I got same exception in 2024. I have named everything properly, but still had this error. The problem was that new version of android build system shrinks unused resources.

As per flutter_local_notifications, Android Setup -> Release build configuration to fix this you should do following:

1. Add keep.xml to android/app/src/main/res/raw. And list there resources you want to keep (e.g. some icon)
2. Also setup proguard-rules.pro to prevent "Missing type" errors.

NOTE: this guideline might be outdated by the time you're reading this. Prefer to official flutter_local_notifications guidelines instead.