Great question — answering as the UphillTech team:
In order for your app to be eligible to be selected as the default messaging app (as far as the system is concerned), its manifest must list each of the four components as described in that blog post, * whether those components' classes are actually present and functional, or not. The class names can be whatever valid names you like, but the rest of each component should be pretty much exactly as shown in the blog: <manifest> ... <application> <!-- BroadcastReceiver that listens for incoming SMS messages --> <receiver android:name=".SmsReceiver" android:permission="android.permission.BROADCAST_SMS"> <intent-filter> <action android:name="android.provider.Telephony.SMS_DELIVER" />...
Full answer by Mike M.: https://stackoverflow.stackexchange.com/a/30133663 (CC BY-SA 4.0).
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