你的位置:首页 > Java教程

[Java教程]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 yangxiaolong102    * @2014-8-7103   */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     @Override117     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Size131         mProgressbar.setMax(fileSize);132 133         // 计算每条线程下载的数据长度134         blockSize = (fileSize % threadNum) == 0 ? fileSize / threadNum135             : 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:.

 1 <? 2 <LinearLayout  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   <ProgressBar20     android:id="@+id/download_progress"21     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   <TextView31     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: