getItemVisibleSize method
Returns the size of the visible part (in pixels) of a certain item in the list view.
The index of the item refers to the index of the underlying list.
The method returns null
if the box of the item cannot be calculated. This happens when the item
isn't yet diplayed or when the state of the list view has been changed via notifications
but these changes are not yet taken into account.
Implementation
_PercentageSize? getItemVisibleSize(int index) {
assert(_debugAssertBinded());
return _interface!.getItemVisibleSize(index);
}