dependencies:
  flutter:
    sdk: flutter


  # new
  amplify_core: '<1.0.0'
  amplify_auth_cognito: '<1.0.0'
  amplify_storage_s3: '<1.0.0'

  # we happen to also use this in our demo
  file_picker: ^1.13.3

  ## this is also available if you want analytics but not covered in this post
  # amplify_analytics_pinpoint: '<1.0.0'

npm i -g @aws-amplify/cli@4.26.1-flutter-preview.0

# command
amplify init

# prompts
? Enter a name for the environment
    `dev`
? Choose your default editor:
    `IntelliJ IDEA`
? Choose the type of app that you're building: 
    'flutter'
⚠️  Flutter project support in the Amplify CLI is in DEVELOPER PREVIEW.
Only the following categories are supported:
 * Auth
 * Analytics
 * Storage
? Where do you want to store your configuration file? 
    ./lib/
? Do you want to use an AWS profile?
    `Yes`
? Please choose the profile you want to use
    `default`

# command
amplify add storage

# prompts
? Please select from one of the below mentioned services:
    `Content (Images, audio, video, etc.)`
? You need to add auth (Amazon Cognito) to your project in order to add storage for user files. Do you want to add auth now?
    `Yes`
? Do you want to use the default authentication and security configuration?
    `Default configuration`
? How do you want users to be able to sign in?
    `Username`
? Do you want to configure advanced settings?
    `No, I am done.`
? Please provide a friendly name for your resource that will be used to label this category in the project:
    `S3friendlyName`
? Please provide bucket name:
    `storagebucketname`
? Who should have access:
    `Auth and guest users`
? What kind of access do you want for Authenticated users?
    `create/update, read, delete`
? What kind of access do you want for Guest users?
    `create/update, read, delete`
? Do you want to add a Lambda Trigger for your S3 Bucket?
    `No`

amplify push --y

import 'package:amplify_auth_cognito/amplify_auth_cognito.dart';
import 'package:amplify_core/amplify_core.dart';
import 'package:amplify_storage_s3/amplify_storage_s3.dart';
import 'amplifyconfiguration.dart';
// etc

// inside of some class for the page
  Amplify amplify = Amplify();
  bool _isAmplifyConfigured = false;

  @override
  initState() {
    super.initState();
    _initAmplifyFlutter();
  }

  void _initAmplifyFlutter() async {
    AmplifyAuthCognito auth = AmplifyAuthCognito();
    AmplifyStorageS3 storage = AmplifyStorageS3();
    amplify.addPlugin(
        authPlugins: [auth],
        storagePlugins: [storage],
    );
    await amplify.configure(amplifyconfig);

    setState(() {
      _isAmplifyConfigured = true;
    });
  }

import 'package:amplify_auth_cognito/amplify_auth_cognito.dart';
import 'package:amplify_core/amplify_core.dart';
import 'package:flutter/material.dart';

class SignInView extends StatefulWidget {
  @override
  _SignInViewState createState() => _SignInViewState();
}

class _SignInViewState extends State<SignInView> {
  final usernameController = TextEditingController();
  final passwordController = TextEditingController();

  String _signUpError = "";
  List<String> _signUpExceptions = [];

  @override
  void initState() {
    super.initState();
  }

  void _signIn() async {
    // Sign out before in case a user is already signed in
    // If a user is already signed in - Amplify.Auth.signIn will throw an exception
    try {
      await Amplify.Auth.signOut();
    } on AuthError catch (e) {
      print(e);
    }

    try {
      SignInResult res = await Amplify.Auth.signIn(
          username: usernameController.text.trim(),
          password: passwordController.text.trim());
      Navigator.pop(context, true);
    } on AuthError catch (e) {
      setState(() {
        _signUpError = e.cause;
        _signUpExceptions.clear();
        e.exceptionList.forEach((el) {
          _signUpExceptions.add(el.exception);
        });
      });
    }
  }

// etc for the Widget build

import 'package:flutter/material.dart';
import 'dart:io';
import 'package:file_picker/file_picker.dart';
import 'package:amplify_core/amplify_core.dart';
import 'package:amplify_storage_s3/amplify_storage_s3.dart';

class ImageUploader extends StatelessWidget {
  void _upload(BuildContext context) async {
    try {
      print('In upload');
      // Uploading the file with options
      File local = await FilePicker.getFile(type: FileType.image);
      local.existsSync();
      final key = new DateTime.now().toString();
      Map<String, String> metadata = <String, String>{};
      metadata['name'] = 'filename';
      metadata['desc'] = 'A test file';
      S3UploadFileOptions options = S3UploadFileOptions(
          accessLevel: StorageAccessLevel.guest, metadata: metadata);
      UploadFileResult result = await Amplify.Storage.uploadFile(
          key: key, local: local, options: options);

      print('File uploaded.  Key: ' + result.key);
      Navigator.pop(context, result.key);
    } catch (e) {
      print('UploadFile Err: ' + e.toString());
    }
  }

  @override
  Widget build(BuildContext context) {
    return Column(children: [
      RaisedButton(
        child: Text("Upload Image"),
        onPressed: () {
          _upload(context);
        },
      )
    ]);
  }
}