android / JAVA - 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.

DB Insert

  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());

Insert Method

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

Log:

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

I tried

 public long insertDataId(int music_id){
        mDB = mDBHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("music_id", music_id);
        return mDB.insert(Databases.CreateMusicTable.M_TABLENAME, null, values);
    }

but... NullPointerException too. Thanks.