When should getItemPosition consider changes of an item's position?

Question

The documentation for the method getItemPosition in Android\'s PagerAdapter class states that it is:

Called when the host view is attempting to determine

Answer 1

You can see in ViewPager.java that getItemPosition is called only in dataSetChanged. This means the item's position changed if it's different than the last time dataSetChanged was called.

I would not worry so much about the meaning of "changed"; there are two cases:

1. The position of the added items never changes, then getItemPosition returns POSITION_UNCHANGED;
2. The position of the items changes, or items are removed. If the item position did not change, there is no difference if you return POSITION_UNCHANGED or the actual position. So to keep the implementation simple you can return the position (or POSITION_NONE) and forget about POSITION_UNCHANGED..