android NullPointerException when executing query on SQLite database

Question

I'm trying to read data out of a database I created, but I always get a NullPointerException when trying to fetch all my records.

I practically copypasted the code from another application I have running perfectly, but somehow I'm doing it wrong here.

The NullPointerException is at the line of

return mDb.query(DATABASE_TABLE_LOCALLOGIN, new String[] {LOCALLOGIN_ID, LOCALLOGIN_LOGIN, LOCALLOGIN_PASSWORD}, null, null, null, null, null);

Here's the relevant code (don't mind the string arrays, its for adding tables later on: GoingOutDbAdapter.java

public class GoingOutDbAdapter {
private static final String DATABASE_NAME = "GoingOutData";
private static final String DATABASE_TABLE_LOCALLOGIN = "LocalLogin";

public static final String LOCALLOGIN_ID = "LocalLogin_id";
public static final String LOCALLOGIN_LOGIN = "Login";
public static final String LOCALLOGIN_PASSWORD = "Password";

private static final String TAG = "Debugstring";

private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;

private static final String[] DATABASE_CREATE = {
    "CREATE Table " + DATABASE_TABLE_LOCALLOGIN + " ( "
    + LOCALLOGIN_ID + " integer PRIMARY KEY Autoincrement, "
    + LOCALLOGIN_LOGIN + " text NOT NULL, "
    + LOCALLOGIN_PASSWORD + " text NOT NULL );"};

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) {
        for(int i = 0; i < DATABASE_CREATE.length; i++){
            Log.d(TAG,DATABASE_CREATE[i]);
            db.execSQL(DATABASE_CREATE[i]);
        }   
    }
}

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

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

public void close() {
    mDbHelper.close();
}

public Cursor fetchAllLocalLogins() {
    return mDb.query(DATABASE_TABLE_LOCALLOGIN, new String[] {LOCALLOGIN_ID, LOCALLOGIN_LOGIN, LOCALLOGIN_PASSWORD}, null, null, null, null, null);
}

}

MyActivity.java, where I call fetchAllLocalLogins

public class MyActivity extends Activity {
/** Called when the activity is first created. */   

private GoingOutDbAdapter mDbHelper;

@Override
public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    mDbHelper = new GoingOutDbAdapter(this);

    setContentView(R.layout.main);

Cursor localLogin = mDbHelper.fetchAllLocalLogins();

}
}

user · Accepted Answer · 2012-04-09 09:10:05Z

11

You'll probably want to call the open() method before you make the query:

//...
mDbHelper.open(); //whitout this call mdb will be NULL
Cursor localLogin = mDbHelper.fetchAllLocalLogins();

answered Apr 9, 2012 at 9:10

user

87.1k18 gold badges200 silver badges190 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Mats Raemen Over a year ago

Did that, now I get "android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1" at "mLoginField.setText(localLogin.getString(localLogin.getColumnIndexOrThrow(GoingOutDbAdapter.LOCALLOGIN_LOGIN)));" with mLoginField being an EditText in my contentview

user Over a year ago

@MatsRaemen The Cursor that you are returning from a query is positioned at -1 so you should always call localLogin.moveToFirst() or localLogin.moveToNext() before you attempt to get data.

Deminetix Over a year ago

Its easy to forget to open it... I built a helper class that opens in the constructor :)

Srikanth · Accepted Answer · 2012-04-09 09:40:25Z

1

You should open the database before performing the database operation. mDbHelper.open();

answered Apr 9, 2012 at 9:40

Srikanth

1642 silver badges9 bronze badges

Collectives™ on Stack Overflow

android NullPointerException when executing query on SQLite database

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related