android下载断点续传

来源：互联网发布：tensorflow训练mnist 编辑：程序博客网时间：2024/06/16 10:25

先贴图开始下载

这里写图片描述
暂停下载

杀进程或关闭activity后，再次启动可正常下载，不会做动态图，这里就不贴图了

下载完成后，红框标记即为下载后文件
这里写图片描述
MainActivit里onCreate()里代码如下，主要做一些变量和UI的初始化工具：

public void onCreate(Bundle icicle) {        super.onCreate(icicle);        setContentView(R.layout.activity_main);        pbBar = (ProgressBar) findViewById(R.id.progressBar);        tv = (TextView) findViewById(R.id.textView);        bt_start= (Button) findViewById(R.id.button);        // 启动时对文件做处理        File file = new File(filePath);        //查询数据库，更新UI        dao = new DownInfoDao(this);        DownInfo info = dao.query(path);        Log.i("guoguo", info+"=info");        if (info == null) {            isFinished=false;            if (file.exists()) {                file.delete();                Log.i("guoguo", "删除文件");            }        } else {            fileSize=info.getTotal();            downlen = info.getDownLen();            if (fileSize>0) {                progress = (int)(((float)downlen /(float) fileSize)* 100) ;                if (downlen==fileSize) {                    isFinished=true;                }            }            if (!file.exists()) {                dao.delete(path);            }            pbBar.setProgress(progress);            tv.setText(progress + "%");        }        //启动服务        Intent it = new Intent(this, DownloadService.class);        bindService(it, conn, Context.BIND_AUTO_CREATE);        startService(it);    }1
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更新回调及handler:

private ICallbackResult callback = new ICallbackResult() {        @Override        public void OnBackResult(int total, int downlen) {            // TODO Auto-generated method stub            //接收回调数据            Log.i("guoguo", "downlen="+downlen+",total="+total);                int pro =  (int)(((float)downlen /(float) total)* 100)  ;                Message msg = new Message();                msg.what = 1;                msg.obj = pro;                handler.sendMessage(msg);        }    };    //更新UI     Handler handler=new Handler(){        public void handleMessage(Message msg) {            switch (msg.what) {            case 1:                int progress=(Integer) msg.obj;                pbBar.setProgress(progress);                if (progress==100) {                    isFinished=true;                }                tv.setText(progress+"%");                break;            default:                break;            }        };    };1
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核心代码来了，主要工作在service里完成，以下是文件的下载部分，：

try {                URL url = new URL(path);                HttpURLConnection conn = (HttpURLConnection) url                        .openConnection();                DownInfo info = dao.query(path);                //若查询不到数据，刚建立 一个DownInfo对象                if (info==null) {                    info=new DownInfo(path, 0, fileSize);                    dao.insert(info);                }else {                    //数据库里存在，更新下载位置                    downlen=info.getDownLen();                    fileSize=info.getTotal();                    //设置从downlen位置开始读取                    conn.setRequestProperty("Range", "bytes=" + downlen + "-" + fileSize);                 }                conn.connect();                int length = conn.getContentLength();                if (fileSize==0) {                    fileSize=length;                }                InputStream is = conn.getInputStream();                File file = new File(savePath);                if (!file.exists()) {                    file.mkdirs();                }                RandomAccessFile apkFile = new RandomAccessFile(saveFileName,"rwd");                apkFile.seek(downlen);  //文件定位到文件末尾                //设置缓存                byte buf[] = new byte[1024*1024];                //开始下载文件                do {                    //对dao做处理，来实现暂停功能                    while (isPause) {                        synchronized (dao) {                            try {                                dao.wait();                            } catch (InterruptedException e) {                                e.printStackTrace();                            }                        }                      }                    //读取流                    int numread = is.read(buf);                    //写入文件                    if (numread > 0) {                        downlen += numread;                        apkFile.write(buf, 0, numread);                    }else {                        //下载完成                        Message msg = mHandler.obtainMessage();                        msg.what = 1;                        mHandler.sendEmptyMessage(0);                        canceled = true;                        break;                    }                } while (!canceled);//                 apkFile.close();                is.close();            } catch (MalformedURLException e) {                e.printStackTrace();            } catch (IOException e) {                e.printStackTrace();            }1
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现在为文件的更新部分

                //发起网络请求                url = new URL(path);                URLConnection conn = url.openConnection();                fileSize = conn.getContentLength();                if (downLoadThread == null || !downLoadThread.isAlive()) {                    downLoadThread = new Thread(mdownApkRunnable);                    downLoadThread.start();                }                DownInfo info = dao.query(path);                if (info != null) {                        downlen = info.getDownLen();//                      if (fileSize==-1) {                            fileSize=info.getTotal();//                      }                }                while (!flag) {                    while (isPause) {                        synchronized (dao) {                            try {                                dao.wait();                            } catch (InterruptedException e) {                                e.printStackTrace();                            }                        }                      }                    //下载完成或暂停时，停止 更新                    if (downlen==fileSize||isPause) {                        flag=true;                    }                    //存入数据库                    dao.update(new DownInfo(path, downlen,fileSize));                    //更新UI                    callback.OnBackResult(fileSize,downlen);                    //设置为0.2秒更新一次                    Thread.sleep(200);                }1
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下载和更新工作如果在同一个线程里处理里下载速度会非常慢，所以我把两个工作分开来处理，这样能保证下载速度。

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