How does one check if a table exists in an Android SQLite database?

Question

I have an android app that needs to check if there's already a record in the database, and if not, process some things and eventually insert it, and simply read the data from the database if the data does exist. I'm using a subclass of SQLiteOpenHelper to create and get a rewritable instance of SQLiteDatabase, which I thought automatically took care of creating the table if it didn't already exist (since the code to do that is in the onCreate(...) method).

However, when the table does NOT yet exist, and the first method ran upon the SQLiteDatabase object I have is a call to query(...), my logcat shows an error of "I/Database(26434): sqlite returned: error code = 1, msg = no such table: appdata", and sure enough, the appdata table isn't being created.

Any ideas on why?

I'm looking for either a method to test if the table exists (because if it doesn't, the data's certainly not in it, and I don't need to read it until I write to it, which seems to create the table properly), or a way to make sure that it gets created, and is just empty, in time for that first call to query(...)

EDIT
This was posted after the two answers below:
I think I may have found the problem. I for some reason decided that a different SQLiteOpenHelper was supposed to be created for each table, even though both access the same database file. I think refactoring that code to only use one OpenHelper, and creating both tables inside it's onCreate may work better...

Answer 1

I know nothing about the Android SQLite API, but if you're able to talk to it in SQL directly, you can do this:

create table if not exists mytable (col1 type, col2 type);

Which will ensure that the table is always created and not throw any errors if it already existed.

Answer 2

You mentioned that you've created an class that extends SQLiteOpenHelper and implemented the onCreate method. Are you making sure that you're performing all your database acquire calls with that class? You should only be getting SQLiteDatabase objects via the SQLiteOpenHelper#getWritableDatabase and getReadableDatabase otherwise the onCreate method will not be called when necessary. If you are doing that already check and see if th SQLiteOpenHelper#onUpgrade method is being called instead. If so, then the database version number was changed at some point in time but the table was never created properly when that happened.

As an aside, you can force the recreation of the database by making sure all connections to it are closed and calling Context#deleteDatabase and then using the SQLiteOpenHelper to give you a new db object.

Answer 3

Yep, turns out the theory in my edit was right: the problem that was causing the onCreate method not to run, was the fact that SQLiteOpenHelper objects should refer to databases, and not have a separate one for each table. Packing both tables into one SQLiteOpenHelper solved the problem.