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from AnDevCon SF 2013, the October 2013 Skills Matter "In the Brain" session, and the Android Alliance Philadelphia October 2013 meetup
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Copyright © 2013 CommonsWare, LLC
Mastering the Master/Detail
Pattern
AnDevCon SF 2013
Copyright © 2013 CommonsWare, LLC
Who Made You the Master?
● Master/Detail Pattern– Master = a collection of content
● Title/display name● Other metadata
– Detail = specifics about one piece of content● Pattern
– Show master or detail on smaller screens– Show master and detail on larger screens
Copyright © 2013 CommonsWare, LLC
Who Made You the Master?
Image courtesy of Google and AOSP
Copyright © 2013 CommonsWare, LLC
Stamping Out a Template
● Master/Detail Flow App Template– Option in Eclipse when creating a new project– Results
● Two activities (master/detail and detail-only)● Two fragments (master and detail)● Four layouts (plus a layout alias)● Always single-pane or dual-pane, based on screen
size
Copyright © 2013 CommonsWare, LLC
Nuking an Activity
● One Activity/Two Fragments– In single-pane mode, Activity executes a
FragmentTransaction to replace list with detail● Adds to back stack to allow BACK to reverse the
transaction and return to master
– In dual-pane mode, just shows both fragments
Copyright © 2013 CommonsWare, LLC
Nuking an Activity
● Pros– One less activity (class, manifest, etc.)– Not limited by Intent extras
Copyright © 2013 CommonsWare, LLC
Nuking an Activity
● Cons: Too Many Scenarios– Do we have a master fragment in the FragmentManager?
● If yes, is it visible? Should it be?– Do we have a detail fragment in the FragmentManager?
● If yes, is it visible? Should it be?– What happens when the user presses BACK?
– What happens if we rotate the screen and change strategies?
Copyright © 2013 CommonsWare, LLC
Slip Sliding Away
● SlidingPaneLayout– Android Support package– Handles complexity for you
● Single-pane vs. dual-pane● Swipe gesture to show, hide master in single-pane
mode● All the configuration change idiosyncrasies
Copyright © 2013 CommonsWare, LLC
Slip Sliding Away
● SlidingPaneLayout Pros– Simplicity
● SlidingPaneLayout Cons– Confusion over swipe gesture– Detail-first single-pane flow
● Can be fixed, requires a bit of extra code
Copyright © 2013 CommonsWare, LLC
Yet More Horizontal Swiping
● ViewPager– ViewGroup, attached to a PagerAdapter
● FragmentPagerAdapter, FragmentStatePagerAdapter, or custom implementation
– Horizontal swipes move between pages– Optional “indicators” to show where the user is
in the sea of pages
Copyright © 2013 CommonsWare, LLC
Yet More Horizontal Swiping
● ViewPager and Design– “On a phone, since the master and detail are on
separate screens, this typically requires the user to jump back and forth between the list and the detail view, aka "pogo-sticking".”
– “In cases where users will want to view multiple detail items in succession, avoid pogo-sticking by using the swipe gesture to navigate to the next/previous detail view.”
Copyright © 2013 CommonsWare, LLC
Yet More Horizontal Swiping
Copyright © 2013 CommonsWare, LLC
Yet More Horizontal Swiping
● ViewPager in Master/Detail– Single-Pane: Consider ViewPager for Detail
● Swipe between peer details● BACK to return to master● Ideal: context provided by content, so no tabs, etc.
– Dual-Pane: Probably Not Necessary● Can randomly access any detail via master pane, so
swiping not necessary
Copyright © 2013 CommonsWare, LLC
Yet More Horizontal Swiping
● ViewPager Challenges– Switching Between Single-Pane/Dual-Pane
● Fragment*PagerAdapter is very “grabby”, does not like others messing with its contents
● Net: need another PagerAdapter implementation
– Yet More Collisions with Horizontal Swipe Gestures
● Probably need to skip SlidingPaneLayout
Copyright © 2013 CommonsWare, LLC
Lights Mode! Camera Mode! Action Mode!
● Action Modes– A.k.a., contextual action bar– Replaces regular action bar for contextual
actions● When 1+ selected for such actions● Can perform actions upon group of selected items,
such as “delete” or “move”
– Dismissed via Done or BACK
Copyright © 2013 CommonsWare, LLC
Lights Mode! Camera Mode! Action Mode!
● Action Modes and Design– Replacement for old-style context menu– Trigger Options
● Always-available checklist● Long-press to select first, moves into a multi-select
mode
Copyright © 2013 CommonsWare, LLC
Lights Mode! Camera Mode! Action Mode!
● Action Modes and Master/Detail– Master should support action modes
● Exception: no relevant actions (unlikely)● Read-only vs. read-write actions● Emphasis on multiple-selection scenario
– Detail should support actions● Single-pane: action bar● Dual-pane: action bar and action mode
Copyright © 2013 CommonsWare, LLC
Lights Mode! Camera Mode! Action Mode!
● Action Mode Challenges– Multiple Flavors of Master List Highlighting
● Single-pane: regular or multiple-selection● Dual-pane: activated or multiple-selection
– Detail in Multiple-Selection?● First detail? Last detail? Empty? Special content?
– Retaining Action Mode and Selections● Configuration changes, etc.
Copyright © 2013 CommonsWare, LLC
But Wait! There's More!
● Presentation– What do we do when there is a secondary
screen?● Splitter
– Should we allow resizing of panes in dual-pane mode?
Copyright © 2013 CommonsWare, LLC
But Wait! There's More!
● Action Bar Items– Need to ensure change properly
● Moving between master, detail in single-pane mode● Reasonable blend of both in dual-pane mode
● Navigation Drawer– Yet more conflict with horizontal gestures– Fallacy of the “bezel swipe”
Copyright © 2013 CommonsWare, LLC
Copyright © 2013 CommonsWare, LLC
CWAC-MasterDetail
● Canned “best practices” in reusable form● Objectives
– Maximum adherence to design guidelines– Minimum additional code to plug in your content
Copyright © 2013 CommonsWare, LLC
CWAC-MasterDetail
● Library Usage– Subclass MasterDetailActivity– Override buildMasterDetailHelper(),
returning instance of own subclass of MasterDetailHelper
– Override buildPagerAdapter() and buildModelCollection() in MasterDetailHelper
– Beer!
Copyright © 2013 CommonsWare, LLC
CWAC-MasterDetail
● Library Functionality, Today– Automatic handling of configuration changes– ViewPager in single-pane mode– Splitter support– Custom empty views (list, detail) and
multiple-choice view (detail)– Optional action mode support– Optional custom master contents
Copyright © 2013 CommonsWare, LLC
CWAC-MasterDetail
● Library Functionality, Future– Undo bar– Display vs. edit modes for detail– Presentation support– Filtering support– Ordered list support– And more!
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