android中的文件（图片）上传

android中的文件（图片）上传其实没什么复杂的，主要是对 multipart/form-data 协议要有所了解。

关于 multipart/form-data 协议，在 RFC文档中有详细的描述 RFC 2388 - Returning Values from Forms: multipart/form-data

大家有兴趣的话可以去看看，这里有一篇非常好的文章进行了介绍：Http协议中的数据传送之多重表单提交--multipart/form-data

那么在Android中如何实现呢？这里写了一个简单的工具类，供大家使用

UploadUtil

package com.atwal.util;

import android.util.Log;

import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.Map;
import java.util.UUID;

/**
 * Created by atwal on 2016/3/11.
 */
public class UploadUtil {
    private static final String TAG = "uploadFile";
    private static final int TIME_OUT = 10 * 1000;   //超时时间
    private static final String CHARSET = "utf-8";
    private static final String BOUNDARY = UUID.randomUUID().toString();  //边界标识随机生成
    private static final String PREFIX = "--";
    private static final String LINE_END = "\r\n";
    private static final String CONTENT_TYPE = "multipart/form-data";   //内容类型

    /**
     * 上传文件
     * @param file 文件
     * @param RequestURL post地址
     * @param params 除文件外其他参数
     * @param uploadFieldName 上传文件key
     * @return
     */
    public static String uploadFile(File file, String RequestURL, Map<String, String> params, String uploadFieldName) {
        String result = null;

        try {
            URL url = new URL(RequestURL);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(TIME_OUT);
            conn.setConnectTimeout(TIME_OUT);
            conn.setDoInput(true);
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Charset", CHARSET);
            conn.setRequestProperty("connection", "keep-alive");
            conn.setRequestProperty("Content-Type", CONTENT_TYPE + ";boundary=" + BOUNDARY);

            DataOutputStream dos = new DataOutputStream(conn.getOutputStream());
            StringBuffer sb = new StringBuffer();
            sb.append(getRequestData(params));

            if (file != null) {
                sb.append(PREFIX);
                sb.append(BOUNDARY);
                sb.append(LINE_END);
                sb.append("Content-Disposition: form-data; name=\"" + uploadFieldName + "\"; filename=\"" + file.getName() + "\"" + LINE_END);
                sb.append("Content-Type: application/octet-stream; charset=" + CHARSET + LINE_END);
                sb.append(LINE_END);
            }
            dos.write(sb.toString().getBytes());
            if (file != null) {
                InputStream is = new FileInputStream(file);
                byte[] bytes = new byte[1024];
                int len = 0;
                while ((len = is.read(bytes)) != -1) {
                    dos.write(bytes, 0, len);
                }
                is.close();
                dos.write(LINE_END.getBytes());
                byte[] end_data = (PREFIX + BOUNDARY + PREFIX + LINE_END).getBytes();
                dos.write(end_data);
            }
            dos.flush();

            int res = conn.getResponseCode();
            Log.e(TAG, "response code:" + res);
            if (res == 200) {
                Log.e(TAG, "request success");
                InputStream input = conn.getInputStream();
                StringBuffer sb1 = new StringBuffer();
                int ss;
                while ((ss = input.read()) != -1) {
                    sb1.append((char) ss);
                }
                result = sb1.toString();
                Log.i(TAG, "result : " + result);
            } else {
                Log.e(TAG, "request error");
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

    /**
     * 对post参数进行编码处理
     * @param params post参数
     * @return
     */
    private static StringBuffer getRequestData(Map<String, String> params) {
        StringBuffer stringBuffer = new StringBuffer();
        try {
            for (Map.Entry<String, String> entry : params.entrySet()) {
                stringBuffer.append(PREFIX);
                stringBuffer.append(BOUNDARY);
                stringBuffer.append(LINE_END);
                stringBuffer.append("Content-Disposition: form-data; name=\"" + entry.getKey() + "\"" + LINE_END);
                stringBuffer.append(LINE_END);
                stringBuffer.append(URLEncoder.encode(entry.getValue(), CHARSET));
                stringBuffer.append(LINE_END);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return stringBuffer;
    }
}

代码比较简单，就不细说了，主要就是把参数及文件按协议进行拼接。

注：本类代码参考了android上传文件到服务器 一文，做了优化修改

调用

调用代码比较简单，这里需要注意的是，文件上传是一个网络操作，要另开线程处理。另外要给应用网络和SD卡读写权限。

String requestURL = "服务器地址";
String picPath = "图片地址";
File file = new File(picPath);
Log.i("upload", "file exists:" + file.exists());
if (file.exists()) {
    Map<String, String> params = new HashMap<>();
    params.put("id", "1");
    //...如果有其他参数添加到这里
    String request = UploadUtil.uploadFile(file, requestURL, params, "image");
    Log.i("upload", request);
}

当然，此工具类对异常信息并未处理，大家可根据自己的情况进行优化。