A Deep Dive Into ViewPager
- 1. Copyright © 2013 CommonsWare, LLC A Deep Dive Into ViewPager AnDevCon Boston 2013
- 2. Copyright © 2013 CommonsWare, LLC Getting Horizontal ● Classic Android UX – Focused on vertical scrolling in conventional apps ● Now Presenting: Matias Duarte – Hired by Google away from Palm/WebOS – Re-emphasized horizontal swiping as a pattern for moving between peer content
- 3. Copyright © 2013 CommonsWare, LLC Enter the Protagonist, Stage Left ● ViewPager: Leading Horizontal Swipe Solution – Ships with Android Support package ● Not a backport! – Works a Bit Like a ListView ● You supply an adapter, which supplies “pages” ● ViewPager shows current page ● User horizontal swipes to move back and forth between pages
- 4. Copyright © 2013 CommonsWare, LLC TheViewPager Recipe ● Add a ViewPager to your activity layout ● Create a PagerAdapter – Typical: FragmentPagerAdapter or FragmentStatePagerAdapter – Extend, override getCount() and getItem() ● Attach the PagerAdapter to the ViewPager via setAdapter()
- 5. Copyright © 2013 CommonsWare, LLC Where We At? ● Indicators: PagerTitleStrip, PagerTabStrip – Supplied with Android Support package – Add as child ofViewPager – Set android:layout_gravity to be top
- 6. Copyright © 2013 CommonsWare, LLC Where We At: Wharton Style ● ViewPagerIndicator – Library of indicators – Add as siblings ofViewPager ● E.g., stacked in vertical LinearLayout – Connect toViewPager in Java code
- 7. Copyright © 2013 CommonsWare, LLC ViewPager: Not Perfect ● Cannot Easily Be Used In a Fragment – Nested fragments possible but a bit tricky – Requires Android 4.2 or Android Support package ● MinimumThree Pages Loaded – Make sure your pages are fast to be created – More likely to be trouble since larger than ListView rows or other AdapterView scenarios
- 8. Copyright © 2013 CommonsWare, LLC Lights Bar! Camera Bar! Action Bar! ● Fragment Pages and the Action Bar – Standard Fragment/Action Bar Recipe ● setHasOptionsMenu(true) ● onCreateOptionsMenu() ● onOptionsItemSelected() – As pages are swiped, action bar items are added/removed
- 9. Copyright © 2013 CommonsWare, LLC It's Scrolling, AllThe Way Down ● Handling Scrollable Page Content – SubclassViewPager – Override canScroll() ● Return true if the designated content could be scrolled, false otherwise ● Touch point and scroll delta supplied, in case you need it (e.g., bezel swiping)
- 10. Copyright © 2013 CommonsWare, LLC N-Up Printing (Without the Printing Part) ● Showing Multiple Pages at Once – Implement getPageWidth() on your PagerAdapter ● Returns float indicating amount of pager space to devote to this page (e.g., 0.5f) – May wish to call setOffscreenPageLimit() onViewPager to raise number of cached pages
- 11. Copyright © 2013 CommonsWare, LLC Plume: A Column of Smoke ● Pages on Phones, Columns onTablets – Devise proper layouts for the screen sizes – If you have aViewPager, give it the adapter – If you do not have aViewPager: ● Use static fragments, or ● Use the adapter to give you fragments for slots – Limitation: same basic structure in all configurations (cannot deal with change)
- 12. Copyright © 2013 CommonsWare, LLC I Can Haz Better Adapter? ● FragmentPagerAdapter and FragmentStatePagerAdapter are nice but not perfect ● Limitations – UsingViewPager in some configurations, but not all – Adding/removing/reordering pages
- 13. Copyright © 2013 CommonsWare, LLC Speaker Contact Information Source Code