How to upload Files using Flutter Web (Python Server)

Question

I am trying to upload multiple files through a Flutter frontend, possibly to a Python server. I have not found any working code on how to upload files through Flutter Web. My frontend code is according an answer here: How to Pick files and Images for upload with flutter web

import 'package:http/http.dart' as http;
import 'package:file_picker/file_picker.dart';
import 'package:flutter/material.dart';

void main() {
  /// your app lunch from here
  runApp(new MaterialApp(
    //// remove debug logo  top left AppBar
    debugShowCheckedModeBanner: false,
//    application title
    title: 'Hello World',
//     whole  content
    home: TabsExample(),
  ));
}

class TabsExample extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState

    return TabsState();
  }
}

class TabsState extends State<TabsExample> {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build

    return DefaultTabController(
        length: 1,
        child: new Scaffold(
          appBar: AppBar(
            title: Text('Test Tab'),
            bottom: TabBar(tabs: [
              Tab(
                icon: Text(
                  'Test',
                ),
              ),
            ]),
          ),
          body: TabBarView(children: [
            new FileUploadWithHttp(),
          ]),
        ));
  }
}

class FileUploadWithHttp extends StatefulWidget {
  @override
  _FileUploadWithHttpState createState() => _FileUploadWithHttpState();
}

class _FileUploadWithHttpState extends State<FileUploadWithHttp> {
  PlatformFile objFile;
  PlatformFile result;

  void chooseFileUsingFilePicker() async {
    //-----pick file by file picker,

    var result = await FilePicker.platform.pickFiles(
        withReadStream:
            true, // this will return PlatformFile object with read stream
        allowMultiple: true);
    print(result.files.length);
    print(result.names);
    // print(result.files.first.path); //not supported on web
    if (result != null) {
      setState(() {
        objFile = result.files[0];
        //print(objFile.readStream);
      });
    }
  }

  void uploadSelectedFile() async {
    //---Create http package multipart request object
    final request = http.MultipartRequest(
      "POST",
      Uri.parse("http://localhost:8000"), // e.g. localhost
    );
    //-----add other fields if needed
    //request.fields["id"] = "abc";

    //-----add selected file with request
    request.files.add(new http.MultipartFile(
        "file", objFile.readStream, objFile.size,
        filename: objFile.name));

    //-------Send request
    var resp = await request.send();

    //------Read response
    String result = await resp.stream.bytesToString();

    //-------Your response
    print(result);
    print('Upload successfull!');
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Column(
        children: [
          //------Button to choose file using file picker plugin
          ElevatedButton(
              child: Text("Choose File"),
              onPressed: () => chooseFileUsingFilePicker()),
          //------Show file name when file is selected
          if (objFile != null) Text("File name : ${objFile.name}"),
          //------Show file size when file is selected
          if (objFile != null) Text("File size : ${objFile.size} bytes"),
          //------Show upload utton when file is selected
          ElevatedButton(
              child: Text("Upload"), onPressed: () => uploadSelectedFile()),
        ],
      ),
    );
  }
}

Running this on a python server according to this suggestion: https://gist.github.com/UniIsland/3346170

Or any other one that i've tried does not work, the server is not able to recieve the file properly. The error message is:

(False, "Can't find out file name...", 'by: ', ('::1', 62868, 0, 0))

Is there any straighforward way (possibly with code) on how to upload the file? Or do you have an idea why this error is coming? Any help would be greatly appreciated!

Answer 1

follow this, it might help you.

import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';
import 'dart:io';
import 'package:path/path.dart';
import 'package:dio/dio.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  File _image;
  final GlobalKey<ScaffoldState> _scaffoldstate =
      new GlobalKey<ScaffoldState>();

  Future getImage() async {
    var image = await ImagePicker.pickImage(source: ImageSource.camera);
    _uploadFile(image);

    setState(() {
      _image = image;
    });
  }

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  // Methode for file upload
  void _uploadFile(filePath) async {
    // Get base file name
    String fileName = basename(filePath.path);
    print("File base name: $fileName");

    try {
      FormData formData =
          new FormData.from({"file": new UploadFileInfo(filePath, fileName)});

      Response response =
          await Dio().post("http://192.168.0.101/saveFile.php", data: formData);
      print("File upload response: $response");

      // Show the incoming message in snakbar
      _showSnakBarMsg(response.data['message']);
    } catch (e) {
      print("Exception Caught: $e");
    }
  }

  // Method for showing snak bar message
  void _showSnakBarMsg(String msg) {
    _scaffoldstate.currentState
        .showSnackBar(new SnackBar(content: new Text(msg)));
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      key: _scaffoldstate,
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: _image == null ? Text('No image selected.') : Image.file(_image),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: getImage,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}