android_uploader/lib/file_request.dart

import 'dart:async';

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

typedef OnProgress = void Function(int bytes, int totalBytes);

class FileRequest extends http.MultipartRequest {
  FileRequest(
    super.method,
    super.url,
    this.onProgress,
  );

  final OnProgress onProgress;

  @override
  http.ByteStream finalize() {
    final byteStream = super.finalize();

    final total = contentLength;
    int bytes = 0;

    final t = StreamTransformer.fromHandlers(
      handleData: (List<int> data, EventSink<List<int>> sink) {
        bytes += data.length;
        onProgress(bytes, total);
        if (total >= bytes) {
          sink.add(data);
        }
      },
    );
    final stream = byteStream.transform(t);
    return http.ByteStream(stream);
  }
}