Android SQLite OnUpgrade错误

Question

I'm currently using an sqlite database for an android app.

Firstly I am wondering if there is a proper way to upgrade a sqlite database based on new information. Currently I have my information stored within a text file with the number of lines for the database as the first line. I read the first line, see how many lines there are in the database. If there are more lines in the text file then I upgrade the database and add everything into the database again.

This is my code currently:

try {
        InputStream is = getResources().getAssets().open("Questions");
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        AssistedMemDB db = new AssistedMemDB(this);
        db.open();
        int tempNum = db.getNumber();
        String line = "";
        line = reader.readLine();
        if (Integer.decode(line) > tempNum) {
            db.close();
            db.upgrade();
            db.open();
            while ((line = reader.readLine()) != "") {
                String list[] = line.split("\\<>");
                db.createEntry(list[0], list[1]);
            }
        }
        db.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

I'm getting an error saying:

java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase

Thank you in advance!

Answer 1

You don't upgrade a database to add new rows to it. You upgrade a database when you have new tables or new columns to add. When adding rows, you just do an insert and put the new data in with the old data.

Also, the db helper automatically takes care of calling onUpgrade for you. All you have to do it increment the db version when you want to change the schema.