Your logic seems incorrect.
I have below logic in one of my app, which works perfectly.
First you have to prepare the lists and initialize the list view on screen initialize.
On Button1 Click I am first creating list with 20 Items, you can change the value of Number variable. Increment value for increasing the list items.
Rest will do the logic. On list view reaching bottom, it increments the list items by set value of increment variable.
AIA: ImageListViewIncrement.aia (163.0 KB)