1) Implement function to import SMS messages from the system's default SMS database into a secure local SMS database in an existing Android chat app. The import function and secure SMS database should work the same way as Signal Android messenger app: [login to view URL]
See attached screenshots of the UI concept for the import screen and import dialog.
2) Replace existing calls to sync with the system's default SMS database so that the new local secure SMS database is used instead. For example, the 'Delete SMS' function should remove from the local secure 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, such that incoming SMS are received directly into the local secure SMS database instead of the system's default SMS database. This should work even when the app is in stopped state, by being able to process the SMS_DELIVER broadcast.