from the AnDevCon Boston 2013 conference

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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

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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

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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()

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Where We At?
● Indicators: PagerTitleStrip, PagerTabStrip
– Supplied with Android Support package
– Add as child ofViewPager
– Set android:layout_gravity to be top

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Where We At: Wharton Style
● ViewPagerIndicator
– Library of indicators
– Add as siblings ofViewPager
● E.g., stacked in vertical LinearLayout
– Connect toViewPager in Java code

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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

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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

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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)

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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

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