retrofit2上传文件

@Multipart
@POST("upload")
Call<ResponseBody> uploadFile(@Part MultipartBody.Part file);

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://api.example.com/")
    .build();

FileUploadService service = retrofit.create(FileUploadService.class);

File file = new File("path/to/file");
RequestBody requestBody = RequestBody.create(MediaType.parse("multipart/form-data"), file);

MultipartBody.Part filePart = MultipartBody.Part.createFormData("file", file.getName(), requestBody);

Call<ResponseBody> call = service.uploadFile(filePart);

call.enqueue(new Callback<ResponseBody>() {
    @Override
    public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
        if (response.isSuccessful()) {
            // 文件上传成功
        } else {
            // 文件上传失败
        }
    }

    @Override
    public void onFailure(Call<ResponseBody> call, Throwable t) {
        // 网络请求失败
    }
});