Returns the current item's index.
The getCurrentItemIndex() function returns the index of current item
within the items of the dataset. The indices of the items in a dataset
are zero-based. For example, if the third item is the current item, then
getCurrentItemIndex() returns 2.
Calling getCurrentItemIndex() on a write-only dataset causes an error.
Returns null if one of the following is true if the dataset:
Note:
A dataset needs to load its data before you call its getCurrentItemIndex() function.
Usually a dataset finishes loading a short time after the page it is on finishes
loading. So if you call getCurrentItemIndex() inside the page’s onReady()
event handler, the dataset might not be ready yet.
To call getCurrentItemIndex() as soon as possible after a page loads, use the dataset's
onReady() function inside the page’s onReady()
event handler to ensure that both the page and the dataset have finished loading.
If the current item is changed from a non-dataset source, such as by
selecting a row in a table connected to a dataset or clicking a button set
to advance to the next item in a dataset, the dataset's current item is
not updated immediately. Therefore, to get the dataset's new current item index,
call getCurrentItemIndex() in the dataset's onCurrentIndexChanged()
event handler. Do not use the events of the non-dataset source, such as
onRowSelect or onClick,
to call getCurrentItemIndex() because they will fire before the dataset's
current item is updated.