Java 无法从SqLite获取坐标以映射活动

我试图从数据库中获取坐标，以便在地图活动中进行标记。但我总是得到一个空指针异常

这是我的数据库：

String query = "CREATE TABLE "+TABLE_NAME+"("+
                COLUMN_ID+ " INTEGER PRIMARY KEY AUTOINCREMENT, "+
                COLUMN_LAT+ " REAL, "+
                COLUMN_LONG+" REAL, "+
                COLUMN_NUM+ " INTEGER "+
                ");";

这就是我调用函数以在我的MapActivity中获取数据库的lat和long值的方式：

public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    mMap.setMyLocationEnabled(true);
    mMap.getUiSettings().setMyLocationButtonEnabled(true);
    double[] dblat = new double[5];
//this is where I get NullPoint Exception
    dblat=dbHandler.Markerslat();
    double []dblong = new double[5];
     dblong = dbHandler.Markerslong();
    for(int j=0;j<dblat.length;j++) {

        LatLng latLng = new LatLng( dblat[j], dblong[j] );
        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.position( latLng );
        markerOptions.title( "Pothole" );
        markerOptions.icon(BitmapDescriptorFactory.fromResource(R.drawable.potholesmall));
        mMap.addMarker( markerOptions );
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, 10));
        mMap.animateCamera(CameraUpdateFactory.zoomTo(15));

    }
}

public double [] Markerslat(){
    SQLiteDatabase db = getWritableDatabase();

    Cursor cursor = db.rawQuery("SELECT * FROM "+ TABLE_NAME + ";",null);
    cursor.moveToFirst();
    int k = cursor.getCount();
    double []dlatitude= new double[k];
    for(int i=0;i<k;i++){

        dlatitude[i]=cursor.getDouble(1);
        Log.i(TAG, "Entered");
        cursor.moveToNext();
    }
    db.close();

    return dlatitude;

}

public double[] Markerslong(){
    SQLiteDatabase db = getWritableDatabase();

    Cursor cursor = db.rawQuery("SELECT longitude FROM "+ TABLE_NAME +";",null);
    cursor.moveToFirst();
    int k = cursor.getCount();
    double []dlongitude= new double[k];
    cursor.moveToFirst();
    for(int i=0;i<k;i++){

        dlongitude[i]=cursor.getDouble(2);
        cursor.moveToNext();
    }
    db.close();

    return dlongitude;

}

public void onMapReady（谷歌地图谷歌地图）{
mMap=谷歌地图；
mMap.setMyLocationEnabled（真）；
mMap.getUiSettings（）.setMyLocationButtonEnabled（true）；
double[]dblat=新的double[5]；
//这就是我得到NullPoint异常的地方
dblat=dbHandler.Markerslat（）；
double[]dblong=新的双精度[5]；
dblong=dbHandler.Markerslong（）；
对于（int j=0；j