JavaFX GridPane col/row span vs index

I'm learning JavaFX through the Oracle Tutorial and I'm confused about this particular topic. I seem to be the only one confused as my searching hasn't led to any helpful results. I'm creating a basic GridPane with 2 columns (0,1) and 3 rows (0,1,2). In the first row I have the title, and the other two rows have a label on the left and a text box on the right -- it's a login screen

Here's the code for populating the grid:

    Text scenetitle = new Text("Login");
    scenetitle.setFont(Font.font("Tahoma", FontWeight.NORMAL, 20));
    grid.add(scenetitle,0,0,2,1); // Row span here is set to 1

    Label userName = new Label("User Name");
    grid.add(userName,0,1);

    TextField userTField = new TextField();
    grid.add(userTField,1,1);

    Label passName = new Label("Password");
    grid.add(passName,0,2); // Here I'm referencing a row index of 2

    TextField passTField = new TextField();
    grid.add(passTField,1,2)

The code works perfectly, as it's basically just a copy-paste from the tutorial. However, my confusion comes from the fact that I have a row span of 1, but I'm referencing a row index of 2. I tried switching the row and column span but that messed it up, so I'm sure this is correct. What am I missing?

Solution

It is different.First of all it is usefull to:

      setGridLinesVisible(true);

so you can see what is going on with the grid layout(the space between columns and rows the width and height of elements etc). About add method from documentation:

add(Node child,int columnIndex,int rowIndex,int colspan,int rowspan)

In the first line:

       grid.add(scenetitle,0,0,2,1);

you add the element scenetitle and it will be positioned on column 0 and row 0 and it has the possibility to span 2 columns and 1 row

In the finish line:

      grid.add(passName,0,2);

you add the element passName and it will be positioned on column 0 and row 2 ,you have not given values about how it can span.

A special situation

In GridPane if for example you have an item on column 0 and row 0 with row span 4,and in the second line an item with not default span given it will span the maximum of the spans (in this example 4).