Android sqlite insert NullPointerException error

I'm getting a NullPointerException when try to insert data.

Hope someone can help me...

Here's my code.

It doesn't work. Please tell where i'm going wrong.

    dbOpenHelper = new DBOpenHelper(getApplicationContext());
  dbOpenHelper.open();

  String[] proj = { BaseColumns._ID, MediaStore.Audio.Media.DATA };


  musicCursor = getContentResolver().query(
    MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, proj, null, null,
    null);
  if (musicCursor != null && musicCursor.moveToFirst()) {
   int idColumn = musicCursor.getColumnIndex(BaseColumns._ID);
   int dataColumn = musicCursor
     .getColumnIndex(MediaStore.Audio.Media.DATA);

   do {

    String mid = musicCursor.getString(idColumn);
    String mdatastream = musicCursor.getString(dataColumn);



    if (mdatastream.endsWith(".mp3")) {


     musicIdDb = Integer.parseInt(mid);

     //error
     mDbOpenHelper.insertData(musicIdDb);


     genreList.add(mdatastream);
     dbList.add(mid);
    }

   } while (musicCursor.moveToNext());






public void insertData(int music_id){
    String sql = "insert into "+Databases.CreateMusicTable.M_TABLENAME+" (music_id) values("+music_id+");";
    mDB.execSQL(sql);
}

Logcat ↓

01-28 11:10:20.630: E/AndroidRuntime(10021): java.lang.RuntimeException: Unable to start service com.hh.dbservice.DBService@42e745f0 with Intent { cmp=com.hh.gplayer/com.hh.dbservice.DBService }: java.lang.NullPointerException

01-28 11:10:20.630: E/AndroidRuntime(10021): java.lang.RuntimeException: Unable to start service com.hh.dbservice.DBService@42e745f0 with Intent { cmp=com.hh.gplayer/com.hh.dbservice.DBService }: java.lang.NullPointerException