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