Question

I have an android application using an SQLite database. I open the database when the application starts, but never close it as it is in constant use.

What is the best way to tell the database to flush all its changes to permanent storage? Do I need to just close it and re-open or is there a more efficient way?

My problem is that when testing on a phone, turning the phone off after a number of writes sometimes causes the database to loose the most recent updates when the application is restarted, which is obviously unacceptable for a database system.

Since I cannot find out how to capture the application close event I cannot know when to manually close the database.

Answer 1

I open the database when the application starts, but never close it as it is in constant use.

Don’t do that. You are apparently ignoring all the errors that are appearing in LogCat complaining that you are leaking database connections.

What is the best way to tell the
database to flush all its changes to
permanent storage?

It will do that automatically at the end of a transaction. By default, each individual SQL operation (e.g., insert) is a transaction.

Do I need to just close it and re-open
or is there a more efficient way?

You should close your database at some point (e.g., onDestroy() of the service that is mediating your database).

My problem is that when testing on a
phone, turning the phone off after a
number of writes sometimes causes the
database to loose the most recent
updates when the application is
restarted, which is obviously
unacceptable for a database system.

If you can create a sample project that demonstrates the problem even after you are properly closing your database connection, post it to the Android issue tracker.

Since I cannot find out how to capture
the application close event I cannot
know when to manually close the
database.

Close it when all activities have unbound from the service that is mediating the database connection, triggering that service’s onDestroy() method.

Or, open a fresh connection in each component that needs access to the database, and use Java synchronization to ensure two threads do not try to simultaneously use the database (if needed).