android实现断点续传

代码如下:

package com.example.downloaderstopsart;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.os.StrictMode;import android.app.ListActivity;import android.view.View;import android.widget.LinearLayout;import android.widget.LinearLayout.LayoutParams;import android.widget.ProgressBar;import android.widget.SimpleAdapter;import android.widget.TextView;import android.widget.Toast;public class MainActivity extends ListActivity  {     // 固定下载的资源路径，这里可以设置网络上的地址      private static final String URL = "http://10.81.36.193:8080/";      // 固定存放下载的音乐的路径：SD卡目录下      private static final String SD_PATH = "/mnt/sdcard/";      // 存放各个下载器      private Map<String, Downloader> downloaders = new HashMap<String, Downloader>();      // 存放与下载器对应的进度条      private Map<String, ProgressBar> ProgressBars = new HashMap<String, ProgressBar>();      /**       * 利用消息处理机制适时更新进度条       */      private Handler mHandler = new Handler() {          public void handleMessage(Message msg) {              if (msg.what == 1) {                  String url = (String) msg.obj;                  int length = msg.arg1;                  ProgressBar bar = ProgressBars.get(url);                  if (bar != null) {                      // 设置进度条按读取的length长度更新                      bar.incrementProgressBy(length);                      if (bar.getProgress() == bar.getMax()) {                          Toast.makeText(MainActivity.this, "下载完成！", 0).show();                          // 下载完成后清除进度条并将map中的数据清空                          LinearLayout layout = (LinearLayout) bar.getParent();                          layout.removeView(bar);                          ProgressBars.remove(url);                          downloaders.get(url).delete(url);                          downloaders.get(url).reset();                          downloaders.remove(url);                      }                  }              }          }      };      @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);          showListView();          StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectDiskReads().detectDiskWrites().detectNetwork().penaltyLog().build());        StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder().detectLeakedSqlLiteObjects().detectLeakedClosableObjects().penaltyLog().penaltyDeath().build());      }      // 显示listView，这里可以随便添加音乐      private void showListView() {          List<Map<String, String>> data = new ArrayList<Map<String, String>>();          Map<String, String> map = new HashMap<String, String>();          map.put("name", "mm.mp3");          data.add(map);          map = new HashMap<String, String>();          map.put("name", "pp.mp3");          data.add(map);          map = new HashMap<String, String>();          map.put("name", "tt.mp3");          data.add(map);          map = new HashMap<String, String>();          map.put("name", "ou.mp3");          data.add(map);          SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.list_item, new String[] { "name" },                  new int[] { R.id.tv_resouce_name });          setListAdapter(adapter);      }      /**       * 响应开始下载按钮的点击事件       */      public void startDownload(View v) {          // 得到textView的内容          LinearLayout layout = (LinearLayout) v.getParent();          String musicName = ((TextView) layout.findViewById(R.id.tv_resouce_name)).getText().toString();          String urlstr = URL + musicName;          String localfile = SD_PATH + musicName;          //设置下载线程数为4，这里是我为了方便随便固定的          int threadcount = 4;          // 初始化一个downloader下载器          Downloader downloader = downloaders.get(urlstr);          if (downloader == null) {              downloader = new Downloader(urlstr, localfile, threadcount, this, mHandler);              downloaders.put(urlstr, downloader);          }          if (downloader.isdownloading())             return;         // 得到下载信息类的个数组成集合         LoadInfo loadInfo = downloader.getDownloaderInfors();         // 显示进度条         showProgress(loadInfo, urlstr, v);         // 调用方法开始下载         downloader.download();     }     /**      * 显示进度条      */     private void showProgress(LoadInfo loadInfo, String url, View v) {         ProgressBar bar = ProgressBars.get(url);         if (bar == null) {             bar = new ProgressBar(this, null, android.R.attr.progressBarStyleHorizontal);             bar.setMax(loadInfo.getFileSize());             bar.setProgress(loadInfo.getComplete());             ProgressBars.put(url, bar);             LinearLayout.LayoutParams params = new LayoutParams(LayoutParams.FILL_PARENT, 5);             ((LinearLayout) ((LinearLayout) v.getParent()).getParent()).addView(bar, params);         }     }     /**      * 响应暂停下载按钮的点击事件      */     public void pauseDownload(View v) {         LinearLayout layout = (LinearLayout) v.getParent();         String musicName = ((TextView) layout.findViewById(R.id.tv_resouce_name)).getText().toString();         String urlstr = URL + musicName;         downloaders.get(urlstr).pause();     } }

DBHelper：

package com.example.downloaderstopsart;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;/** * 建立一个数据库帮助类 */public class DBHelper extends SQLiteOpenHelper {// download.db-->数据库名public DBHelper(Context context) {super(context, "download.db", null, 1);}/** * 在download.db数据库下创建一个download_info表存储下载信息 */@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL("create table download_info(_id integer PRIMARY KEY AUTOINCREMENT, thread_id integer, "+ "start_pos integer, end_pos integer, compelete_size integer,url char)");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}}

DownloadInfo：

package com.example.downloaderstopsart;public class DownloadInfo {private int threadId;// 下载器idprivate int startPos;// 开始点private int endPos;// 结束点private int compeleteSize;// 完成度private String url;// 下载器网络标识public DownloadInfo(int threadId, int startPos, int endPos,int compeleteSize, String url) {this.threadId = threadId;this.startPos = startPos;this.endPos = endPos;this.compeleteSize = compeleteSize;this.url = url;}public DownloadInfo() {}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public int getThreadId() {return threadId;}public void setThreadId(int threadId) {this.threadId = threadId;}public int getStartPos() {return startPos;}public void setStartPos(int startPos) {this.startPos = startPos;}public int getEndPos() {return endPos;}public void setEndPos(int endPos) {this.endPos = endPos;}public int getCompeleteSize() {return compeleteSize;}public void setCompeleteSize(int compeleteSize) {this.compeleteSize = compeleteSize;}@Overridepublic String toString() {return "DownloadInfo [threadId=" + threadId + ", startPos=" + startPos+ ", endPos=" + endPos + ", compeleteSize=" + compeleteSize+ "]";}}

LoadInfo：

package com.example.downloaderstopsart;public class LoadInfo {public int fileSize;// 文件大小private int complete;// 完成度private String urlstring;// 下载器标识public LoadInfo(int fileSize, int complete, String urlstring) {this.fileSize = fileSize;this.complete = complete;this.urlstring = urlstring;}public LoadInfo() {}public int getFileSize() {return fileSize;}public void setFileSize(int fileSize) {this.fileSize = fileSize;}public int getComplete() {return complete;}public void setComplete(int complete) {this.complete = complete;}public String getUrlstring() {return urlstring;}public void setUrlstring(String urlstring) {this.urlstring = urlstring;}@Overridepublic String toString() {return "LoadInfo [fileSize=" + fileSize + ", complete=" + complete+ ", urlstring=" + urlstring + "]";}}

Downloader：

package com.example.downloaderstopsart;import java.io.File;import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; import java.util.ArrayList; import java.util.List; import android.content.Context; import android.os.Handler; import android.os.Message; import android.util.Log; public class Downloader {     private String urlstr;// 下载的地址     private String localfile;// 保存路径     private int threadcount;// 线程数     private Handler mHandler;// 消息处理器     private Dao dao;// 工具类     private int fileSize;// 所要下载的文件的大小     private List<DownloadInfo> infos;// 存放下载信息类的集合     private static final int INIT = 1;//定义三种下载的状态：初始化状态，正在下载状态，暂停状态     private static final int DOWNLOADING = 2;     private static final int PAUSE = 3;     private int state = INIT;     public Downloader(String urlstr, String localfile, int threadcount,             Context context, Handler mHandler) {         this.urlstr = urlstr;         this.localfile = localfile;         this.threadcount = threadcount;         this.mHandler = mHandler;         dao = new Dao(context);     }     /**      *判断是否正在下载      */     public boolean isdownloading() {         return state == DOWNLOADING;     }     /**      * 得到downloader里的信息      * 首先进行判断是否是第一次下载，如果是第一次就要进行初始化，并将下载器的信息保存到数据库中      * 如果不是第一次下载，那就要从数据库中读出之前下载的信息（起始位置，结束为止，文件大小等），并将下载信息返回给下载器      */     public LoadInfo getDownloaderInfors() {         if (isFirst(urlstr)) {             Log.v("TAG", "isFirst");             init();             int range = fileSize / threadcount;             infos = new ArrayList<DownloadInfo>();             for (int i = 0; i < threadcount - 1; i++) {                 DownloadInfo info = new DownloadInfo(i, i * range, (i + 1)* range - 1, 0, urlstr);                 infos.add(info);             }             DownloadInfo info = new DownloadInfo(threadcount - 1,(threadcount - 1) * range, fileSize - 1, 0, urlstr);             infos.add(info);             //保存infos中的数据到数据库             dao.saveInfos(infos);             //创建一个LoadInfo对象记载下载器的具体信息             LoadInfo loadInfo = new LoadInfo(fileSize, 0, urlstr);             return loadInfo;         } else {             //得到数据库中已有的urlstr的下载器的具体信息             infos = dao.getInfos(urlstr);             Log.v("TAG", "not isFirst size=" + infos.size());             int size = 0;             int compeleteSize = 0;             for (DownloadInfo info : infos) {                 compeleteSize += info.getCompeleteSize();                 size += info.getEndPos() - info.getStartPos() + 1;             }             return new LoadInfo(size, compeleteSize, urlstr);         }     }     /**      * 初始化      */     private void init() {         try {             URL url = new URL(urlstr);             HttpURLConnection connection = (HttpURLConnection) url.openConnection();             connection.setConnectTimeout(5000);             connection.setRequestMethod("GET");             fileSize = connection.getContentLength();             File file = new File(localfile);             if (!file.exists()) {                 file.createNewFile();             }             // 本地访问文件             RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");             accessFile.setLength(fileSize);             accessFile.close();             connection.disconnect();         } catch (Exception e) {             e.printStackTrace();         }     }     /**      * 判断是否是第一次 下载      */     private boolean isFirst(String urlstr) {         return dao.isHasInfors(urlstr);     }     /**      * 利用线程开始下载数据      */     public void download() {         if (infos != null) {             if (state == DOWNLOADING)                 return;             state = DOWNLOADING;             for (DownloadInfo info : infos) {                 new MyThread(info.getThreadId(), info.getStartPos(),                         info.getEndPos(), info.getCompeleteSize(),                         info.getUrl()).start();             }         }     }     public class MyThread extends Thread {         private int threadId;         private int startPos;         private int endPos;         private int compeleteSize;         private String urlstr;         public MyThread(int threadId, int startPos, int endPos,                 int compeleteSize, String urlstr) {             this.threadId = threadId;             this.startPos = startPos;             this.endPos = endPos;             this.compeleteSize = compeleteSize;             this.urlstr = urlstr;         }         @Override         public void run() {             HttpURLConnection connection = null;             RandomAccessFile randomAccessFile = null;             InputStream is = null;             try {                             URL url = new URL(urlstr);                 connection = (HttpURLConnection) url.openConnection();                 connection.setConnectTimeout(5000);                 connection.setRequestMethod("GET");                 // 设置范围，格式为Range：bytes x-y;                 connection.setRequestProperty("Range", "bytes="+(startPos + compeleteSize) + "-" + endPos);                 randomAccessFile = new RandomAccessFile(localfile, "rwd");                 randomAccessFile.seek(startPos + compeleteSize);                 Log.i("RG", "connection--->>>"+connection);                 // 将要下载的文件写到保存在保存路径下的文件中                 is = connection.getInputStream();                 byte[] buffer = new byte[4096];                 int length = -1;                 while ((length = is.read(buffer)) != -1) {                     randomAccessFile.write(buffer, 0, length);                     compeleteSize += length;                     // 更新数据库中的下载信息                     dao.updataInfos(threadId, compeleteSize, urlstr);                     // 用消息将下载信息传给进度条，对进度条进行更新                     Message message = Message.obtain();                     message.what = 1;                     message.obj = urlstr;                     message.arg1 = length;                     mHandler.sendMessage(message);                     if (state == PAUSE) {                         return;                     }                 }             } catch (Exception e) {                 e.printStackTrace();             } finally {                 try {                     is.close();                     randomAccessFile.close();                     connection.disconnect();                     dao.closeDb();                 } catch (Exception e) {                     e.printStackTrace();                 }             }         }     }     //删除数据库中urlstr对应的下载器信息     public void delete(String urlstr) {         dao.delete(urlstr);     }     //设置暂停     public void pause() {         state = PAUSE;     }     //重置下载状态     public void reset() {        state = INIT;     } }

Dao:

package com.example.downloaderstopsart;import java.util.ArrayList;import java.util.List;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;public class Dao {private DBHelper dbHelper;public Dao(Context context) {dbHelper = new DBHelper(context);}/** * 查看数据库中是否有数据 */public boolean isHasInfors(String urlstr) {SQLiteDatabase database = dbHelper.getReadableDatabase();String sql = "select count(*)  from download_info where url=?";Cursor cursor = database.rawQuery(sql, new String[] { urlstr });cursor.moveToFirst();int count = cursor.getInt(0);cursor.close();return count == 0;}/** * 36 * 保存 下载的具体信息 37 */public void saveInfos(List<DownloadInfo> infos) {SQLiteDatabase database = dbHelper.getWritableDatabase();for (DownloadInfo info : infos) {String sql = "insert into download_info(thread_id,start_pos, end_pos,compelete_size,url) values (?,?,?,?,?)";Object[] bindArgs = { info.getThreadId(), info.getStartPos(),info.getEndPos(), info.getCompeleteSize(), info.getUrl() };database.execSQL(sql, bindArgs);}}/** * 得到下载具体信息 */public List<DownloadInfo> getInfos(String urlstr) {List<DownloadInfo> list = new ArrayList<DownloadInfo>();SQLiteDatabase database = dbHelper.getReadableDatabase();String sql = "select thread_id, start_pos, end_pos,compelete_size,url from download_info where url=?";Cursor cursor = database.rawQuery(sql, new String[] { urlstr });while (cursor.moveToNext()) {DownloadInfo info = new DownloadInfo(cursor.getInt(0),cursor.getInt(1), cursor.getInt(2), cursor.getInt(3),cursor.getString(4));list.add(info);}cursor.close();return list;}/** * 更新数据库中的下载信息 */public void updataInfos(int threadId, int compeleteSize, String urlstr) {SQLiteDatabase database = dbHelper.getReadableDatabase();String sql = "update download_info set compelete_size=? where thread_id=? and url=?";Object[] bindArgs = { compeleteSize, threadId, urlstr };database.execSQL(sql, bindArgs);}/** * 关闭数据库 */public void closeDb() {dbHelper.close();}/** * 下载完成后删除数据库中的数据 */public void delete(String url) {SQLiteDatabase database = dbHelper.getReadableDatabase();database.delete("download_info", "url=?", new String[] { url });database.close();}}

xml如下：

<?xml version="1.0" encoding="utf-8"?>  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"      android:orientation="vertical"      android:layout_width="fill_parent"      android:layout_height="fill_parent"      android:id="@+id/llRoot">      <ListView android:id="@android:id/list"          android:layout_width="fill_parent"          android:layout_height="fill_parent">     </ListView> </LinearLayout> 

item_list.xml：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="wrap_content"    android:orientation="vertical" >    <LinearLayout        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_marginBottom="5dip"        android:orientation="horizontal" >        <TextView            android:id="@+id/tv_resouce_name"            android:layout_width="fill_parent"            android:layout_height="wrap_content"            android:layout_weight="1" />        <Button            android:id="@+id/btn_start"            android:layout_width="fill_parent"            android:layout_height="wrap_content"            android:layout_weight="1"            android:onClick="startDownload"            android:text="下载" />        <Button            android:id="@+id/btn_pause"            android:layout_width="fill_parent"            android:layout_height="wrap_content"            android:layout_weight="1"            android:onClick="pauseDownload"            android:text="暂停" />    </LinearLayout></LinearLayout>

记得加权限：

<uses-permission android:name="android.permission.INTERNET"/>　<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

还有在3.0以上的版本记得加上这句话：

 StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectDiskReads().detectDiskWrites().detectNetwork().penaltyLog().build());        StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder().detectLeakedSqlLiteObjects().detectLeakedClosableObjects().penaltyLog().penaltyDeath().build());

效果图如下：