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 downloaders = new HashMap();// 存放与下载器对应的进度条private Map ProgressBars = new HashMap();/*** 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);}}}}};@Overridepublic 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> data = new ArrayList>();Map map = new HashMap();map.put("name", "mm.mp3");data.add(map);map = new HashMap();map.put("name", "pp.mp3");data.add(map);map = new HashMap();map.put("name", "tt.mp3");data.add(map);map = new HashMap();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 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();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;}@Overridepublic 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 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 getInfos(String urlstr) {List list = new ArrayList();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：

item_list.xml：

记得加权限：

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：