[SOLVED] How to correctly set redirect

I'm trying to log the user into a Google API from my Flutter app, but can't get it to automatically fetch the token. The closest I got was to see the token string in the auth screen and be asked to copy/paste it back into the app. I suspect it's related to the redirect_uri parameter.

I attempted with both oauth2_client and flutter_appauth and it's pretty much the same outcome. When setting up the client, if I use the first redirect_uri provided by Google urn:ietf:wg:oauth:2.0:oob, after granting the permissions it shows the token in the auth screen and instructs the user to copy it and paste it back in the app. If I use the uri that I set in AndroidManifest.xml and build.gradle, instead of the consent screen, I get this message in the browser:

"Invalid parameter value for redirect_url: Missing scheme: ai.autonet.afterme"

Lastly, if I use "http://localhost" (the second uri provided by Google), I get "request timed out".

My client configuration from Google's side looks like this:

"client_id":"somethingsomething.apps.googleusercontent.com","project_id":"afterme-850af","auth_uri":"https://accounts.google.com/o/oauth2/auth","token_uri":"https://oauth2.googleapis.com/token","auth_provider_x509_cert_url":"https://www.googleapis.com/oauth2/v1/certs","redirect_uris":["urn:ietf:wg:oauth:2.0:oob","http://localhost"]

Here is the simplest version of the flutter_appauth implementation:

main.dart
import 'package:flutter/material.dart';
    import 'package:flutter_appauth/flutter_appauth.dart';
    import 'package:oauth2_client/access_token_response.dart';
    import 'package:http/http.dart' as http;

    const AUTH_ENDIPOINT = 'https://accounts.google.com/o/oauth2/auth';
    const CLIENT_ID =
        'somethingsomething.apps.googleusercontent.com';
    const REDIRECT_URI = 'ai.autonet.afterme';
    const TOKEN_ENDPOINT = "https://oauth2.googleapis.com/token";
    var scopes = [
        "https://www.googleapis.com/auth/youtube",
        "https://www.googleapis.com/auth/youtube.upload",
    ];
    void main() {
        runApp(MyApp());
    }

    var httpClient = http.Client();

    class MyApp extends StatelessWidget {
        @override
        Widget build(BuildContext context) {
        return MaterialApp(
            title: 'Flutter Demo',
            theme: ThemeData(
            primarySwatch: Colors.blue,
            visualDensity: VisualDensity.adaptivePlatformDensity,
            ),
            home: MyHomePage(title: 'Flutter Demo Home Page'),
        );
        }
    }

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

        final String title;
        FlutterAppAuth appAuth = FlutterAppAuth();

        authorize() async {
        final AuthorizationTokenResponse result =
            await appAuth.authorizeAndExchangeCode(AuthorizationTokenRequest(
                CLIENT_ID, REDIRECT_URI,
                serviceConfiguration: AuthorizationServiceConfiguration(
                    AUTH_ENDPOINT,
                    TOKEN_ENDPOINT),
                scopes: scopes));
        print(result.accessToken.toString());
        }

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

    class _MyHomePageState extends State<MyHomePage> {
        getResources() async {
        http.Response resp = await httpClient
            .get('GET https://www.googleapis.com/youtube/v3/videos');
        print(resp.body);
        }


        @override
        Widget build(BuildContext context) {
        return Scaffold(
            appBar: AppBar(
            title: Text(widget.title),
            ),
            body: Center(
            child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                
                RaisedButton(
                    child: Text("Permission"), onPressed: () => widget.authorize()),
                ],
            ),
            ),
            
        );
        }
    }
----------------------------------------------------------------
AndroidManifest.xml:
        <manifest xmlns:android="http://schemas.android.com/apk/res/android"
            package="ai.autonet.afterme">
            
            <!-- io.flutter.app.FlutterApplication is an android.app.Application that
                calls FlutterMain.startInitialization(this); in its onCreate method.
                In most cases you can leave this as-is, but you if you want to provide
                additional functionality it is fine to subclass or reimplement
                FlutterApplication and put your custom class here. -->
            <application
                android:name="io.flutter.app.FlutterApplication"
                android:label="afterme"
                android:icon="@mipmap/ic_launcher">
                <activity android:name="com.linusu.flutter_web_auth.CallbackActivity" >
                <intent-filter android:label="flutter_web_auth">
                    <action android:name="android.intent.action.VIEW" />
                    <category android:name="android.intent.category.DEFAULT" />
                    <category android:name="android.intent.category.BROWSABLE" />
                    <data android:scheme="ai.autonet.afterme" />
                </intent-filter>
            </activity>
                <activity
                    android:name=".MainActivity"
                    android:launchMode="singleTop"
                    android:theme="@style/LaunchTheme"
                    android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
                    android:hardwareAccelerated="true"
                    android:windowSoftInputMode="adjustResize">
                    <!-- Specifies an Android theme to apply to this Activity as soon as
                        the Android process has started. This theme is visible to the user
                        while the Flutter UI initializes. After that, this theme continues
                        to determine the Window background behind the Flutter UI. -->
                    <meta-data
                    android:name="io.flutter.embedding.android.NormalTheme"
                    android:resource="@style/NormalTheme"
                    />
                    <!-- Displays an Android View that continues showing the launch screen
                        Drawable until Flutter paints its first frame, then this splash
                        screen fades out. A splash screen is useful to avoid any visual
                        gap between the end of Android's launch screen and the painting of
                        Flutter's first frame. -->
                    <meta-data
                    android:name="io.flutter.embedding.android.SplashScreenDrawable"
                    android:resource="@drawable/launch_background"
                    />
                    <intent-filter>
                        <action android:name="android.intent.action.MAIN"/>
                        <category android:name="android.intent.category.LAUNCHER"/>
                    </intent-filter>
                </activity>
                <!-- Don't delete the meta-data below.
                    This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
                <meta-data
                    android:name="flutterEmbedding"
                    android:value="2" />
            </application>
        </manifest>
-------------------------------------------------------------------------------------
build.gradle:
  ...
    defaultConfig {
        applicationId "ai.autonet.afterme"
        minSdkVersion 18
        targetSdkVersion 29
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
        manifestPlaceholders = [
        'appAuthRedirectScheme': 'ai.autonet.afterme'
        ]
    }
    ...

How to correctly set redirect_uri in Flutter app?