Android断点续传学习

先学习断点续传热热身，为多线程下载预热；

其实重点就是下载这里；

1，下载范围的设定

 urlConnection.setRequestProperty("Range","bytes=" + start + "-" + info.getLength());  

2 , 文件移动到指定位置

randomFile.seek(start); 

其他的没有难度，很简单；可以使用数据库或者文件作为缓存文件

主要是一个思路；这里简单的记录一下；作为学习记录

1.    class MyThread extends Thread{  
2.         private FileInfo info = null;  
3.         public MyThread(FileInfo threadInfo) {  
4.             this.info = threadInfo;  
5.         }  
6.         @Override  
7.         public void run() {  
8.             //向数据库添加线程信息  
9.             if(!threadDAO.isExits(info.getUrl())){  
10.                 threadDAO.insert(info);  
11.             }  
12.             HttpURLConnection urlConnection = null;  
13.             RandomAccessFile randomFile =null;  
14.             InputStream inputStream = null;  
15.             try {  
16.                 URL url = new URL(info.getUrl());  
17.                 urlConnection = (HttpURLConnection) url.openConnection();  
18.                 urlConnection.setConnectTimeout(3000);  
19.                 urlConnection.setRequestMethod("GET");  
20.                 //设置下载位置  
21.                 int start = info.getStart() + info.getNow();  
22.                 urlConnection.setRequestProperty("Range","bytes=" + start + "-" + info.getLength());  
23.   
24.                 //设置文件写入位置  
25.                 File file = new File(DOWNLOAD_PATH,FILE_NAME);  
26.                 randomFile = new RandomAccessFile(file, "rwd");  
27.                 randomFile.seek(start);  
28.   
29.                 //向Activity发广播  
30.                 Intent intent = new Intent(ACTION_UPDATE);  
31.                 finished += info.getNow();  
32.   
33.                 if (urlConnection.getResponseCode() == HttpStatus.SC_PARTIAL_CONTENT) {  
34.                     //获得文件流  
35.                     inputStream = urlConnection.getInputStream();  
36.                     byte[] buffer = new byte[512];  
37.                     int len = -1;  
38.                     long time = System.currentTimeMillis();  
39.                     while ((len = inputStream.read(buffer))!= -1){  
40.                         //写入文件  
41.                         randomFile.write(buffer,0,len);  
42.                         //把进度发送给Activity  
43.                         finished += len;  
44.                         //看时间间隔，时间间隔大于500ms再发  
45.                         if(System.currentTimeMillis() - time >500){  
46.                             time = System.currentTimeMillis();  
47.                             intent.putExtra("now",finished *100 /fileInfo.getLength());  
48.                             context.sendBroadcast(intent);  
49.                         }  
50.                         //判断是否是暂停状态  
51.                         if(isPause){  
52.                             threadDAO.update(info.getUrl(),finished);  
53.                             return; //结束循环  
54.                         }  
55.                     }  
56.                     //删除线程信息  
57.                     threadDAO.delete(info.getUrl());  
58.                 }  
59.             }catch (Exception e){  
60.                 e.printStackTrace();  
61.             }finally {//回收工作略  
62.             }  
63.         }  
64.     }  
65. }