What is View Pager ?
ViewPager is the widget that allows the user to swipe left or right to see an entirely new screen.
ViewPager has the ability to dynamically add and remove pages (or tabs) at anytime.
ViewPager are user could then swipe left or right to see other categorized lists. Using the ViewPager requires some knowledge of both Fragments and PageAdapters.
Pager Adapter
Android ViewPager is a layout manager that allows the user to flip left and right through pages of data. You supply an implementation of a PagerAdapter to generate the pages that the view shows.
The PagerAdapter providing the adapter to populate pages inside of a ViewPager.
It does not Required Fragment only use on xml layout file to attach in view pager.
It is limited (fixed) number of items (Fragments).
it never removes a fragment instance from FragmentManager.
When you implement a PagerAdapter, you must override the following methods at minimum:
instantiateItem(ViewGroup, int)
destroyItem(ViewGroup, int, Object)
getCount()
isViewFromObject(View, Object)
FragmentStatePagerAdapter
It is Required and implementation Fragments.
A FragmentStatePagerAdapter is more memory savvy.
It completely removes Fragment instances from the FragmentManager once they are out of reach.
The state of the removed Fragments is stored inside the FragmentStatePagerAdapter.
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