android多线程断点下载

很多时候我们需要在Android设备上下载远程服务器上的文件进安装，前两天晚上我看到一个视频，写了两个晚上，大概理解一下。   直接通过Android提供的Http类访问远程服务器，这里AndroidHttpClient是SDK 2.2中新出的方法，
下载断点文件。
下面让我们看一下图先。
 

让我们看一下代码的实现方法。
package com.smart.db;
import java.util.HashMap;
import java.util.Map;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
/**
* 业务bean
*
*/
public class FileService {
private DBOpenHelper openHelper;
public FileService(Context context) {
  openHelper = new DBOpenHelper(context);
}
/**
  * 获取每条线程已经下载的文件长度
  * @param path
  * @return
  */
public Map<Integer, Integer> getData(String path){
  SQLiteDatabase db = openHelper.getReadableDatabase();
  Cursor cursor = db.rawQuery("select threadid, downlength from SmartFileDownlog where downpath=?", new String[]{path});
  Map<Integer, Integer> data = new HashMap<Integer, Integer>();
  while(cursor.moveToNext()){
   data.put(cursor.getInt(0), cursor.getInt(1));
  }
  cursor.close();
  db.close();
  return data;
}
/**
  * 保存每条线程已经下载的文件长度
  * @param path
  * @param map
  */
public void save(String path,  Map<Integer, Integer> map){//int threadid, int position
  SQLiteDatabase db = openHelper.getWritableDatabase();
  db.beginTransaction();
  try{
   for(Map.Entry<Integer, Integer> entry : map.entrySet()){
    db.execSQL("insert into SmartFileDownlog(downpath, threadid, downlength) values(?,?,?)",
      new Object[]{path, entry.getKey(), entry.getValue()});
   }
   db.setTransactionSuccessful();
  }finally{
   db.endTransaction();
  }
  db.close();
}
/**
  * 实时更新每条线程已经下载的文件长度
  * @param path
  * @param map
  */
public void update(String path, Map<Integer, Integer> map){
  SQLiteDatabase db = openHelper.getWritableDatabase();
  db.beginTransaction();
  try{
   for(Map.Entry<Integer, Integer> entry : map.entrySet()){
    db.execSQL("update SmartFileDownlog set downlength=? where downpath=? and threadid=?",
      new Object[]{entry.getValue(), path, entry.getKey()});
   }
   db.setTransactionSuccessful();
  }finally{
   db.endTransaction();
  }
  db.close();
}
/**
  * 当文件下载完成后，删除对应的下载记录
  * @param path
  */
public void delete(String path){
  SQLiteDatabase db = openHelper.getWritableDatabase();
  db.execSQL("delete from SmartFileDownlog where downpath=?", new Object[]{path});
  db.close();
}

}


package com.smart.impl;
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 android.content.Context;
import android.util.Log;
import com.smart.db.FileService;
/**
* 文件下载器
* @author [email protected]
*/
public class SmartFileDownloader {
private static final String TAG = "SmartFileDownloader";
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 SmartDownloadThread[] 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 void update(int threadId, int pos) {
  this.data.put(threadId, pos);
}
/**
  * 保存记录文件
  */
protected synchronized void saveLogFile() {
  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 SmartFileDownloader(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 SmartDownloadThread[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);
    this.saveFile = new File(fileSaveDir, filename);/* 保存文件 */
    Map<Integer, Integer> logdata = fileService.getData(downloadUrl);
    if(logdata.size()>0){
     for(Map.Entry<Integer, Integer> entry : logdata.entrySet())
      data.put(entry.getKey(), entry.getValue());
    }
    this.block = (this.fileSize % this.threads.length)==0? this.fileSize / this.threads.length : this.fileSize / this.threads.length + 1;
    if(this.data.size()==this.threads.length){
     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);
    }    
   }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(SmartDownloadProgressListener 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();//清除数据
    for (int i = 0; i < this.threads.length; i++) {
     this.data.put(i+1, 0);
    }
   }
   for (int i = 0; i < this.threads.length; i++) {
    int downLength = this.data.get(i+1);
    if(downLength < this.block && this.downloadSize<this.fileSize){ //该线程未完成下载时,继续下载      
     this.threads = new SmartDownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
     this.threads.setPriority(7);
     this.threads.start();
    }else{
     this.threads = null;
    }
   }
   this.fileService.save(this.downloadUrl, this.data);
   boolean notFinish = true;//下载未完成
   while (notFinish) {// 循环判断是否下载完毕
    Thread.sleep(900);
    notFinish = false;//假定下载完成
    for (int i = 0; i < this.threads.length; i++){
     if (this.threads != null && !this.threads.isFinish()) {
      notFinish = true;//下载没有完成
      if(this.threads.getDownLength() == -1){//如果下载失败,再重新下载
       this.threads = new SmartDownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
       this.threads.setPriority(7);
       this.threads.start();
      }
     }
    }    
    if(listener!=null) listener.onDownloadSize(this.downloadSize);
   }
   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());
  }
}
//打印日志
private static void print(String msg){
  Log.i(TAG, msg);
}


}
package com.smart.impl;
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 SmartDownloadThread extends Thread {
private static final String TAG = "SmartDownloadThread";
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 SmartFileDownloader downloader;
public SmartDownloadThread(SmartFileDownloader 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.saveLogFile();
     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;
}
}
package com.smart.activoty.download;
import java.io.File;
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;
import com.smart.impl.SmartDownloadProgressListener;
import com.smart.impl.SmartFileDownloader;
public class SmartDownloadActivity extends Activity {
    private ProgressBar downloadbar;
    private EditText pathText;
    private TextView resultView;
    private Handler handler = new Handler(){
  @Override//信息
  public void handleMessage(Message msg) {
   switch (msg.what) {
   case 1:
    int size = msg.getData().getInt("size");
    downloadbar.setProgress(size);
    float result = (float)downloadbar.getProgress()/ (float)downloadbar.getMax();
    int p = (int)(result*100);
    resultView.setText(p+"%");
    if(downloadbar.getProgress()==downloadbar.getMax())
     Toast.makeText(SmartDownloadActivity.this, R.string.success, 1).show();
    break;
   case -1:
    Toast.makeText(SmartDownloadActivity.this, R.string.error, 1).show();
    break;
   }
   
  }     
    };
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        Button button = (Button)this.findViewById(R.id.button);
        downloadbar = (ProgressBar)this.findViewById(R.id.downloadbar);
        pathText = (EditText)this.findViewById(R.id.path);
        resultView = (TextView)this.findViewById(R.id.result);
        button.setOnClickListener(new View.OnClickListener() {   
   @Override
   public void onClick(View v) {
    String path = pathText.getText().toString();
    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
     File dir = Environment.getExternalStorageDirectory();//文件保存目录
     download(path, dir);
    }else{
     Toast.makeText(SmartDownloadActivity.this, R.string.sdcarderror, 1).show();
    }
   }
  });
    }
    //对于UI控件的更新只能由主线程(UI线程)负责，如果在非UI线程更新UI控件，更新的结果不会反映在屏幕上，某些控件还会出错
    private void download(final String path, final File dir){
     new Thread(new Runnable() {
   @Override
   public void run() {
    try {
     SmartFileDownloader loader = new SmartFileDownloader(SmartDownloadActivity.this, path, dir, 3);
     int length = loader.getFileSize();//获取文件的长度
     downloadbar.setMax(length);
     loader.download(new SmartDownloadProgressListener(){
      @Override
      public void onDownloadSize(int size) {//可以实时得到文件下载的长度
       Message msg = new Message();
       msg.what = 1;
       msg.getData().putInt("size", size);       
       handler.sendMessage(msg);
      }});
    } catch (Exception e) {
     Message msg = new Message();//信息提示
     msg.what = -1;
     msg.getData().putString("error", "下载失败");//如果下载错误，显示提示失败！
     handler.sendMessage(msg);
    }
   }
  }).start();//开始
     
    }
}