Android app built for release still trying to connect to localhost:8081

Question

I'm trying to get an alpha build of my React Native app on my Android phone, but when I open it, it immediately crashes. Fortunately, it's instrumented so I can see that the errors are all because it's still trying to connect to the metro server, which I would expect from a debug build, but I can't figure out how to prevent these calls in a release build. Here are the errors:

Cannot connect to host http://localhost:8081/inspector/device
Cannot connect to host http://localhost:8081/message

Steps taken:

• I'm generating a signed APK via Android Studio, then sending it to myself and installing on my phone.
• Even though I choose a release build in the "Generate signed Bundle or APK" dialog, I also set the default build variant to "release". This oddly changed the connection attempts from "10.0.0.22" to "localhost" but didn't fix my problem.
• I've tried cleaning the project.
• I've searched the project for any references to localhost or 10.0.0.22 and found nothing that should relate to an Android build.
• Removed Expo updates metadata from AndroidManifest.xml (e.g., expo.modules.updates.EXPO_UPDATES_CHECK_ON_LAUNCH).
• Built an APK in a different project and installed on my phone—it worked as expected.

Possibly pertinent information:

• I began this as an Expo project and ejected a few weeks ago, but Expo seems to have left some cruft behind.

----------- UPDATE July 23 ------------

After a few changes, I've moved onto an error where the 3rd party auth screen won't load. Here's what changed:

• Ran code analyzer in Android Studio and removed some permissions that shouldn't be there: MANAGE_DOCUMENTS, WRITE_SETTINGS, USE_FINGERPRINT
• Also auto-fixed an error where the superclass wasn't called (I forget the exact details and it doesn't appear to be in a file that's under source control because there's nothing in my diff)
• Branched code from a commit a few days ago, before I added launcher icons and a 3rd party monitoring tool.

I still need to debug authentication, but it looks like I've probably moved on to a new issue. I'll still do some digging to see if I can narrow in on what actually caused the issue.

----------- UPDATE Later on July 23 ------------

All is well now, though I don't know what made the difference. Builds got into a strange state after my last update, and I ended up deleting my .gradle folder after reading this. I also updated gradle, and my theory at this point is that the upgrade combined with deleting that folder was the actual fix.

I've re-installed the monitoring software and didn't have any trouble.

Answer 1

Should anybody else run into this, I would look at cleaning up the Android build. Steps I would try in order:

1. From the android folder, run ./gradlew clean, then re-build
2. If that doesn't work, delete the .gradle folder as seen in the accepted answer here
3. Check your gradle version, upgrade if it's out of date