As presented during droidcon.de 2015 As an Android developers we use various frameworks and libraries provided by Google and others. Sometimes they are just a pure magic (say hi to Jake Wharton and his ActionBarShelock!) and sometimes… Well, if we make an effort to grap the source code and go through it, we realise there is no magic there. During my presentation, I will go deep into Lollipop’s new JobScheduler API. See what’s really there, how it’s advertised, and try to assess how big is the gap between us and guys at Google. Should we have any inferiority complex or could we write this code ourselves?

1. Android Lollipop Internals
and our inferiority complex
or impostor syndrome

2. +AleksanderPiotrowski
@pelotasplus

3. About presentation
and the gap between us mortals
and rockstar developers from
Square and Google

4. History
● originally as “What’s new in Lollipop”
● about new APIs
● how it works under the hood
● the devil is in the detail
http://nelenkov.blogspot.de/@kapitanpetko

5. What to look for
● technical information
a bit
● motivation
hopefully lot more
● are we rockstar devs
or not?

6. Disclaimer

7. Disclaimer
● nothing against the Google
● actually make a living thanks to their
technologies

8. Disclaimer
● don’t want to diminish their achievements
● or suggest anything bad about their devs

9. Disclaimer
● have never been recruited by them

10. The APIs arms race

12. The APIs arms race
● each new release thousands new APIs
● iOS 8 includes over 4,000 new APIs
● thousands of new Material Designs or new
Bluetooth stacks?

13. The APIs arms race
● the more, the better
● … or just a marketing?
● Android Weekly pressure ;-)

14. Lollipop
Or any other Android version, I guess

15. Significant changes
● Material Design
● WebView updated via Play Store
● FDE

16. Significant changes
● Bluetooth stack changes
● Android Work/Multi-user - BYOD
● JobScheduler API

19. One random change
● new package android.util.Range
● immutable range

20. android.util.Range
● check if a value is in a range
● check if ranges are equal
● get lower/upper values
● intersect two ranges

21. Range::contains(value)
public boolean contains(T value) {
checkNotNull(value, "value must not be null");
boolean gteLower = value.compareTo(mLower) >= 0;
boolean lteUpper = value.compareTo(mUpper) <= 0;
return gteLower && lteUpper;
}

22. The Projects

23. Project Butter
● in JellyBean
● smoother UI
60fps

24. Other projects
● Svelte in KitKat
running low-end on devices
with 512MB or less
● Pi ;-)
Google as a telecom

25. Project Volta
● improve battery life

26. Project Volta
● at platform level
● at developers level
● at users level

27. Project Volta
● ART runtime
● JobScheduler API and Battery Historian
● Battery Saver

28. JobScheduler API

29. Our task
Our App
Task
● non user-facing
background task ;-)
● can wait to be run later
execution time doesn’t
matter
● resource intensive

30. The old way
Our App
Task
Alarm
Manager
Network
Manager
Battery
Manager

31. JobInfo.Builder builder =
new JobInfo.Builder(jobId, serviceComponent)
.setMinimumLatency(4000)
.setOverrideDeadline(5000)
.setRequiredNetworkType(
JobInfo.NETWORK_TYPE_UNMETERED)
.setRequiresCharging(true)
.setPersisted(true);
JobInfo jobInfo = builder.build();
constraints
our task
task is now a job

32. JobScheduler
Our App Job
Info
JobInfo.Builder

33. JobScheduler
Our App Job
Info
JobInfo.Builder schedule()
Job
Scheduler

34. Job
Scheduler
System
Service

35. Job
Scheduler
System
Service
Battery
Service
android.content.Intent#ACTION_BATTERY_CHANGED

36. Job
Scheduler
System
Service
Battery
Service
android.content.Intent#ACTION_BATTERY_CHANGED
WebView
Update
Service
android.content.Intent
#ACTION_PACKAGE_REPLACED

37. JobScheduler
Job
Scheduler
Job
Info

38. JobScheduler
Job
Scheduler
#1
Job
Info
#2
Job
Info
#3
Job
Info
/data/system/job/jobs.xml

39. JobScheduler
Job
Scheduler
#1
Job
Info
#2
Job
Info
#3
Job
Info
/data/system/job/jobs.xml
Battery TimeNetwork ***

40. BatteryController
public class ChargingTracker extends BroadcastReceiver {
private final AlarmManager mAlarm;
private final PendingIntent mStableChargingTriggerIntent;
[...]
@Override
public void onReceive(Context context, Intent intent) {
onReceiveInternal(intent);
}
}

41. public void startTracking() {
IntentFilter filter = new IntentFilter();
// Battery health.
filter.addAction(Intent.ACTION_BATTERY_LOW);
filter.addAction(Intent.ACTION_BATTERY_OKAY);
// Charging/not charging.
filter.addAction(Intent.ACTION_POWER_CONNECTED);
filter.addAction(Intent.ACTION_POWER_DISCONNECTED);
// Charging stable.
filter.addAction(ACTION_CHARGING_STABLE);
mContext.registerReceiver(this, filter);
[...]
}

42. public void onReceiveInternal(Intent intent) {
final String action = intent.getAction();
if (Intent.ACTION_BATTERY_LOW.equals(action)) {
[...]
mBatteryHealthy = false;
} else if (Intent.ACTION_BATTERY_OKAY.equals(action)) {
[...]
mBatteryHealthy = true;
maybeReportNewChargingState();
}
[...]
}

43. JobSchedulerCompat

44. JobScheduler
Facebook
Google+
Ebay
Job
Scheduler
Service
System Service
Job
Battery
Time
Network
***
Job
Info
Job
Info
Job
Info

45. JobSchedulerCompat
Facebook
Google+
Ebay
Battery
Time
Network
***
Job
Info
Job
Info
Job
Scheduler
Service
Job
Scheduler
Service
Job
Scheduler
Service
Job
Info Battery
Time
Network
***
System Service

46. GCMNetworkManager
Fresh from Google I/O 2015
Cloud Messaging 3.0

47. GCMNetworkManager
setRequiresCharging
setRequiresIdle
setRequiredNetwork
setPersisted
setRequiresCharging
setRequiresDeviceIdle
setRequiredNetworkType
setPersisted

48. ● based on GPS not API 21
so portable
● tasks vs jobs
so similar API
● jobs executed on a service
so similar API again ;-)
GCMNetworkManager

49. The Idle mode
***

51. https://www.youtube.com/watch?v=KzSKIpJepUw

52. Idle mode
system has determined
that phone is not being used
and is not likely to be used
anytime soon

53. Idle mode example
Job criteria:
idle state + charging
When:
at night, when the phone is next to your bed

54. Digression #1
Many Googles

55. Many Googles
● not the same Google for every one of us
● different search results
● different ads
● fine-grained targeting of contents

59. Almost there...
● strong technology marketing
videos, blog posts, APIs arms race
● bold statements about possibilities
idle state, at night, next to the bed
● proven track record
search and ads tailored to our behaviour

60. The idle state algorithm
or is it “idle”?

61. // Policy: we decide that we're "idle" if the device has been unused
/
// screen off or dreaming for at least this long
private static final long INACTIVITY_IDLE_THRESHOLD = 71 * 60 * 1000;
// millis; 71 min
private static final long IDLE_WINDOW_SLOP = 5 * 60 * 1000;
// 5 minute window, to be nice
quotes are here ;-)

62. The “idle” state algorithm
1. display turns off
2. start the timer for 71 minutes +/- 5 minutes
3. alarm goes off
4. if screen still turned off
we are in the idle state

63. @Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
[...]
} else if (action.equals(Intent.ACTION_SCREEN_OFF)
|| action.equals(Intent.ACTION_DREAMING_STARTED)) {
final long nowElapsed = SystemClock.elapsedRealtime();
final long when = nowElapsed + INACTIVITY_IDLE_THRESHOLD;
mAlarm.setWindow(AlarmManager.ELAPSED_REALTIME_WAKEUP,
when, IDLE_WINDOW_SLOP, mIdleTriggerIntent);
}
[...]

64. @Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
if (action.equals(Intent.ACTION_SCREEN_ON)
|| action.equals(Intent.ACTION_DREAMING_STOPPED)) {
// possible transition to not-idle
if (mIdle) {
[...]
mAlarm.cancel(mIdleTriggerIntent);
mIdle = false;
reportNewIdleState(mIdle);
}
[...]

65. @Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
[...]
} else if (action.equals(ACTION_TRIGGER_IDLE)) {
// idle time starts now
if (!mIdle) {
[...]
mIdle = true;
reportNewIdleState(mIdle);
}
}
}

66. The “idle” state algorithm
● time is not a factor
at night
● sensors not used
lying next to the bed
Android Doze to the rescue?

67. The “idle” state algorithm
● display the only factor
how long is being turned off
● not tuned per user
same for everyone
not based on our own behaviour

68. The “idle” state algorithm
● random 71 minutes
or maybe there is some magic here?

69. Takeaways
● don’t be afraid to look at the code
not a rocket science there
can cure from inferiority complex
● write code to get better
it always sucks with the first version
gets better which each commit or PR

70. Thanks
● droidcon Berlin
● YOU
for attending my talk
and others too ;-)

71. +AleksanderPiotrowski
@pelotasplus