android--http协议多线程断点续传下载的实现

看注释理解断点续传下载代码！！！！

0.使用多线程下载会提升文件下载的速度，那么多线程下载文件的过程是：

(1)首先获得下载文件的长度，然后设置本地文件的长度

    HttpURLConnection.getContentLength();

    RandomAccessFile file = new RandomAccessFile("QQWubiSetup.exe","rwd");

    file.setLength(filesize);//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=?

(3)使用Http的Range头字段指定每条线程从文件的什么位置开始下载，下载到什么位置为止，

     如：指定从文件的2M位置开始下载，下载到位置(4M-1byte)为止

    代码如下：HttpURLConnection.setRequestProperty("Range", "bytes=2097152-4194303");

(4)保存文件，使用RandomAccessFile类指定每条线程从本地文件的什么位置开始写入数据。

RandomAccessFile threadfile = new RandomAccessFile("QQWubiSetup.exe ","rwd");

threadfile.seek(2097152);//从文件的什么位置开始写入数据

 

 

2,。下载器

package cn.itcast.net.download;

import java.io.File;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import cn.itcast.service.FileService;

import android.content.Context;
import android.util.Log;
/**
 * 文件下载器
 * FileDownloader loader = new FileDownloader(context, "http://browse.babasport.com/ejb3/ActivePort.exe",
    new File("D:\\androidsoft\\test"), 2);
  loader.getFileSize();//得到文件总大小
  try {
   loader.download(new DownloadProgressListener(){
    public void onDownloadSize(int size) {
     print("已经下载："+ size);
    }   
   });
  } catch (Exception e) {
   e.printStackTrace();
  }
 */
public class FileDownloader {
 private static final String TAG = "FileDownloader";
 private Context context;
 private FileService fileService; 
 /* 已下载文件长度 */
 private int downloadSize = 0;
 /* 原始文件长度 */
 private int fileSize = 0;
 /* 线程数 */
 private DownloadThread[] threads;
 /* 本地保存文件 */
 private File saveFile;
 /* 缓存各线程下载的长度*/
 private Map<Integer, Integer> data = new ConcurrentHashMap<Integer, Integer>();
 /* 每条线程下载的长度 */
 private int block;
 /* 下载路径  */
 private String downloadUrl;
 /**
  * 获取线程数
  */
 public int getThreadSize() {
  return threads.length;
 }
 /**
  * 获取文件大小
  * @return
  */
 public int getFileSize() {
  return fileSize;
 }
 /**
  * 累计已下载大小
  * @param size
  */
 protected synchronized void append(int size) {
  downloadSize += size;
 }
 /**
  * 更新指定线程最后下载的位置
  * @param threadId 线程id
  * @param pos 最后下载的位置
  */
 protected synchronized void update(int threadId, int pos) {
  this.data.put(threadId, pos);
  this.fileService.update(this.downloadUrl, this.data);
 }
 /**
  * 构建文件下载器
  * @param downloadUrl 下载路径
  * @param fileSaveDir 文件保存目录
  * @param threadNum 下载线程数
  */
 public FileDownloader(Context context, String downloadUrl, File fileSaveDir, int threadNum) {
  try {
   this.context = context;
   this.downloadUrl = downloadUrl;
   fileService = new FileService(this.context);
   URL url = new URL(this.downloadUrl);
   if(!fileSaveDir.exists()) fileSaveDir.mkdirs();
   this.threads = new DownloadThread[threadNum];     
   HttpURLConnection conn = (HttpURLConnection) url.openConnection();
   conn.setConnectTimeout(5*1000);
   conn.setRequestMethod("GET");
   conn.setRequestProperty("Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
   conn.setRequestProperty("Accept-Language", "zh-CN");
   conn.setRequestProperty("Referer", downloadUrl);
   conn.setRequestProperty("Charset", "UTF-8");
   conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
   conn.setRequestProperty("Connection", "Keep-Alive");
   conn.connect();
   printResponseHeader(conn);
   if (conn.getResponseCode()==200) {
    this.fileSize = conn.getContentLength();//根据响应获取文件大小
    if (this.fileSize <= 0) throw new RuntimeException("Unkown file size ");
      
    String filename = getFileName(conn);//获取文件名称
    this.saveFile = new File(fileSaveDir, filename);//构建保存文件
    Map<Integer, Integer> logdata = fileService.getData(downloadUrl);//获取下载记录
    if(logdata.size()>0){//如果存在下载记录
     for(Map.Entry<Integer, Integer> entry : logdata.entrySet())
      data.put(entry.getKey(), entry.getValue());//把各条线程已经下载的数据长度放入data中
    }
    if(this.data.size()==this.threads.length){//下面计算所有线程已经下载的数据长度
     for (int i = 0; i < this.threads.length; i++) {
      this.downloadSize += this.data.get(i+1);
     }
     print("已经下载的长度"+ this.downloadSize);
    }
    //计算每条线程下载的数据长度
    this.block = (this.fileSize % this.threads.length)==0? this.fileSize / this.threads.length : this.fileSize / this.threads.length + 1;
   }else{
    throw new RuntimeException("server no response ");
   }
  } catch (Exception e) {
   print(e.toString());
   throw new RuntimeException("don't connection this url");
  }
 }
 /**
  * 获取文件名
  */
 private String getFileName(HttpURLConnection conn) {
  String filename = this.downloadUrl.substring(this.downloadUrl.lastIndexOf('/') + 1);
  if(filename==null || "".equals(filename.trim())){//如果获取不到文件名称
   for (int i = 0;; i++) {
    String mine = conn.getHeaderField(i);
    if (mine == null) break;
    if("content-disposition".equals(conn.getHeaderFieldKey(i).toLowerCase())){
     Matcher m = Pattern.compile(".*filename=(.*)").matcher(mine.toLowerCase());
     if(m.find()) return m.group(1);
    }
   }
   filename = UUID.randomUUID()+ ".tmp";//默认取一个文件名
  }
  return filename;
 }
 
 /**
  *  开始下载文件
  * @param listener 监听下载数量的变化,如果不需要了解实时下载的数量,可以设置为null
  * @return 已下载文件大小
  * @throws Exception
  */
 public int download(DownloadProgressListener listener) throws Exception{
  try {
   RandomAccessFile randOut = new RandomAccessFile(this.saveFile, "rw");
   if(this.fileSize>0) randOut.setLength(this.fileSize);
   randOut.close();
   URL url = new URL(this.downloadUrl);
   if(this.data.size() != this.threads.length){
    this.data.clear();
    for (int i = 0; i < this.threads.length; i++) {
     this.data.put(i+1, 0);//初始化每条线程已经下载的数据长度为0
    }
   }
   for (int i = 0; i < this.threads.length; i++) {//开启线程进行下载
    int downLength = this.data.get(i+1);
    if(downLength < this.block && this.downloadSize<this.fileSize){//判断线程是否已经完成下载,否则继续下载 
     this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
     this.threads[i].setPriority(7);
     this.threads[i].start();
    }else{
     this.threads[i] = null;
    }
   }
   this.fileService.save(this.downloadUrl, this.data);
   boolean notFinish = true;//下载未完成
   while (notFinish) {// 循环判断所有线程是否完成下载
    Thread.sleep(900);
    notFinish = false;//假定全部线程下载完成
    for (int i = 0; i < this.threads.length; i++){
     if (this.threads[i] != null && !this.threads[i].isFinish()) {//如果发现线程未完成下载
      notFinish = true;//设置标志为下载没有完成
      if(this.threads[i].getDownLength() == -1){//如果下载失败,再重新下载
       this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
       this.threads[i].setPriority(7);
       this.threads[i].start();
      }
     }
    }    
    if(listener!=null) listener.onDownloadSize(this.downloadSize);//通知目前已经下载完成的数据长度
   }
   fileService.delete(this.downloadUrl);
  } catch (Exception e) {
   print(e.toString());
   throw new Exception("file download fail");
  }
  return this.downloadSize;
 }
 /**
  * 获取Http响应头字段
  * @param http
  * @return
  */
 public static Map<String, String> getHttpResponseHeader(HttpURLConnection http) {
  Map<String, String> header = new LinkedHashMap<String, String>();
  for (int i = 0;; i++) {
   String mine = http.getHeaderField(i);
   if (mine == null) break;
   header.put(http.getHeaderFieldKey(i), mine);
  }
  return header;
 }
 /**
  * 打印Http头字段
  * @param http
  */
 public static void printResponseHeader(HttpURLConnection http){
  Map<String, String> header = getHttpResponseHeader(http);
  for(Map.Entry<String, String> entry : header.entrySet()){
   String key = entry.getKey()!=null ? entry.getKey()+ ":" : "";
   print(key+ entry.getValue());
  }
 }

 private static void print(String msg){
  Log.i(TAG, msg);
 }
}

 

下载线程代码;

package cn.itcast.net.download;

import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;

import android.util.Log;

public class DownloadThread extends Thread {
 private static final String TAG = "DownloadThread";
 private File saveFile;
 private URL downUrl;
 private int block;
 /* 下载开始位置  */
 private int threadId = -1; 
 private int downLength;
 private boolean finish = false;
 private FileDownloader downloader;

 public DownloadThread(FileDownloader downloader, URL downUrl, File saveFile, int block, int downLength, int threadId) {
  this.downUrl = downUrl;
  this.saveFile = saveFile;
  this.block = block;
  this.downloader = downloader;
  this.threadId = threadId;
  this.downLength = downLength;
 }
 
 @Override
 public void run() {
  if(downLength < block){//未下载完成
   try {
    HttpURLConnection http = (HttpURLConnection) downUrl.openConnection();
    http.setConnectTimeout(5 * 1000);
    http.setRequestMethod("GET");
    http.setRequestProperty("Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
    http.setRequestProperty("Accept-Language", "zh-CN");
    http.setRequestProperty("Referer", downUrl.toString());
    http.setRequestProperty("Charset", "UTF-8");
    int startPos = block * (threadId - 1) + downLength;//开始位置
    int endPos = block * threadId -1;//结束位置
    http.setRequestProperty("Range", "bytes=" + startPos + "-"+ endPos);//设置获取实体数据的范围
    http.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
    http.setRequestProperty("Connection", "Keep-Alive");
    
    InputStream inStream = http.getInputStream();
    byte[] buffer = new byte[1024];
    int offset = 0;
    print("Thread " + this.threadId + " start download from position "+ startPos);
    RandomAccessFile threadfile = new RandomAccessFile(this.saveFile, "rwd");
    threadfile.seek(startPos);
    while ((offset = inStream.read(buffer, 0, 1024)) != -1) {
     threadfile.write(buffer, 0, offset);
     downLength += offset;
     downloader.update(this.threadId, downLength);
     downloader.append(offset);
    }
    threadfile.close();
    inStream.close();
    print("Thread " + this.threadId + " download finish");
    this.finish = true;
   } catch (Exception e) {
    this.downLength = -1;
    print("Thread "+ this.threadId+ ":"+ e);
   }
  }
 }
 private static void print(String msg){
  Log.i(TAG, msg);
 }
 /**
  * 下载是否完成
  * @return
  */
 public boolean isFinish() {
  return finish;
 }
 /**
  * 已经下载的内容大小
  * @return 如果返回值为-1,代表下载失败
  */
 public long getDownLength() {
  return downLength;
 }
}

实时监听下载进度接口：

package cn.itcast.net.download;

public interface DownloadProgressListener {
 public void onDownloadSize(int size);
}

 

主Activity，关键点使用Handler更新进度条与开启线程下载避免ANR

若不使用Handler却要立即更新进度条数据，可使用：

//resultView.invalidate(); UI线程中立即更新进度条方法

//resultView.postInvalidate(); 非UI线程中立即更新进度条方法

package cn.itcast.download;

import java.io.File;

import cn.itcast.net.download.DownloadProgressListener;
import cn.itcast.net.download.FileDownloader;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

public class DownloadActivity extends Activity {
    private EditText downloadpathText;
    private TextView resultView;
    private ProgressBar progressBar;
    //当Handler被创建会关联到创建它的当前线程的消息队列，该类用于往消息队列发送消息
    //消息队列中的消息由当前线程内部进行处理
    private Handler handler = new Handler(){

  @Override
  public void handleMessage(Message msg) {   
   switch (msg.what) {
   case 1:    
    progressBar.setProgress(msg.getData().getInt("size"));
    float num = (float)progressBar.getProgress()/(float)progressBar.getMax();
    int result = (int)(num*100);
    resultView.setText(result+ "%");
    if(progressBar.getProgress()==progressBar.getMax()){
     Toast.makeText(DownloadActivity.this, R.string.success, 1).show();
    }
    break;

   case -1:
    Toast.makeText(DownloadActivity.this, R.string.error, 1).show();
    break;
   }
  }
    };
   
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
       
        downloadpathText = (EditText) this.findViewById(R.id.downloadpath);
        progressBar = (ProgressBar) this.findViewById(R.id.downloadbar);
        resultView = (TextView) this.findViewById(R.id.result);
        Button button = (Button) this.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {   
   @Override
   public void onClick(View v) {
    String path = downloadpathText.getText().toString();
    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
     download(path, Environment.getExternalStorageDirectory());
    }else{
     Toast.makeText(DownloadActivity.this, R.string.sdcarderror, 1).show();
    }
    
   }
  });
    }
    //主线程(UI线程)
    //业务逻辑正确，但是该程序运行的时候有问题
    //对于显示控件的界面更新只是由UI线程负责，如果是在非UI线程更新控件的属性值，更新后的显示界面不会反映到屏幕上
    private void download(final String path, final File savedir) {
     new Thread(new Runnable() {   
   @Override
   public void run() {
    FileDownloader loader = new FileDownloader(DownloadActivity.this, path, savedir, 4);
       progressBar.setMax(loader.getFileSize());//设置进度条的最大刻度为文件的长度
    try {
     loader.download(new DownloadProgressListener() {
      @Override
      public void onDownloadSize(int size) {//实时获知文件已经下载的数据长度
       Message msg = new Message();
       msg.what = 1;
       msg.getData().putInt("size", size);
       handler.sendMessage(msg);//发送消息
      }
     });
    } catch (Exception e) {
     handler.obtainMessage(-1).sendToTarget();
    }
   }
  }).start();
 }
}