How to convert Uint8List image to File Image for upload in flutter web

问题

I have have been able to pick a file from my computer and display in my flutter web app. I have a function(of type File) which takes a file and uploads it to the server. like so functionName(File imageToSend).

But when I try to send this image to the sever side, it gives me an error. Am doing the upload using the code below:

Uint8List uploadedImage;
File theChosenImg;
FileReader reader =  FileReader();
FileReader reader2 = FileReader();

filePicker() 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];    

    reader.onLoadEnd.listen((e) {
                setState(() {
                  uploadedImage = reader.result;
                  theChosenImg = files[0];
                });
    });
    reader.readAsArrayBuffer(file);
    reader2.readAsDataUrl(file);
  }
});
}

when I use the variable uploadedImage the error is Expected a value of type 'File', but got one of type 'String' then I decided to use theChosenImg from theChosenImg = files[0];, this also tell me that the datatypes mismatch.

Is it possible for me to convert the Uint8List datatype to File?

UPDATED WITH CODE

import 'dart:typed_data';
import 'dart:html';
import 'dart:ui' as ui;
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:web_image_upload/impUp.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

class FrontUi extends StatefulWidget {
  @override
  _FrontUiState createState() => _FrontUiState();
}

class _FrontUiState extends State<FrontUi> {

Uint8List uploadedImage;
File theChosenImg;
String dispText = 'Uploaded image should shwo here.';
FileReader reader2 = FileReader();

_startFilePicker() 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) {
                setState(() {
                  uploadedImage = reader.result;
                  theChosenImg = files[0];
                });
    });
    reader.readAsArrayBuffer(file);
    reader2.readAsDataUrl(file);
  }
});
}

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: ListView(
          children: <Widget>[
            Column(
              children: <Widget>[
                SizedBox(
                  height: 30,
                ),
                Container(
                  height: 500,
                  width: 800,
                  child: Center(
                    child: uploadedImage == null
                ? Container(
                    child: Text(dispText),
                  )
                : Container(
                    child: Image.memory(uploadedImage),
                  ),
                  ),
                ),
            SizedBox(height: 20,),                
                CupertinoButton(
                  color: Colors.green,
                  child: Text("Choose"),
                  onPressed: (){
                    _startFilePicker();
                  },
                ),

            SizedBox(height: 50,),
             CupertinoButton(
              color: Colors.green,
              child: Text("Upload"),
              onPressed: (){
                PhotoCls().upload(reader2.result);
              },
            ),



              ],
            ),



          ],
        ),
      ),

    );
  }
}

Class with The MEDTHOD WHICH SENDS THE IMAGE

import 'dart:io';
import 'package:path/path.dart';
import 'package:async/async.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';



  class PhotoCls {
 String phpEndPoint = "http://IPv4 address/testlocalhost/uploadPicture.php";


upload(File imageFile) async {    
      // open a bytestream
      var stream = new http.ByteStream(DelegatingStream.typed(imageFile.openRead()));
      // get file length
      var length = await imageFile.length();

      // string to uri
      var uri = Uri.parse(phpEndPoint);

      // create multipart request
      var request = new http.MultipartRequest("POST", uri);

      // multipart that takes file
      var multipartFile = new http.MultipartFile('file', stream, length,
          filename: basename(imageFile.path));

      // add file to multipart
      request.files.add(multipartFile);

      // send
      var response = await request.send();
      print(response.statusCode);

      // listen for response
      response.stream.transform(utf8.decoder).listen((value) {
        print(value);
      });
    }



  }

回答1:

File.fromRawPath(Uint8List uint8List);

来源：https://stackoverflow.com/questions/58793993/how-to-convert-uint8list-image-to-file-image-for-upload-in-flutter-web

标签

Flutter

dart

flutter-web