之所以想记录下来，主要是之前对这个不太熟，然后在网上找了大半天也没找到合适的，然后自己慢慢试了出来，比较囧。。。但分享给大家，亲测可用！

主要分为两步：
1. 将图片url转为二进制字符串；
2. 将二进制字符串以及其他字段一并上传。

直接上代码：

public class HttpClient {

    public static final OkHttpClient client =
            new OkHttpClient.Builder()
                    .connectTimeout(10, TimeUnit.SECONDS)
                    .readTimeout(10, TimeUnit.SECONDS)
                    .build();

    public static String getResponse(String url, String imgUrl) throws IOException {

        RequestBody fileBody = RequestBody.create(MediaType.parse("image/jpeg"), getFile(imgUrl));

        RequestBody requestBody = new MultipartBody.Builder()
                .setType(MultipartBody.FORM)
                .addFormDataPart("param1", param1)
                .addFormDataPart("param2", param2)
                .addFormDataPart("image", "image", fileBody)
                .build();

        Request request = new Request.Builder()
                .url(url)
                .post(requestBody)
                .build();
        Response response = client.newCall(request).execute();
        if (response.isSuccessful()) {

            return response.body().string();
        } else {

            throw new RuntimeException(response.body().string());
        }
    }

    private static byte[] getFile(String imgUrl) throws IOException {

        Request request = new Request.Builder()
                .url(imgUrl)
                .build();
        Response response = client.newCall(request).execute();
        if (response.isSuccessful()) {
            return response.body().bytes();
        } else {
            throw new RuntimeException(response);
        }
    }
}

其中OkHttpClient包请自行导入。