Android Lollipop Internals and our inferiority complex 

Presentation from droidcon Zagreb 2015
While going through JobScheduler internals try to answer the following question: How big is the gap between us and rockstar developers from Google or Square

1. Android Lollipop Internals and our inferiority complex
2. +AleksanderPiotrowski @pelotasplus
3. About presentation
4. Inferiority complex • mine but maybe yours as well? • gets better with each PR or a talk • … or look taken at others code
5. History • originally as “What’s new in Lollipop” • about new APIs • how it works under the hood • the devil is in the detail
6. What to look for • technical information - a bit • motivation - hopefully lot more
7. Disclaimer
8. Disclaimer • nothing against the Google • actually make a living thanks to their technologies
9. Disclaimer • don’t want to diminish their achievements • or suggest anything bad about their devs
10. Disclaimer • have never been recruited by them
11. The APIs arms race
13. 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?
14. The APIs arms race • the more, the better • … or just a marketing? • Android Weekly pressure ;-)
15. Lollipop
16. Significant changes • Material Design • WebView updated via Play Store • FDE
17. Significant changes • Bluetooth stack changes • Android Work/Multi-user - BYOD • JobScheduler API
20. One random change • new package android.util.Range • immutable range
21. android.util.Range • check if a value is in a range • check if ranges are equal • get lower/upper values • intersect two ranges
22. 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; }
23. The Projects
24. Project Butter • in JellyBean • smoother UI 60fps
25. Other projects • Svelte in KitKat running low-end on devices with 512MB or less • Pi ;-) Google as a telecom
26. Project Volta • improve battery life
27. Project Volta • at platform level • at developers level • at users level
28. Project Volta • ART runtime • JobScheduler API and Battery Historian • Battery Saver
29. JobScheduler API
30. JobScheduler Our App Task
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 Time Network ***
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. BatteryController 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. BatteryController public void onReceiveInternal(Intent intent) { final String action = intent.getAction(); if (Intent.ACTION_BATTERY_LOW.equals(action)) { [...] // If we get this action, the battery is discharging => it isn't plugged in so // there's no work to cancel. We track this variable for the case where it is // charging, but hasn't been for long enough to be healthy. 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. The Idle mode ***
48. https://www.youtube.com/watch?v=KzSKIpJepUw
49. Idle mode system has determined that phone is not being used and is not likely to be used anytime soon
50. Idle mode example Job criteria: idle state + charging When: at night, when the phone is next to your bed
51. Digression #1 Many Googles
52. Many Googles • not the same Google for every one of us • different search results • different ads • fine-grained targeting of contents
56. 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
57. The idle state algorithm or is it “idle”?
58. // 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 ;-)
59. 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
60. @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); } [...]
61. @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)) { // when the screen goes off or dreaming starts, we schedule the // alarm that will tell us when we have decided the device is // truly idle. final long nowElapsed = SystemClock.elapsedRealtime(); final long when = nowElapsed + INACTIVITY_IDLE_THRESHOLD; if (DEBUG) { Slog.v(TAG, "Scheduling idle : " + action + " now:" + nowElapsed + " when=" + when); } mAlarm.setWindow(AlarmManager.ELAPSED_REALTIME_WAKEUP, when, IDLE_WINDOW_SLOP, mIdleTriggerIntent); } [...]
62. @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) { if (DEBUG) { Slog.v(TAG, "Idle trigger fired @ " + SystemClock.elapsedRealtime()); } mIdle = true; reportNewIdleState(mIdle); } } }
63. The “idle” state algorithm • time is not a factor at night • sensors not used lying next to the bed
64. 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
65. The “idle” state algorithm • random 71 minutes or maybe there is some magic here?
66. 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
67. Thanks • droidcon Zagreb • YOU <3 for attending my talk and others too ;-)