Android NullPointerException while retrieving data from SQLite Database and storing it in an Array

Question

I am trying to retrieve string data from a column in database and insert into a string array in android. I have used the following code to retrieve data - (helper.java)

public String[] personslist() {
                // TODO Auto-generated method stub
                int i=0;
                Cursor c=myDataBase.rawQuery("select PersonName from Persons;",null);
                String[] values = {};

            for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
                   values[i] = c.getString(c.getColumnIndex("PersonName"));
                   i++;
                }
            return values;


        }

I have used the following code in "adapter.java" class to return the data returned by personslist().

public String[] plist() {
    // TODO Auto-generated method stub

    String[] persons = mDbHelper.personslist(); //this is line no. 131 in adapter class
    return persons;
}

While I am running the application, it is getting crashed and showwing the following error

09-08 08:23:19.715: E/AndroidRuntime(29373): Caused by: java.lang.NullPointerException
09-08 08:23:19.715: E/AndroidRuntime(29373):    at com.example.fromstart.adapter.plist(adapter.java:131)

The query, when run on sqlitebrowser, it returns four rows of four persons names. But, while running on an application, it is returning NullPointerException. Can you please suggest me, where I might have gone wrong?

Thanks in advance.

Answer 1

mDbHelper is null. That's what's throwing your exception. Make sure it gets initialized.

Answer 2

Check where you are initialzing the mDbHelper. You are doing mDbHelpe.personslist(). and here your mDbHelper could be Null and so nullpointer exception.

Answer 3

Did u do anything similar to this to initialize

Context context;
SQLiteDatabase db = null ;
CallDBHelper dbHelp = null;

       public Constructor(Context context) {
            this.context = context;
            dbHelp = new CallDBHelper(context);
            db = dbHelp.getWritableDatabase();
       }

       Cursor c = db.query(...