Okhttp post 上传图片文件

public class UploadHelper extends Presenter {

    public static final String TAG = "UploadHelper";
    private static final MediaType MEDIA_TYPE_PNG = MediaType.parse("image/png");
    private final OkHttpClient client = new OkHttpClient();

    public String upload(String imageType,String userPhone,File file) throws NetworkException{

        RequestBody fileBody = RequestBody.create(MediaType.parse("image/png"), file);

        RequestBody requestBody = new MultipartBody.Builder()
                .setType(MultipartBody.FORM)
///                .addPart(
//                        Headers.of("Content-Disposition", "form-data; name=\"file\"; filename=\"" + fileName + "\""),
//                        RequestBody.create(MEDIA_TYPE_PNG, file))
//                .addPart(
//                        Headers.of("Content-Disposition", "form-data; name=\"imagetype\""),
//                        RequestBody.create(null, imageType))
//                .addPart(
//                        Headers.of("Content-Disposition", "form-data; name=\"userphone\""),
//                        RequestBody.create(null, userPhone))

                .addFormDataPart("file", "head_image", fileBody)
                .addFormDataPart("imagetype", imageType)
                .addFormDataPart("userphone", userPhone)
                .build();

        Request request = new Request.Builder()
                .url("http://xxxxx")
                .post(requestBody)
                .build();

        Response response;
        try {
            response = client.newCall(request).execute();
            String jsonString = response.body().string();
            Log.d(TAG," upload jsonString ="+jsonString);

            if(!response.isSuccessful()){
                throw new NetworkException("upload error code "+response);
            }else{
                JSONObject jsonObject = new JSONObject(jsonString);
                int errorCode = jsonObject.getInt("errorCode");
                if(errorCode == 0){
                    Log.d(TAG," upload data ="+jsonObject.getString("data"));
                    return jsonObject.getString("data");
                }else {
                    throw new NetworkException("upload error code "+errorCode+",errorInfo="+jsonObject.getString("errorInfo"));
                }
            }

        } catch (IOException e) {
            Log.d(TAG,"upload IOException ",e);
        }catch (JSONException e){
            Log.d(TAG,"upload JSONException ",e);
        }
        return null;
    }

addPart 就是发送头部的具体内容了，其中 addFormDataPart 封装了部分内容，本质上 和

.addPart( 
Headers.of(“Content-Disposition”, “form-data; name=\”token\”“), 
RequestBody.create(null, uploadToken))