Talk from VoxxedDays at Vilnus where i mainly focuced on performance tips.

1. How to create great apps
or shortest way from Java Developer to
Mobile Developer

2. Yonatan Levin

3. > 10M users
Ruby,
Golang,
Python,
Android, iOS
40 cities

4. > 600
members
Google
Supported
Meetups,
Hackathons
StudyJam

5. My story
back in 2011

6. Me
- Working in Telecom company. Writing
awful C-like language and SQL queries.
- Dream big

8. Over 20K fans
40k Installs
19k messages
over 1k photos
1 failure (not really)

9. Android what?

10. 1.3Bn Smartphones shipped
64% of traffic comes from mobile

11. - No subscription fee
- I had a Samsung S2 phone
Go Android!
I’m the engineer.

12. Smartphone - Nexus 6

13. Tablet - Nexus 9

14. Android Wear

15. Android TV

16. Android Auto

17. Where do i learn this?

18. Mobile Cloud Computing
with Android
Android Developer Nanodegree

19. Cool, i learned it.
Now i need to design my
app

20. 3 Main Things
- Who is your user
- Where he use it
- When he use
Don’t be selfish, be part of ecosystem

21. One design to rule them all
- Design for multiple screens first
- Same user experience across all device
- Don’t be afraid to
change

22. GAPPS - gmail, calendar,
google maps etc...
http://www.pttrns.com/
http://androidniceties.tumblr.com/
https://developer.android.com/design/patterns/index.html
https://developer.android.com/design/material/index.html
Follow the path, Luke

23. Sketch it

24. For tablets too

25. Nice, i have a design.
What next?

30. So i created the app
and released it

31. And then it’s crashed

33. Performance Issues

35. 84% of users find app store ratings important when considering
whether or not to download an app

36. Save my battery
9% == 1,5h Battery life

37. Permissions. What?!?!?!? k

38. Don't do work that you don't
need to do.
Don't allocate memory if you can
avoid it.

39. OutOfMemory - Bitmap memory usage
Image 1080X1920pixels, 124KB .png compressed
Bitmap size = Width * Height * depth(4 bytes) = 8 MB!!!!
Reduce the size before loading it to the memory.

41. OutOfMemory - Garbage collector
A large number of small allocations can also cause heap
fragmentation
10,000 references waiting to be collected by GC

42. OutOfMemory - Garbage collector
“To improve is to change; to be perfect is to change often.” – Winston Churchill

43. OutOfMemory - Garbage collector
Reuse of the same object
No short term temporary object for String

44. Why i’m so care about
memory?

45. 60 FPS

46. Memory overhead - Autoboxing
Object with just one int take 16 bytes at minimum
Object overhead (8 bytes ) + Overhead of dlmalloc(8 bytes) + data (n
bytes) = >16 bytes

47. Primitive Type vs Object
Integer (16 bytes) vs int(4 bytes)
Boolean(16 bytes) vs boolean(4 bytes)
or
bit-field(1 bit) //even better!

48. Enums vs Ints
Very simple - don’t use Enums
== + 1,112 bytes

49. Enums vs Ints
Final static variable + annotations = 128 bytes

50. Memory Leak

51. - Release memory when your activity no longer visible
- Don’t hold direct references. Use WeakReference
- Use inner static classes
- Stop all your handlers, threads in onStop callback
Memory Leak

53. Serialization
Flatbuffers

54. Serialization/Deserialization
Serialization Deserializati
on

55. Serialization/Deserialization
Advantage - It’s human readable. And it’s biggest weak point.
Memory overhead

56. - Faster
- Lighter

57. Last words...
“An amazing journey starts outside of your comfort zone” - Liat Aaronson
2013 - Establishing Android Academy
2014 - Closing startup and joining Gett
2015 - Helping and Lecturing over the world

58. levinyon@gmail.com
https://plus.google.com/+YonatanLevin