Multiple Table SQLite DB Adapter(s) in Android?

Question

I was reading the Android SQLite NotePad tutorial that referenced creating a DB Adapter class to create and access a DB table. When dealing with a multi-table SQLite Database, is it best practice to create a different Adapter Class for each table or create a single DB Adapter class for the entire Android Application?

My application uses multiple tables and I was hoping not to have to have a single massive adapter class. the problem, however, is that I have a nested subclass of SQLiteOpenHelper per the NotePad Example within each adapter. When the first table is accessed, everything works fine. When I then try to access the second tble(from a different activity) my app crashes.

At first, I thought the crash was being caused by a versioning issue, but both adapters now have the same database version and it's still crashing.

Here's an example of one of the DB Adapters for the table. The other adapters all follow the same format with varying implementations.

public class InfoDBAdapter {
    public static final String ROW_ID = "_id";
    public static final String NAME = "name";

    private static final String TAG = "InfoDbAdapter";
    private static final String DATABASE_NAME = "myappdb";
    private static final String DATABASE_TABLE = "usersinfo";
    private static final int DATABASE_VERSION = 1;


    private static final String DATABASE_CREATE = "create table usersinfo (_id integer primary key autoincrement, "
            + NAME
            + " TEXT," + ");";

    private DatabaseHelper mDbHelper;
    private SQLiteDatabase mDb;

    private final Context mCtx;

    private static class DatabaseHelper extends SQLiteOpenHelper {

        DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {

            db.execSQL(DATABASE_CREATE);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to " //$NON-NLS-1$//$NON-NLS-2$
                    + newVersion + ", which will destroy all old data"); //$NON-NLS-1$
            //db.execSQL("DROP TABLE IF EXISTS usersinfo"); //$NON-NLS-1$
            onCreate(db);
        }
    }


    public InfoDBAdapter(Context ctx) {
        this.mCtx = ctx;
    }


    public InfoDBAdapter open() throws SQLException {
        this.mDbHelper = new DatabaseHelper(this.mCtx);
        this.mDb = this.mDbHelper.getWritableDatabase();
        return this;
    }

    /**
     * close return type: void
     */
    public void close() {
        this.mDbHelper.close();
    }


    public long createUser(String name) {
        ContentValues initialValues = new ContentValues();
        initialValues.put(NAME, name);
        return this.mDb.insert(DATABASE_TABLE, null, initialValues);
    }


    public boolean deleteUser(long rowId) {

        return this.mDb.delete(DATABASE_TABLE, ROW_ID + "=" + rowId, null) > 0; //$NON-NLS-1$
    }


    public Cursor fetchAllUsers() {

        return this.mDb.query(DATABASE_TABLE, new String[] { ROW_ID,
                NAME}, null, null, null, null, null);
    }


    public Cursor fetchUser(long rowId) throws SQLException {

        Cursor mCursor =

        this.mDb.query(true, DATABASE_TABLE, new String[] { ROW_ID, NAME}, ROW_ID + "=" + rowId, null, //$NON-NLS-1$
                null, null, null, null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;

    }


    public boolean updateUser(long rowId, String name) {
        ContentValues args = new ContentValues();
        args.put(NAME, name);
        return this.mDb
                .update(DATABASE_TABLE, args, ROW_ID + "=" + rowId, null) > 0; //$NON-NLS-1$
    }
}

When the first adapter, in this case usersinfo, is accessed, everything works as expected. Let's say I have another adapter for friend info that follows the same structure as above, when it is accessed by a different activity, it would seem to me that the nested subclass of SQLiteOpenHelper would attempt to create the database again. Obviously something is wrong because in that scenario, my app crashes.

So is the standard practice within Android to create a single mammoth db adapter instead of individual adapters per table?

Answer 1

When dealing with a multi-table SQLite Database, is it best practice to create a different Adapter Class for each table or create a single DB Adapter class for the entire Android Application?

To assist anyone else reading this question, here, "Adapter" is not a subclass of android.widget.Adapter, but an arbitrary other Java class.

however, is that I have a nested subclass of SQLiteOpenHelper per the NotePad Example within each adapter

You want to have one SQLiteOpenHelper per database.

When I then try to access the second tble(from a different activity) my app crashes.

Use adb logcat, DDMS, or the DDMS perspective in Eclipse to examine LogCat and see the stack trace associated with your crashes.

So is the standard practice within Android to create a single mammoth db adapter instead of individual adapters per table?

There is no "standard practice" regarding creating arbitrary Java classes, like your "Adapter" class.\