1) Implement function to import SMS messages from the system's default SMS database into a local SMS database in an existing Android chat app. The import function should work the same way as Signal Android messenger app: [login to view URL]
Note: MMS functions are not required.
See attached screenshots of the UI concept for the import screen and import dialog taken from Signal messenger app.
2) Remove existing calls to sync with the system's default SMS database and replace these with the local SMS database instead. Opening a specific chat/conversation should no longer load SMS individually for that chat/conversation because all SMS are imported by the new import function. The 'Delete SMS' function should delete from the local SMS database instead of the system's default SMS database (and vice versa if deleting from the system's default SMS app).
3) Make the app function as the system's default SMS app when set as the default app, such that incoming SMS are received directly into the local SMS database instead of going to the system's default SMS database. This should work even when the app is in stopped state by processing the SMS_DELIVER broadcast.