This document summarizes key topics from Udacity Lesson #3 on activities and intents in Android development. It covers listeners, toasts, navigation up vs back, implicit and explicit intents, fragments, shared preferences, and broadcast receivers. For each topic, it provides an overview and sometimes notes potential issues or solutions.

1. Lecture #3
Activities && Intents

2. General Stuff
- Facebook Group
- Udacity Lesson #3
- Study Jam Group Signup
- My ActionBar looks different
- 23/2 No lesson

3. Udacity Lesson Overview
- Listeners
- Toast
- UP Navigation vs Back Navigation(TASK)
- StartActivity
- Intent (bundle) Implicitly & Explicitly
- Fragment
- Settings
- SharedPreferences
- BroadCast Receivers

4. Toast

5. Context
- Global information about an application
environment
- Loading resources, launching a new
Activity, obtaining a system service,
getting internal file paths, and creating
views
- Biggest memory leak potential (latter in
our sessions)

6. Listeners
Interface related to view with
single callback.
Will be called when event is
occur

7. Event Listeners
onClick() - View.OnClickListener
onLongClick() - View.OnLongClickListener
onFocusChange() -
View.OnFocusChangeListener
onKey() - View.OnKeyListener
onTouch() - View.OnTouchListener
onCreateContextMenu() - View guess what :)

9. But?
- Hard to maintain
- Hard to find which button do what
- Every class in Java, including anonymous
inner classes which create an object and
writes accessor methods internally, uses
about 500 bytes of code.

11. Navigation UP and Back
- Task and Backstack
- Back navigation is within Task
- UP is hierarchical navigation

12. Intent
- Has address
- Has data map: key = value
- Has schema
You can pass any primitive types and also
serializable/Parcelable objects
Used to send data/action across the system

13. StartActivity
Explicitly:
Implicitly:

14. But what if?

15. But what if?

16. But what if?
- Non readable
- Mix of static variables
- Other activities should know what target
expect

17. Solution

18. Solution

19. Fragment
The biggest advantage
and pain
- .commit() asynchronous
- any operation after state of Activity was
saved
- Getting “Context” within Fragment

20. Solution
- Use callbacks when possible.
- Manage internal state of activity and
fragment
- DialogFragment special treatment

21. SharedPreferences
- Great thing to store persistent various.
- Not accessible by other apps
- Used to save things between session
and session
- Sometimes could be great
communication tool (like intent) using
“onSharedPreferenceChangeListener”

23. But...
- Don’t forget that each commit() is IO
operation.
- use Apply() instead

24. Broadcast Receivers
Great guy :)
- Loose Coupling
- 1-to-n relationship
- The onReceive() method is always executed on the
main thread
- You can notify components in your entire application, so
the communicating components do not have to "see"
each other.

25. But...
- Marshaling data via intent really hard
- Register/Unregister it when you do not needed him
(BaseActivity)
- Not impossible to transfer large objects