As the title says, I'm experiencing a NullPointerException which occurs at the first getString() in the below method. For debugging I have used DatabaseUtils.dumpCursorToString() to view the cursor and there are values within the cursor but between the if statement and the do statement, something changes. I use this same code in another method in a separate activity and it works flawlessly.
public ArrayList<String> getMusic() {
helper = new DbHelper(context);
db = helper.getReadableDatabase();
String[] cols = new String[]{MUSIC_ID, MUSIC_COUNTRY, MUSIC_BLUES, MUSIC_ROCK, MUSIC_METAL,
MUSIC_HIPHOP, MUSIC_CLASSICAL, MUSIC_PUNK, MUSIC_TECHNO, MUSIC_JAZZ, MUSIC_OTHER};
Cursor c = db.query(TABLE_MUSIC_INT, cols, null, null, null, null, null);
int count = c.getCount();
Log.v("INTEREST CURSOR ", "Count: " + count); // log row count
if (c.moveToFirst()) {
Log.v("INTEREST CURSOR ", DatabaseUtils.dumpCursorToString(c)); // dump cursor values
do {
musicInt.add(c.getString(0));
musicInt.add(c.getString(1));
musicInt.add(c.getString(2));
musicInt.add(c.getString(3));
musicInt.add(c.getString(4));
musicInt.add(c.getString(5));
musicInt.add(c.getString(6));
musicInt.add(c.getString(7));
musicInt.add(c.getString(8));
musicInt.add(c.getString(9));
musicInt.add(c.getString(10));
} while (c.moveToNext());
} else {
Log.e("DB_GET_DATA ", " DB_GET_DATA == null");
}
c.close();
return musicInt;
}
DatabaseUtils.dumpCursorToString(c) output:
01-15 19:57:01.201 6247-6247/us.enyi.enyi D/DB OPEN READ: Successful
01-15 19:57:20.440 6247-6247/us.enyi.enyi V/INTEREST CURSOR: Count: 1
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@2f32900f
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: 0 {
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: _id=1
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: country=null
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: blues=null
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: rock=Rock
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: metal=Metal
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: hiphop=HipHop
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: classical=Classical
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: punk=null
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: techno=Techno
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: jazz=null
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: musicother=Other
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: }
01-15 19:57:27.897 6247-6247/us.enyi.enyi V/INTEREST CURSOR: <<<<<
I've attempted other methods of retrieving the data from a cursor and read countless threads here on SO as well as within Android Docs, without finding anything with a helpful resolution. I don't quite understand why the cursor obviously has values but c.getString() fails on a NPE. Any assistance will be greatly appreciated.
Solution:
Failure to initialize musicInt caused the Cursor to have nowhere to put the data it collected. Declared musicInt as:
ArrayList<String> musicInt;
Instead of:
ArrayList<String> musicInt = new ArrayList<>();
The lesson is ensure you initialize your variables appropriately. You'll pull your hair out like I did otherwise.
I don't see where you declare (or initialize) musicInt. That might be what's causing your NPE.