Upload image in flutter web

Question

Flutter web is still in technical preview but i want to pick an image from the disk and upload it to the server. Is there anyway to add HTML, JS to my flutter web project a

Answer 1

You can use image_picker_web :

dependencies:
  image_picker_web: ^1.0.9

picks Images (as Widget, File or Uint8List) and Videos (as File or Uint8List)

Answer 2

You need addEventListener and also need to append it for woking it on mobile safari. I answered here too.

Future<void> _setImage() async {
    final completer = Completer<List<String>>();
    InputElement uploadInput = FileUploadInputElement();
    uploadInput.multiple = true;
    uploadInput.accept = 'image/*';
    uploadInput.click();
    // onChange doesn't work on mobile safari
    uploadInput.addEventListener('change', (e) async {
        // read file content as dataURL
        final files = uploadInput.files;
        Iterable<Future<String>> resultsFutures = files.map((file) {
            final reader = FileReader();
            reader.readAsDataUrl(file);
            reader.onError.listen((error) => completer.completeError(error));
            return reader.onLoad.first.then((_) => reader.result as String);
        });

        final results = await Future.wait(resultsFutures);
        completer.complete(results);
    });
    // need to append on mobile safari
    document.body.append(uploadInput);
    final List<String> images = await completer.future;
    setState(() {
        _uploadedImages = images;
    });
    uploadInput.remove();
}

This also works:

Future<void> _setImage() async {   
    final completer = Completer<List<String>>();
    final InputElement input = document.createElement('input');
    input
      ..type = 'file'
      ..multiple = true
      ..accept = 'image/*';
    input.click();
    // onChange doesn't work on mobile safari
    input.addEventListener('change', (e) async {
      final List<File> files = input.files;
      Iterable<Future<String>> resultsFutures = files.map((file) {
        final reader = FileReader();
        reader.readAsDataUrl(file);
        reader.onError.listen((error) => completer.completeError(error));
        return reader.onLoad.first.then((_) => reader.result as String);
      });
      final results = await Future.wait(resultsFutures);
      completer.complete(results);
    });
    // need to append on mobile safari
    document.body.append(input);
    // input.click(); can be here
    final List<String> images = await completer.future;
    setState(() {
      _uploadedImages = images;
    });
    input.remove();
}

Answer 3

This will do what you want for web. Just call it from any button and it will open the system dialog to chose the file.

import 'dart:typed_data';
import 'package:universal_html/prefer_sdk/html.dart';    
import '../../../providers/form_provider.dart';

Uint8List uploadedImage;

startFilePickerWeb(ProviderForm formProvider) async {    
  InputElement uploadInput = FileUploadInputElement();
  uploadInput.click();

  uploadInput.onChange.listen((e) {
    // read file content as dataURL
    final files = uploadInput.files;
    if (files.length == 1) {
      final file = files[0];
      FileReader reader = FileReader();

      reader.onLoadEnd.listen((e) {
      //Here I send the imatge to my Provider 
        formProvider.setLogoEmpresa(reader.result);
      });

      reader.onError.listen((fileEvent) {
        print("Some Error occured while reading the file");
      });

      reader.readAsArrayBuffer(file);
    }
  });
}

The provider:

class ProviderForm extends ChangeNotifier {
    Uint8List logoEmpresa;
    void setLogoEmpresa(Uint8List newFile) {
       logoEmpresa = newFile;
       notifyListeners();
    }
}

Then in your view you can render it like this, in case no imatge it show a attachement icon:

Container(
      width: formProvider.logoEmpresa == null
          ? 70.0
          : 90.0,
      child: formProvider.logoEmpresa == null
          ? Icon(
              Icons.attach_file,
              size: 70.0,
              color: kColorPrincipal,
            )
          : Image.memory(formProvider.logoEmpresa,
              fit: BoxFit.fitWidth),
    ),

If you have any question, please ask and I'll do my best to help.