介面類

    @Multipart
    @POST("file/upload")
    Call<Result<String>> upheader(@Part List<MultipartBody.Part> partList);

Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://www.zhaoapi.cn/")

//新增證書的方法  可以不用寫
                .client(setCard())
                .addConverterFactory(GsonConverterFactory.create())
                .build(); 	
 File file = new File("/mnt/sdcard/img.jpg");
  MultipartBody.Builder builder = new MultipartBody.Builder().addFormDataPart("uid", "100");
        //for迴圈上傳多個檔案
        RequestBody requestBody = RequestBody.create(MediaType.parse("multipart/form-data"), file);
        builder.addFormDataPart("file", file.getName(), requestBody);//]
        //給檔案list新增資料
        List<MultipartBody.Part> parts = builder.build().parts();

        Upload upload = retrofit.create(Upload.class);
        Call<Result<String>> upheader = upload.upheader(parts);
        upheader.enqueue(new Callback<Result<String>>() {
            @Override
            public void onResponse(Call<Result<String>> call, Response<Result<String>> response) {
                Toast.makeText(MainActivity.this, "上傳成功", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onFailure(Call<Result<String>> call, Throwable t) {

            }
        });