http://developerstudyjams.com/ Week 5 - Retrospectively looking at Udacity Lesson 4 Activity Lifecycle & Databases Google Developers Study Jams is a free series of global, community-run, in-person study groups. The first Study Jams series is presented in partnership with Udacity and will follow their Android Fundamentals curriculum. Google Developer Group facilitators certified in the course will lead the Study Jams that meet once weekly for 8 - 9 weeks. Promote using hashtag #devstudyjam

1. Android Manchester
Week 4 - Activity Lifecycle & Databases

2. Overview
● Retro
o Lesson 4a Activity Lifecycle & Databases basics
● Looking forward
o Lesson 4b ContentProviders
o Lesson 4c Loaders?
● Stickers + Booklets
● Next Tue 7-8pm SpacePortX

3. Energizer
Stand up and introduce yourself to
somebody around you, you don’t know

4. Prime Directive
‘Regardless of where we are up to, we
understand and truly believe that
everyone did the best job he or she
could, given his or her skills and
abilities, the personal time available,
and the situation at hand.’

5. Difficulty Check
● Who completed the class?
● How long did it take?
● Hands up 1-10 difficulty of the weeks lesson
● Any specific areas of the lesson that require particular
focus?

6. Retro Activity Lifecycle & Databases
What we learnt last week
● Why the Activity Lifecycle is important
● The Activity Lifecycle
● Data persistence methods in Android
● SQLite
● ContentProvider
● Testing basics

7. Lesson 4a - Activity Lifecycle
● Why we need to know the Activity LifeCycle?
o Interruptions
o Memory issues
o Saving state
o User exits app
● Activity LifeCycle Methods come in pairs
o onDestroy - ?
o onStart- ?
o onResume - ?
● How often are the following methods called
o onResume?
o onStart?
o onCreate?

8. Lesson 4a - Answers
● Activity LifeCycle Methods come in pairs
o onDestroy() - onCreate
o onStart() - onStop
o onResume() - onPause
● How often are the following methods called
o onResume - multiple time
o onStart - multiple time
o onCreate/onDestroy - once
o onSavedInstanceState, onRestoreInstanceState

9. Lesson 4a - Lifecycle of an Activity

10. Lesson 4a - Termination of activity in
onStop()
or
onPause()
pre-honeycomb

11. Lesson 4a - Activity LifeCycle
● Save state in onPause
or in onSavedInstanceState
● Restore in onCreate
or in onRestoreInstanceState

12. Activity Lifecycle Visibility
Difference between onStop/onStart & onPause/onResume
is visibility
● onPause for overlays
● onStop for background

13. UX of the exit button
- Android doesn’t have a concept of exit
- What does exit even mean
https://www.youtube.com/watch?v=631T7B8HOv4

14. Lesson 4a: Databases
● SharedPreferences Key-Value pairs for primitives -
covered last week
o Don’t work with complex data
o Can’t query
● Databases
o SQLite
 Easier to Query, Update, Delete

15. Lesson 4a: Why Save Data
● Just fetch it from the cloud every time?
● Responsive (fast) application
● Responsible (sensible) application

16. Lesson 4a: Why Databases
● Efficient to find things
● Easy to organise
● Indexing
● Tables
VS

17. Lesson 4: Databases Overview
Three main components in the data storage methodology for this course
Contract
DbHelper
ContentProvider

18. Lesson 4a: Databases Helper
● Most important class
o Extends SQLiteOpenHelper
● onCreate()
o creates the tables using SQL query
o Called only the first time database is created.
● onUpgrade
o If the database updated you can call “Alter Table” SQL here to
ensure data is not lost during transition
● Other methods of note
o onDowngrade, getDatabaseName, getWriteableDatabase or
getReadableDatabase, onOpen, close.

19. Lesson 4a: Contract
● Define Table names & columns
o Also define URI helper methods
 More on this next week.
● DbHelper will become unreadable if you had Col names, types, util
methods in an encompassing class.
● ContentProviders
o Hook to access database from anywhere
in the app in a safe manner
 More next week!

20. Lesson 4a: Testing
● Convenient way of ensuring database is valid
o deals with edge cases
o Gives devs confidence in data validity
● TestSuite subclass specifies which tests to run
● AndroidTestCase subclass specifies x tests
● Test methods are prefixed with “test”
o i.e. testLocationInput

21. What went well

22. What went well
● Understanding the android lifecycle
● Restoring state
● Contract pattern in DB’s/ContentProvider
● Public Contracts (knowing what to do)
o http://developer.android.com/reference/android/provider/ContactsContract.html
● Code written for you
● Testing
o Saved a lot of time & pain

23. What didn’t go so well

24. What didn’t go so well
● Optional SQLite tutorial to read
● Code written for you
● Threading issues with the database
● Upfront talk of foreign keys & joins
o didn’t understand why until much later
● Testing
o caused a lot of time and pain

25. Q&A

26. Next Week - Android Jam
ContentProviders

27. Next Lesson - Content Providers
Learning Objectives:
- Creating a content providers
- URI, Uri Matcher, Uri Builder
- Bulk inserts
- Efficient updates.

28. See you next week..
- Time: Tuesday 7pm
- Place: SpacePort
- Things needed: You + Questions +
Feedback
- Can contact us if issues:
@blundell_apps / @android_mcr

29. Go forth and discuss