Android 断点续传进阶之多线程下载

今天继续下载的风骚走位内容---多线程多文件断点续传

Android 断点续传基础之单线程下载：http://blog.csdn.net/qq_27489007/article/details/53897653

效果图：

文件关系：

所需内容
多文件下载列表的显示
启动多个线程分段下载
使用通知栏显示进度条
使用其他方式实现线程通信

与单线程不主要不同：

任务下载类（DuoDownloadTask） 使用了线程池， 数据库对线程的增、删操作使用synchronized

多线程下载原理简介
假设要分3个线程下载一个100字节的文件，每个线程可以平分线程1(0-32字节)、 线程2(33-65字节)、线程3(66-100字节)

部分主要代码：

package com.example.test.service;import android.content.Context;import android.content.Intent;import com.example.test.DownloadDB.ThreadDAOImpl;import com.example.test.info.FileInfo;import com.example.test.info.TheardInfo;import java.io.File;import java.io.IOException;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import java.util.ArrayList;import java.util.List;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * 多线程多文件的下载任务类，为了学习查看方便 所以提出来了 * Created by lung on 2016-12-17. */public class DuoDownloadTask {    private Context mContext = null;    private FileInfo mFileInfo = null;    private ThreadDAOImpl mThreadDAO = null;    private long mFinished = 0;   //总的完成进度    public boolean isPause = false;   //暂停下载的开关    private int mThreadCount = 1;  //线程数量    private List<DownloadThread> downloadThreadList = null;//线程集合  方便管理    public static ExecutorService executorService = Executors.newCachedThreadPool();//线程池    public DuoDownloadTask(Context mContext, FileInfo mFileInfo, int mThreadCount) {        this.mContext = mContext;        this.mFileInfo = mFileInfo;        this.mThreadCount = mThreadCount;        mThreadDAO = new ThreadDAOImpl(mContext);    }    //下载的方法    public void download() {        //读取数据库的线程信息        List<TheardInfo> threaddInfos = mThreadDAO.getThreads(mFileInfo.getUrl());        if (threaddInfos.size() == 0) {  //如果数据库无线程信息            //获得每个线程下载的长度            int length = mFileInfo.getLength() / mThreadCount;            for (int i = 0; i < mThreadCount; i++) {                //  参数三线程开始的地方  参数四  线程结束的地方   参数五任务完成的进度                TheardInfo theardInfo = new TheardInfo(i, mFileInfo.getUrl(), length * i, (i + 1) * length - 1, 0);                //最后一个线程 会出现除不尽的情况                if (i == mThreadCount - 1) {                    //直接把线程的结束位置 设置成文件的最大长度位置                    theardInfo.setEnd(mFileInfo.getLength());                }                //添加到线程信息集合中                threaddInfos.add(theardInfo);                //向数据库插入线程信息                mThreadDAO.insertThread(theardInfo);            }        }        downloadThreadList = new ArrayList<>();        //启动多个线程进行下载        for (TheardInfo info : threaddInfos) {            DownloadThread thread = new DownloadThread(info);//            thread.start();  //开始线程添加到集合中            DuoDownloadTask.executorService.execute(thread);  //利用线程池来执行线程任务            downloadThreadList.add(thread);  //把线程添加进去方便ckeckAllThreadFinshed检查线程        }    }    //这个方法 用来判断所有的线程是否都执行完了    private synchronized void checkAllThreadFinshed() {        boolean allFinished = true;        //遍历线程集合，判断线程是否都执行完毕        for (DownloadThread thread : downloadThreadList) {            if (!thread.isFinished) {                allFinished = false;                break;            }        }        if (allFinished) {   //如果线程都完成了            //下载完成后  删除线程信息            //删除下载记录            mThreadDAO.deleteThread(mFileInfo.getUrl(), mFileInfo.getId());            //发送广播通知ui下载任务结束            Intent intent = new Intent(DuoDownloadService.ACTION_FINISHED);            intent.putExtra("fileInfo", mFileInfo);            mContext.sendBroadcast(intent);   //发送广播        }    }    class DownloadThread extends Thread {        private TheardInfo threadInfo;        public boolean isFinished = false; //用来标识线程是否结束        public DownloadThread(TheardInfo threadInfo) {            this.threadInfo = threadInfo;        }        @Override        public void run() {            //设置下载位置            try {                URL url = new URL(threadInfo.getUrl());                HttpURLConnection conn = (HttpURLConnection) url.openConnection();                conn.setRequestMethod("GET");                conn.setConnectTimeout(3000);                //开始的字节数 为开始加上完成的长度                long start = threadInfo.getStart() + threadInfo.getFinished();                //下载的范围  开始的字节数 到结束的字节数                conn.setRequestProperty("Range", "bytes=" + start + "-" + threadInfo.getEnd());                //设置文件写入位置   路径 文件名                File file = new File(DownloadService.DOWNLOAD_PATH, mFileInfo.getFileName());                //                RandomAccessFile raf = new RandomAccessFile(file, "rwd");                raf.seek(start);  //文件的写入位置                Intent intent = new Intent(DownloadService.ACTION_UPDATE);//把进度广播发送给activity 所以需要intent                mFinished += threadInfo.getFinished();//从线程中拿到完成的进度                //开始下载                if (conn.getResponseCode() == 206) {                    //读取数据                    InputStream input = conn.getInputStream();                    byte[] buffer = new byte[1024 * 4];                    int len = -1;                    long time = System.currentTimeMillis();  //拿到当前时间                    while ((len = input.read(buffer)) != -1) {                        //写入文件                        raf.write(buffer, 0, len);                        //把下载进度发送广播给activity                        mFinished += len; //把现在下载的进度累加进去                        //累加每个线程完成的进度                        threadInfo.setFinished(threadInfo.getFinished() + len);                        if (System.currentTimeMillis() - time > 1000) {   //减少ni负载 大于10秒发送更新                            time = System.currentTimeMillis();                            //以百分比的形式发送给广播                            intent.putExtra("finished", (int) (mFinished * 100 / mFileInfo.getLength()));                            intent.putExtra("id", mFileInfo.getId());                            mContext.sendBroadcast(intent);                        }                        //在下载暂停时，保存下载进度                        if (isPause) {     //如果暂停   把线程信息进行保存   最后一个参数  他会把每个线程的 进度保存起来                            mThreadDAO.updateThread(mFileInfo.getUrl(), mFileInfo.getId(), threadInfo.getFinished());                            return;                        }                    }                    intent.putExtra("finished", 100);                    mContext.sendBroadcast(intent);  //发送广播                    // 标识线程执行完毕                    isFinished = true;                    //每个线程执行完毕 都执行去判断 所有的线程是否都执行完毕                    checkAllThreadFinshed();                    input.close();                }                raf.close();                conn.disconnect();            } catch (MalformedURLException e) {                e.printStackTrace();            } catch (IOException e) {                e.printStackTrace();            } finally {   //关闭各种链接            }            super.run();        }    }}

ThreadDAOImpl.java

package com.example.test.DownloadDB;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import com.example.test.info.TheardInfo;import java.util.ArrayList;import java.util.List;/** * 数据访问接口实现类 * Created by lung on 2016-12-07. */public class ThreadDAOImpl implements ThreadDAO {    private DBHelper mHelper=null;    public ThreadDAOImpl(Context context){        mHelper=DBHelper.getInstance(context);    }    //插入线程信息    @Override    public synchronized void insertThread(TheardInfo threadInfo) {   //加锁进行同步        SQLiteDatabase db=mHelper.getWritableDatabase();//获得可写的数据库        db.execSQL("insert into thread_info(thread_id,url,start,end,finished) values(?,?,?,?,?)",new Object[]{threadInfo.getId(), threadInfo.getUrl(),                threadInfo.getStart(), threadInfo.getEnd(), threadInfo.getFinished()});        db.close();    }    //删除线程    @Override    public synchronized void deleteThread(String url, int thread_id) {        SQLiteDatabase db=mHelper.getWritableDatabase();//获得可写的数据库        db.execSQL("delete from  thread_info where url = ? and thread_id=?",                new Object[]{url, thread_id});        db.close();    }   //更新线程下载进度    @Override    public synchronized void updateThread(String url, int thread_id, long finished) {        SQLiteDatabase db=mHelper.getWritableDatabase();//获得可写的数据库        db.execSQL("update thread_info set finished = ?  where url = ? and thread_id=?",                new Object[]{finished, url, thread_id});        db.close();    }    //查询文件的线程信息    @Override    public List<TheardInfo> getThreads(String url) {        List<TheardInfo> list = new ArrayList<>();        SQLiteDatabase db = mHelper.getWritableDatabase();        Cursor cursor = db.rawQuery("select * from thread_info where url=?", new String[]{url});        while (cursor.moveToNext()) {            TheardInfo thread = new TheardInfo();            thread.setId(cursor.getInt(cursor.getColumnIndex("thread_id")));            thread.setUrl(cursor.getString(cursor.getColumnIndex("url")));            thread.setStart(cursor.getInt(cursor.getColumnIndex("start")));            thread.setEnd(cursor.getInt(cursor.getColumnIndex("end")));            thread.setFinished(cursor.getInt(cursor.getColumnIndex("finished")));            list.add(thread);        }        cursor.close();        db.close();        return list;    }    @Override    public boolean isExists(String url, int thread_id) {        SQLiteDatabase db = mHelper.getReadableDatabase();        Cursor cursor = db.rawQuery("select * from thread_info where url=? and thread_id = ?",                new String[]{url, String.valueOf(thread_id)});        boolean isExist = cursor.moveToNext();        cursor.close();        db.close();        return isExist;    }}

附上Demo：http://download.csdn.net/detail/qq_27489007/9722868