Firebase SignIn error only in android release mode

[marchukav]

I have phone sign in with Firebase in my flutter app and it all works perfectly in debug mode both iOS and Android but when in release mode it throws an error only on Android device (physical). iOS still works perfect in release mode.

[+9626 ms] E/flutter (21573): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: type 'Null' is not a subtype of type 'String'
[        ] E/flutter (21573): #0      MethodChannelFirebaseAuth.verifyPhoneNumber.<anonymous closure> (package:firebase_auth_platform_interface/src/method_channel/method_channel_firebase_auth.dart:655)
[        ] E/flutter (21573): #1      _RootZone.runUnaryGuarded (dart:async/zone.dart:1593)
[        ] E/flutter (21573): #2      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:339)
[        ] E/flutter (21573): #3      _DelayedData.perform (dart:async/stream_impl.dart:515)
[        ] E/flutter (21573): #4      _PendingEvents.handleNext (dart:async/stream_impl.dart:620)
[        ] E/flutter (21573): #5      _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:591)
[        ] E/flutter (21573): #6      _microtaskLoop (dart:async/schedule_microtask.dart:40)
[        ] E/flutter (21573): #7      _startMicrotaskLoop (dart:async/schedule_microtask.dart:49)
[        ] E/flutter (21573): 

This is my function

 Future verifyPhoneNumber() async {
    
      try {
        await FirebaseAuth.instance.verifyPhoneNumber(
          phoneNumber: _telNumberController.text,
          verificationCompleted: (PhoneAuthCredential credential) async {
            print('COMPLETED');
          
          },
          verificationFailed: (FirebaseAuthException e) {
            print('FAILED');
          },
          codeSent: (
            String verificationId,
            int? resendToken,
          ) {
            print('CODE SENT');
          },
          codeAutoRetrievalTimeout: (String verificationId) {},
        );
      } catch (e) {
        print(e);
      }
    }

Its passing the phone number correctly but even not reaching any print - neither for verificationCompleted nor verificationFailed
I also tried just to put number as a string to phoneNumber - its the same

What was found on the web and tried

• In my firebase project I have 3 SHA1 and 3 SHA256 keys - 2debug, 2release and 2 Google Play Console. Checked that hundred of times

• I deleted and uploaded a fresh google-service.json

• I run flutter clean

• I checked that Android Device Verification is enabled in Google Dev Console

• I checked that I have OAuth 2.0 Client IDs created in Google Dev Console Credentials - 3 for each SHA1 key (autogenerated by Google)

• I followed all the instructions (tried several times from zero) from here https://docs.flutter.dev/deployment/android#signing-the-app

• I tried deleting keys at all and debug mode shows then the error saying it can't find SHA key in Firebase. So its linked correctly.

Nothing has helped so far - if its android release mode (installed to device or through internal testing Google Play) - its not working and giving this error. Looks like its not even sending a phone number to firebase as non of print statements are shown in log.

Any ideas?

Flutter doctor:
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel master, 3.4.0-19.0.pre.88, on macOS 12.6 21G115 darwin-x64, locale en-CL)
[✓] Android toolchain - develop for Android devices (Android SDK version 32.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 14.0)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2021.3)
[✓] VS Code (version 1.71.2)
[✓] Connected device (3 available)
[✓] HTTP Host Availability

• No issues found!

Any ideas?

UPD
I found that it happens when I change in build.gradle
from
signingConfig signingConfigs.debug
to
signingConfig signingConfigs.release

So something is wrong with the release signinConfig
I do

1. Create an upload keystore
   with this command
   keytool -genkey -v -keystore ~/upload-keystore.jks -keyalg RSA -keysize 2048 -validity 10000 -alias upload
2. Create key.properties in android folder
   storePassword=***
   keyPassword=***
   keyAlias=upload
   storeFile=/Users/amarchuk/upload-keystore.jks
3. Configure signing in gradle
   this code before the android block

def keystoreProperties = new Properties()
def keystorePropertiesFile = rootProject.file('key.properties')
   if (keystorePropertiesFile.exists()) {
       keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
   }

4. And inside the android block

signingConfigs {
       release {
           keyAlias keystoreProperties['keyAlias']
           keyPassword keystoreProperties['keyPassword']
           storeFile keystoreProperties['storeFile'] ? file(keystoreProperties['storeFile']) : null
           storePassword keystoreProperties['storePassword']
       }
   }
   buildTypes {
       release {
           signingConfig signingConfigs.release
       }
   }

What can be wrong?

[marchukav]

Finally! After a week of suffering I found where its coming from In your Google Could Console https://console.cloud.google.com/ - Credentials - API Keys - you have your Android Key. I had it restricted for Android Apps as it should be but there you have to add your SHA1 key and I had only my debug SHA1 key but not the release key. Adding release key solved the issues. Hope it will be helpful for other users