Query if Adroid DB exists!

Question

Hello all,

I have created a database for my android app which contains static data and does not require update/delete functionality thus when the app starts, I want to check if the db exists and if not then execute my dbAdapter class. I know its a simple if statement but I was just wondering the most efficient way to query whether the db exists.

Cheers

Answer 1

/**
 * Check if the database exist
 * 
 * @return true if it exists, false if it doesn't
 */
private boolean checkDataBase() {
    SQLiteDatabase checkDB = null;
    try {
        checkDB = SQLiteDatabase.openDatabase(DB_FULL_PATH, null,
                SQLiteDatabase.OPEN_READONLY);
        checkDB.close();
    } catch (SQLiteException e) {
        // database doesn't exist yet.
    }
    return checkDB != null ? true : false;
}

where DB_FULL_PATH is the path to your database file

Answer 2

When you initialize the below class with:

mOpenHelper = new DatabaseHelper(getContext());

That will automatically create the database if it is not present. It also allows you upgrade the database by changing the DB_VER to a higher number.

Then so you are able to query the database use:

 SQLiteDatabase db = mOpenHelper.getWritableDatabase();

the above gets you db.query() db.insert() etc methods.

private static class DatabaseHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "db_name.db";
    private static final int DB_VER = 1;

    public DatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VER);

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL("CREATE TABLE table_name (" + "_id INTEGER PRIMARY KEY, "
                + " column_name_2 TEXT );");


                .execSQL("INSERT INTO table_name "
                        + "(column_name_2) "
                        + "VALUES " + "('hello world');");


    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        Log.w(TAG + "Upgrading database from version " + oldVersion + " to "
                + newVersion + ", which will destroy all old data");
        try {
            db.execSQL("DROP TABLE IF EXISTS table_name");
            onCreate(db);

        } catch (SQLException e) {
            Log.e(TAG + "getting exception "
                    + e.getLocalizedMessage().toString());
        }
    }

}