//-----------UploadThread ---------------
public class UploadThread extends Thread {
	private String fileName;

	private String url;
public UploadThread(String fileName,String url) {
	// TODO Auto-generated constructor stub
	this.url=url;
	this.fileName=fileName;
}

	@Override
	public void run() {
		
		String boundary = "---------------------------7e130613d0e3a";
		String prefix = "--";
		String end = "\r\n";

		try {
			URL HttpUrl = new URL(url);
			HttpURLConnection connection = (HttpURLConnection) HttpUrl
					.openConnection();
			connection.setRequestMethod("POST");
			connection.setDoOutput(true);
			connection.setDoInput(true);
			
			connection.setRequestProperty("Content-Type","multipart/form-data;boundary="+ boundary); // 通过 multipart
				DataOutputStream out=new DataOutputStream(connection.getOutputStream())	;											// 协议向服务器发送数据
                out.writeBytes(prefix+boundary+end);
                out.writeBytes("Content-Description:form-data;"+"name=\"file\";filename=\""+"Sky.jpg"+"\""+end);
		
                out.writeBytes(end);
                FileInputStream fileInputStream=new FileInputStream(new File(fileName));
		byte[]b=new byte[1024*4]; 
		int len;
		while((len=fileInputStream.read(b))!=-1){
			out.write(b,0,len);
		
		}
		out.writeBytes(end);
		out.writeBytes(prefix+boundary+prefix+end);
		out.flush();
		BufferedReader reader=new BufferedReader(new InputStreamReader(connection.getInputStream()));
		StringBuffer sbBuffer=new StringBuffer();
		String str;
		while((str=reader.readLine())!=null){
			
			sbBuffer.append(str);
			
			
		}
		System.out.println("------respose:"+sbBuffer.toString());
		if (out!=null) {
			out.close();
		}
		if (reader!=null) {
			reader.close();
		}
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

}


//----------------UploadActivity-----------------------
public class UploadActivity extends Activity {
	private Button button;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.upload);
		button = (Button) findViewById(R.id.button1);
		button.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				String url = "http://172.16.166.195:8080/Upload/";
				File file = Environment.getExternalStorageDirectory();
				File fileAbs = new File(file, "sky.jpg");
				String fileName = fileAbs.getAbsolutePath();
				UploadThread thread = new UploadThread(fileName, url);
				thread.start();
			}
		});

	}
}

ps:权限都加了的