多线程下载断点续传

1.首先配置GreenDao网上好多博客，参照就好了

2.配置网络权限及其他依赖

3.布局

4.GreenDao的bean实体类

@Entity
public class Bean {
    @Id(autoincrement = true)
    long id;
    String downpath;
    int threadid;
    int downlength;
    public int getDownlength() {
        return this.downlength;
    }
    public void setDownlength(int downlength) {
        this.downlength = downlength;
    }
    public int getThreadid() {
        return this.threadid;
    }
    public void setThreadid(int threadid) {
        this.threadid = threadid;
    }
    public String getDownpath() {
        return this.downpath;
    }
    public void setDownpath(String downpath) {
        this.downpath = downpath;
    }
    public long getId() {
        return this.id;
    }
    public void setId(long id) {
        this.id = id;
    }
    @Generated(hash = 635468303)
    public Bean(long id, String downpath, int threadid, int downlength) {
        this.id = id;
        this.downpath = downpath;
        this.threadid = threadid;
        this.downlength = downlength;
    }
    @Generated(hash = 80546095)
    public Bean() {
    }
}

5.MainActivity

public class MainActivity extends AppCompatActivity {
    private FileDownloader loader;
    //声明控件
    @InjectView(R.id.btn)
    Button btn;
    @InjectView(R.id.pro)
    ProgressBar progressBar;
    @InjectView(R.id.tv)
    TextView tv;

    /**
     * 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:
                    long size = msg.getData().getInt("size");
                    long fileSize = loader.getFileSize();
                    float v = size  * 100 / fileSize;
                    progressBar.setProgress((int) size);
                    tv.setText(v+"%");
                    if(progressBar.getProgress()==progressBar.getMax()){
                        Toast.makeText(MainActivity.this, R.string.success, Toast.LENGTH_SHORT).show();
                    }
                    break;
                case -1:
                    Toast.makeText(MainActivity.this, R.string.error, Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化
        ButterKnife.inject(this);
        //切换文字
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(btn.getText().toString().equals("下载")){
                    btn.setText("暂停");


                }else{
                    btn.setText("下载");
                }

                // TODO Auto-generated method stub
                String path = "http://mirror.aarnet.edu.au/pub/TED-talks/911Mothers_2010W-480p.mp4";
                System.out.println(Environment.getExternalStorageState()+"------"+Environment.MEDIA_MOUNTED);

                if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
                    download(path, Environment.getExternalStorageDirectory());
                    Log.i("xx",Environment.getExternalStorageDirectory()+"");
                }else{
                    Toast.makeText(MainActivity.this, R.string.sdcarderror, Toast.LENGTH_SHORT).show();
                }
            }

            /**
             * 主线程(UI线程)
             * 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
             * @param path
             * @param savedir
             */
            private void download(final String path, final File savedir) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        loader = new FileDownloader(MainActivity.this, path, savedir, 3);
                        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();
            }
        });
    }}

6.DBOpenHelper

public class DBOpenHelper extends SQLiteOpenHelper {
    private static final String DBNAME = "down.db";
    private static final int VERSION = 1;

    public DBOpenHelper(Context context) {
        super(context, DBNAME, null, VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE IF NOT EXISTS filedownlog (id integer primary key autoincrement, downpath varchar(100), threadid INTEGER, downlength INTEGER)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS filedownlog");
        onCreate(db);
    }
}

7. FileDownloader

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 data = new ConcurrentHashMap();

    /* 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 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 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
     *
     * @param conn
     * @return
     */
    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 getHttpResponseHeader(HttpURLConnection http) {
        Map header = new LinkedHashMap();

        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 header = getHttpResponseHeader(http);

        for (Map.Entry entry : header.entrySet()) {
            String key = entry.getKey() != null ? entry.getKey() + ":" : "";
            print(key + entry.getValue());
        }
    }

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

8.FileService

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 getData(String path){
        SQLiteDatabase db = openHelper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select threadid, downlength from filedownlog where downpath=?", new String[]{path});
        Map data = new HashMap();

        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 map){//int threadid, int position
        SQLiteDatabase db = openHelper.getWritableDatabase();
        db.beginTransaction();

        try{
            for(Map.Entry entry : map.entrySet()){
                db.execSQL("insert into filedownlog(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 map){
        SQLiteDatabase db = openHelper.getWritableDatabase();
        db.beginTransaction();

        try{
            for(Map.Entry entry : map.entrySet()){
                db.execSQL("update filedownlog 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 filedownlog where downpath=?", new Object[]{path});
        db.close();
    }
}

9.DownThread

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;
    }
}

10.DownloadProgressListener

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