dart - How to upload images and file to a server in Flutter?

Question

I use a web service for image processing , it works well in Postman:

Now I want to make http request in flutter with Dart:

import 'package:http/http.dart' as http;

static ocr(File image) async {
    var url = '${API_URL}ocr';
    var bytes = image.readAsBytesSync();

    var response = await http.post(
        url,
        headers:{ "Content-Type":"multipart/form-data" } ,
        body: { "lang":"fas" , "image":bytes},
        encoding: Encoding.getByName("utf-8")
    );

    return response.body;

  }

but I don't know how to upload the image file, in above code I get exception: Bad state: Cannot set the body fields of a Request with content-type "multipart/form-data".
How should I write the body of request?

Answer 1

I'd like to recommend dio package to you , dio is a powerful Http client for Dart/Flutter, which supports Interceptors, FormData, Request Cancellation, File Downloading, Timeout etc.

dio is very easy to use, in this case you can:

Sending FormData:

FormData formData = new FormData.from({
   "name": "wendux",
   "file1": new UploadFileInfo(new File("./upload.jpg"), "upload1.jpg")
});
response = await dio.post("/info", data: formData)

More details please refer to dio。