Ronan Schwarz, OpenIntents In this talk, we will once again walk through the Android Application fundamentals - but this time from the Framework's point of View. - You will learn why there is, in fact, no app - only a bunch of Activities. - What a HistoryRecord is, what it is used for and it's implications for the lifecycle. - Why ContentProviders are a type of service. - How the Framework enforces Permissions across the system and what to make of it. - Why Intents are even way better for RPC calls then is seen at first sight. We will cover a lot of little tricks and some bigger parts of the Android framework and it's implementation, giving you new insights for everyday development

1. OpenIntents
www.OpenIntents.org
ANDROID
FUNDAMENTALS
REVISITED
@_zero
zero@openintents.biz

2. OpenIntents OpenIntents
www.OpenIntents.org
● Founded in 2009
● Open Source based Company
● Two times winners of Google Android Developer Challenge
● Over 15 Apps in the Market (Free + Paid )
● Services:
● Reusable components
● Intents Registry
● Developer Support
● Consulting
● App Development
●
Mentoring organization in Summer of Code 2011

4. OpenIntents
www.OpenIntents.org Topics
● Activity Lifecycle
● Activity Manager
● Concepts
● Components
● Why there is no App
● Permissions
● Gingerbread

7. OpenIntents
www.OpenIntents.org Who you're gonna call ?

8. OpenIntents
www.OpenIntents.org Activities
ActivityManagerService

9. OpenIntents
www.OpenIntents.org ActivityManagerService
● Project: frameworks/base.git
● Package: com.android.server.am
● Pure Java
● Started by SystemServer, running as system process
● Creates the System Context
● Keeps a reference of the Home Screen / Launcher App

10. OpenIntents
www.OpenIntents.org What does ActivityManagerService do ?
● Start, stop, pause,... Activities
● Start, stop, pause,... Services
● Start, stop, pause,... ContentProviders
● Check Permission
● Broadcast Intents
● Start, stop, pause,... Animations
● Decide window focus
● Deliver Hardware Events
● Crash Activities

11. OpenIntents
www.OpenIntents.org What does ActivityManagerService do ?
EVERYTHING

12. OpenIntents
www.OpenIntents.org What does ActivityManagerService do ?
EVERYTHING
the window manager doesn't

13. OpenIntents
www.OpenIntents.org What does ActivityManagerService do ?
EVERYTHING
the window manager doesn't
(ok, almost)

14. OpenIntents
www.OpenIntents.org Starting an Activity
● startActivity is called (calls startActivity(Intent, -1)
● ActivityManagerNative.startActivity(..)
● Call gets dispatched via AIDL Binder to ActivityManagerService
● Call is queued in a Handler Message Queue
● startActivityXX is called
● startActivityLocked is called

15. OpenIntents
www.OpenIntents.org Starting an Activity
● Class is resolved
● Permission check
● Inform Watchers
● Create HistoryRecord
● Check launch Flags
● Create Task or add to existing
● Grant Permissions

16. OpenIntents
www.OpenIntents.org Starting an Activity
● Add to History Stack
● Prepare Animations
● Add to WindowManager (creates window)
● Pause currently running Activities
● Switch Visibility
● Calculate & update Configuration (may trigger reset)
● Resume (make call across Binder into Activity Thread)
● Set Focus
● Ensure visibility

17. OpenIntents
www.OpenIntents.org Application ?

18. OpenIntents
www.OpenIntents.org HistoryRecord

19. OpenIntents
www.OpenIntents.org Application ?

20. OpenIntents
www.OpenIntents.org Permissions

21. OpenIntents
www.OpenIntents.org Permissions

22. OpenIntents
www.OpenIntents.org Permissions

24. OpenIntents
www.OpenIntents.org Changes in Gingerbread
● HistoryRecord renamed to ActivityRecord
● Introduction of Heavyweight Process
● Only one at any given time
● Parts of lifecycle management moved to ActivityStack
● Hardware Event / Key input was re-written
● WindowManager now has an extra “secure” layer
● ...
● Beautified comments :)