24  * @2014-5-6

 25  */

 26 public class MainApp extends Activity implements OnClickListener {

 27 

 28     private static final String TAG = MainApp.class.getSimpleName();

 29 

 30     /** 显示下载进度TextView */

 31     private TextView mMessageView;

 32     /** 显示下载进度ProgressBar */

 33     private ProgressBar mProgressbar;

 34 

 35     @Override

 36     protected void onCreate(Bundle savedInstanceState) {

 37         super.onCreate(savedInstanceState);

 38         setContentView(R.layout.progress_activity);

 39         findViewById(R.id.download_btn).setOnClickListener(this);

 40         mMessageView = (TextView) findViewById(R.id.download_message);

 41         mProgressbar = (ProgressBar) findViewById(R.id.download_progress);

 42     }

 43 

 44     @Override

 45     public void onClick(View v) {

 46         if (v.getId() == R.id.download_btn) {

 47             doDownload();

 48         }

 49     }

 50 

 51     /**

 52      * 使用Handler更新UI界面信息

 53      */

 54     @SuppressLint("HandlerLeak")

 55     Handler mHandler = new Handler() {

 56         @Override

 57         public void handleMessage(Message msg) {

 58 

 59             mProgressbar.setProgress(msg.getData().getInt("size"));

 60 

 61             float temp = (float) mProgressbar.getProgress()

 62                     / (float) mProgressbar.getMax();

 63 

 64             int progress = (int) (temp * 100);

 65             if (progress == 100) {

 66                 Toast.makeText(MainApp.this, "下载完成！", Toast.LENGTH_LONG).show();

 67             }

 68             mMessageView.setText("下载进度:" + progress + " %");

 69 

 70         }

 71     };

 72 

 73     /**

 74      * 下载准备工作，获取SD卡路径、开启线程

 75      */

 76     private void doDownload() {

 77         // 获取SD卡路径

 78         String path = Environment.getExternalStorageDirectory()

 79                 + "/amosdownload/";

 80         File file = new File(path);

 81         // 如果SD卡目录不存在创建

 82         if (!file.exists()) {

 83             file.mkdir();

 84         }

 85         // 设置progressBar初始化

 86         mProgressbar.setProgress(0);

 87 

 88         // 简单起见，我先把URL和文件名称写死，其实这些都可以通过HttpHeader获取到

 89         String downloadUrl = "http://gdown.baidu.com/data/wisegame/91319a5a1dfae322/baidu_16785426.apk";

 90         String fileName = "baidu_16785426.apk";

 91         int threadNum = 5;

 92         String filepath = path + fileName;

 93         Log.d(TAG, "download file  path:" + filepath);

 94         downloadTask task = new downloadTask(downloadUrl, threadNum, filepath);

 95         task.start();

 96     }

 97 

 98     /**

 99      * 多线程文件下载

100      * 

101      * @author yangxiaolong

102      * @2014-8-7

103      */

104     class downloadTask extends Thread {

105         private String downloadUrl;// 下载链接地址

106         private int threadNum;// 开启的线程数

107         private String filePath;// 保存文件路径地址

108         private int blockSize;// 每一个线程的下载量

109 

110         public downloadTask(String downloadUrl, int threadNum, String fileptah) {

111             this.downloadUrl = downloadUrl;

112             this.threadNum = threadNum;

113             this.filePath = fileptah;

114         }

115 

116         @Override

117         public void run() {

118 

119             FileDownloadThread[] threads = new FileDownloadThread[threadNum];

120             try {

121                 URL url = new URL(downloadUrl);

122                 Log.d(TAG, "download file http path:" + downloadUrl);

123                 URLConnection conn = url.openConnection();

124                 // 读取下载文件总大小

125                 int fileSize = conn.getContentLength();

126                 if (fileSize <= 0) {

127                     System.out.println("读取文件失败");

128                     return;

129                 }

130                 // 设置ProgressBar最大的长度为文件Size

131                 mProgressbar.setMax(fileSize);

132 

133                 // 计算每条线程下载的数据长度

134                 blockSize = (fileSize % threadNum) == 0 ? fileSize / threadNum

135                         : fileSize / threadNum + 1;

136 

137                 Log.d(TAG, "fileSize:" + fileSize + "  blockSize:");

138 

139                 File file = new File(filePath);

140                 for (int i = 0; i < threads.length; i++) {

141                     // 启动线程，分别下载每个线程需要下载的部分

142                     threads[i] = new FileDownloadThread(url, file, blockSize,

143                             (i + 1));

144                     threads[i].setName("Thread:" + i);

145                     threads[i].start();

146                 }

147 

148                 boolean isfinished = false;

149                 int downloadedAllSize = 0;

150                 while (!isfinished) {

151                     isfinished = true;

152                     // 当前所有线程下载总量

153                     downloadedAllSize = 0;

154                     for (int i = 0; i < threads.length; i++) {

155                         downloadedAllSize += threads[i].getDownloadLength();

156                         if (!threads[i].isCompleted()) {

157                             isfinished = false;

158                         }

159                     }

160                     // 通知handler去更新视图组件

161                     Message msg = new Message();

162                     msg.getData().putInt("size", downloadedAllSize);

163                     mHandler.sendMessage(msg);

164                     // Log.d(TAG, "current downloadSize:" + downloadedAllSize);

165                     Thread.sleep(1000);// 休息1秒后再读取下载进度

166                 }

167                 Log.d(TAG, " all of downloadSize:" + downloadedAllSize);

168 

169             } catch (MalformedURLException e) {

170                 e.printStackTrace();

171             } catch (IOException e) {

172                 e.printStackTrace();

173             } catch (InterruptedException e) {

174                 e.printStackTrace();

175             }

176 

177         }

178     }

179 

180 }

FileDownloadThread:

  1 package com.amos.app;

  2 

  3 import java.io.BufferedInputStream;

  4 import java.io.File;

  5 import java.io.IOException;

  6 import java.io.RandomAccessFile;

  7 import java.net.URL;

  8 import java.net.URLConnection;

  9 import android.util.Log;

 10 

 11 /**

 12  * 文件下载类

 13  * 

 14  * @author yangxiaolong

 15  * @2014-5-6

 16  */

 17 public class FileDownloadThread extends Thread {

 18 

 19     private static final String TAG = FileDownloadThread.class.getSimpleName();

 20 

 21     /** 当前下载是否完成 */

 22     private boolean isCompleted = false;

 23     /** 当前下载文件长度 */

 24     private int downloadLength = 0;

 25     /** 文件保存路径 */

 26     private File file;

 27     /** 文件下载路径 */

 28     private URL downloadUrl;

 29     /** 当前下载线程ID */

 30     private int threadId;

 31     /** 线程下载数据长度 */

 32     private int blockSize;

 33 

 34     /**

 35      * 

 36      * @param url:文件下载地址

 37      * @param file:文件保存路径

 38      * @param blocksize:下载数据长度

 39      * @param threadId:线程ID

 40      */

 41     public FileDownloadThread(URL downloadUrl, File file, int blocksize,

 42             int threadId) {

 43         this.downloadUrl = downloadUrl;

 44         this.file = file;

 45         this.threadId = threadId;

 46         this.blockSize = blocksize;

 47     }

 48 

 49     @Override

 50     public void run() {

 51 

 52         BufferedInputStream bis = null;

 53         RandomAccessFile raf = null;

 54 

 55         try {

 56             URLConnection conn = downloadUrl.openConnection();

 57             conn.setAllowUserInteraction(true);

 58 

 59             int startPos = blockSize * (threadId - 1);//开始位置

 60             int endPos = blockSize * threadId - 1;//结束位置

 61             //设置当前线程下载的起点、终点

 62             conn.setRequestProperty("Range", "bytes=" + startPos + "-" + endPos);

 63             System.out.println(Thread.currentThread().getName() + "  bytes="

 64                     + startPos + "-" + endPos);

 65 

 66             byte[] buffer = new byte[1024];

 67             bis = new BufferedInputStream(conn.getInputStream());

 68 

 69             raf = new RandomAccessFile(file, "rwd");

 70             raf.seek(startPos);

 71             int len;

 72             while ((len = bis.read(buffer, 0, 1024)) != -1) {

 73                 raf.write(buffer, 0, len);

 74                 downloadLength += len;

 75             }

 76             isCompleted = true;

 77             Log.d(TAG, "current thread task has finished,all size:"

 78                     + downloadLength);

 79 

 80         } catch (IOException e) {

 81             e.printStackTrace();

 82         } finally {

 83             if (bis != null) {

 84                 try {

 85                     bis.close();

 86                 } catch (IOException e) {

 87                     e.printStackTrace();

 88                 }

 89             }

 90             if (raf != null) {

 91                 try {

 92                     raf.close();

 93                 } catch (IOException e) {

 94                     e.printStackTrace();

 95                 }

 96             }

 97         }

 98     }

 99 

100     /**

101      * 线程文件是否下载完毕

102      */

103     public boolean isCompleted() {

104         return isCompleted;

105     }

106 

107     /**

108      * 线程下载文件长度

109      */

110     public int getDownloadLength() {

111         return downloadLength;

112     }

113 

114 }

补充:.xml文件：

 1 <?xml version="1.0" encoding="utf-8"?>

 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

 3     android:layout_width="match_parent"

 4     android:layout_height="match_parent"

 5     android:background="@android:color/white"

 6     android:orientation="vertical" >

 7 

 8     <Button

 9         android:id="@+id/download_btn"

10         android:layout_width="match_parent"

11         android:layout_height="60dp"

12         android:layout_gravity="center"

13         android:layout_marginLeft="10dp"

14         android:layout_marginRight="10dp"

15         android:layout_marginTop="50dp"

16         android:text="Download"

17         android:textSize="18sp" />

18 

19     <ProgressBar

20         android:id="@+id/download_progress"

21         style="?android:attr/progressBarStyleHorizontal"

22         android:layout_width="fill_parent"

23         android:layout_height="wrap_content"

24         android:layout_marginLeft="10dip"

25         android:layout_marginRight="10dip"

26         android:layout_marginTop="20dp"

27         android:indeterminate="false"

28         android:max="100" />

29 

30     <TextView

31         android:id="@+id/download_message"

32         android:layout_width="wrap_content"

33         android:layout_height="wrap_content"

34         android:layout_gravity="center"

35         android:layout_marginTop="10dp"

36         android:maxLines="1"

37         android:text="50%"

38         android:textSize="18dip" />

39 

40 </LinearLayout>

 

效果图：