upload_selected_file.dart

import 'dart:io';
import 'package:file_picker/file_picker.dart';
import 'package:flutter/material.dart';
import 'package:firebase_storage/firebase_storage.dart' as firebase_storage;
import 'package:path/path.dart';
import 'package:path_provider/path_provider.dart';

class FileUpload extends StatefulWidget {
  FileUpload({Key? key}) : super(key: key);

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

class _FileUploadState extends State<FileUpload> {
  firebase_storage.FirebaseStorage storage =
      firebase_storage.FirebaseStorage.instance;

  File? file;

  selectFile() async {
    final result = await FilePicker.platform.pickFiles(allowMultiple: false);
    if (result == null) return;
    final path = result.files.single.path;
    setState(() => file = File(path));
  }

  Future uploadFile() async {
    if (file == null) return;
    final fileName = basename(file!.path);
    final destination = 'files/$fileName';

    try {
      final ref = firebase_storage.FirebaseStorage.instance
          .ref(destination)
          .child('file/');
      await ref.putFile(file!);
      final urlString = ref.getDownloadURL();
      print('Url $urlString');
      return urlString;
    } catch (e) {
      // e.g, e.code == 'canceled'
    }
  }

  @override
  Widget build(BuildContext context) {
    final fileName = file != null ? basename(file!.path) : 'No File Selected';
    return Scaffold(
      backgroundColor: Colors.white,
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Container(
              child:
                  TextButton(onPressed: selectFile, child: Text('Select File')),
            ),
            Text(
              fileName,
              style: TextStyle(fontSize: 16, fontWeight: FontWeight.w500),
            ),
            Container(
              child:
                  TextButton(onPressed: uploadFile, child: Text('Upload File')),
            ),
          ],
        ),
      ),
    );
  }
}