android网络编程之HttpUrlConnection的讲解--实现文件的断点上传

1、网络开发不要忘记在配置文件中添加访问网络的权限

<uses-permission android:name="android.permission.INTERNET"/>

2、网络请求、处理不能在主线程中进行，一定要在子线程中进行。因为网络请求一般有1~3秒左右的延时，在主线程中进行造成主线程的停顿，对用户体验来说是致命的。（主线程应该只进行ＵＩ绘制，像网络请求、资源下载、各种耗时操作都应该放到子线程中）。

3、Android端程序

public class MoreUploadActivity extends Activity {
    private TextView mTvMsg;

    private String result = "";

    private long start = 0;           // 开始读取的位置
    private long stop = 1024 * 1024;  // 结束读取的位置
    private int times = 0;            //读取次数

    private long fileSize = 0;  //文件大小

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_times_upload);

        initView();
    }

    private void initView(){
        mTvMsg = (TextView) findViewById(R.id.tv_upload);

        try {
            FileInputStream file = new FileInputStream(Environment.getExternalStorageDirectory().getPath() + "/aaaaa/baidu_map.apk");
            fileSize = file.available();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        new Thread(uploadThread).start();
    }

    private Thread uploadThread = new Thread(){
        public void run() {
            HttpURLConnection connection = null;
            try {
                URL url = new URL("http://192.168.23.1:8080/TestProject/MoreUploadTest");
                connection = (HttpURLConnection) url.openConnection();
                connection.setRequestMethod("POST");
                connection.setChunkedStreamingMode(51200);
                connection.setUseCaches(false);
                // 设置允许输出
                connection.setDoOutput(true);
                // 设置断点开始，结束位置
                connection.setRequestProperty("Range", "bytes=" + start + "-" + stop);

                String path = Environment.getExternalStorageDirectory().getPath() + "/aaaaa/baidu_map.apk";
                RandomAccessFile file = new RandomAccessFile(path, "rw");
                file.seek(start);
                byte[] buffer = new byte[1024];
                int count = 0;
                OutputStream os = connection.getOutputStream();
                if(fileSize > 1024*1024){
                    for(int i=0; i<1024 && count!=-1; i++){
                        count = file.read(buffer);
                        os.write(buffer, 0, count);
                    }
                }else{
                    for(int i=0; i<(fileSize/1024)+1 && count!=-1; i++){
                        count = file.read(buffer);
                        os.write(buffer, 0, count);
                    }
                }
                os.flush();
                os.close();

                Log.e("ABC", connection.getResponseCode() + "");
                if(connection.getResponseCode() == 200){
                    result += StringStreamUtil.inputStreamToString(connection.getInputStream()) + "\n";
                }

                start = stop + 1;
                stop += 1024*1024;
                fileSize -= 1024*1024;

                Message msg = Message.obtain();
                msg.what = 0;
                uploadHandler.sendMessage(msg);
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if(connection != null){
                    connection.disconnect();
                }
            }
        };
    };

    private Handler uploadHandler = new Handler(){
        public void handleMessage(android.os.Message msg) {
            if(msg.what == 0){
                if(times >= 8){
                    mTvMsg.setText(result);
                }else{
                    times += 1;
                    new Thread(uploadThread).start();
                    mTvMsg.setText(result);
                }
            }
        };
    };
}

4、服务器端使用Servlet开发，这里只给出doPost()方法

public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String range = request.getHeader("Range");
        int start = Integer.parseInt(range.substring(6, range.indexOf("-")));
        int stop = Integer.parseInt(range.substring(range.indexOf("-")+1, range.length()));

        RandomAccessFile file = new RandomAccessFile("F:/JavaWeb/TestProject/WebRoot/files/baidu.apk", "rw");
        file.seek(start);
        InputStream is = request.getInputStream();
        byte[] buffer = new byte[1024];
        int count = 0;
        while((count=is.read(buffer)) != -1){
            file.write(buffer, 0, count);
        }
        if(is != null){
            is.close();
        }
        if(file != null){
            file.close();
        }

        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");
        PrintWriter out = response.getWriter();
        out.println("文件上传成功" + start + "-" + stop);
        out.flush();
        out.close();
    }

5、最主要的就是一：设置断点setRequestProperty("Range", "bytes=0-1024")，获取断点request.getHeader("Range")

二：通过RandomAccessFile来读写文件

6、对于输出流的三个方法的对比：

os.write(byte[] buffer);   可能出现错误，因为你每次读取的数据小于等于1024，但你每次写入的数据仍然是1024， 对图片有一定影响，对安装包绝对是致命的影响。
    os.write(int oneByte);     效率低
    os.write(byte[] buffer, int byteOffset, int byteCount);   效率高，和第二个方法相比有一个数量级的差别（主观上看，有兴趣的可以测几下）。

7、参考博文：http://blog.sina.com.cn/s/blog_413580c20100wmr8.html