Doing Background Tasks the Right Way

With the large variety of options that Android provides to perform background tasks, developers can get confused on the right way to do background work for their use case. In this talk, I discuss the various ways of doing background work on Android, the challenges various OS versions introduces and the most effective way to perform tasks for various specific use cases.

Transcript

1. Doing Background Tasks the Right Way Subhrajyoti Sen / @iamsubhrajyoti smallcase
2. The Main Thread
3. The Main Thread • Default thread that apps start on
4. The Main Thread • Default thread that apps start on • Known as the UI thread
5. The Main Thread • Default thread that apps start on • Known as the UI thread • Changes to android.view and android.widget need to happen to this thread
6. The Main Thread • Default thread that apps start on • Known as the UI thread • Changes to android.view and android.widget need to happen to this thread • Responsible for dispatching touch events
7. The Main Thread • Default thread that apps start on • Known as the UI thread • Changes to android.view and android.widget need to happen to this thread • Responsible for dispatching touch events • Lifecycle callbacks happen on this thread
8. The Main Thread is Precious
9. The Main Thread is Precious • Refreshed at a regular interval
10. The Main Thread is Precious • Refreshed at a regular interval • Should be never blocked
11. The Main Thread is Precious • Refreshed at a regular interval • Should be never blocked • Any operation longer than a few milliseconds should not take place on the Main Thread
12. The Main Thread is Precious • Refreshed at a regular interval • Should be never blocked • Any operation longer than a few milliseconds should not take place on the Main Thread Or else...
14. The Solution
15. The Solution Do work in the background
16. The Solution Do work in the background When the user is using the app
17. The Solution Do work in the background When the user is using the app When the user is not using the app
18. Why is background work challenging?
19. A process is not forever - Keith Smith
20. The Process Priority Table
21. The Process Priority Table 1. Native
22. The Process Priority Table 1. Native 2. System
23. The Process Priority Table 1. Native 2. System 3. Persistent Apps
24. The Process Priority Table 1. Native 2. System 3. Persistent Apps 4. Foreground Apps
25. The Process Priority Table 1. Native 2. System 3. Persistent Apps 4. Foreground Apps 5. Perceptible Apps
26. The Process Priority Table 1. Native 2. System 3. Persistent Apps 4. Foreground Apps 5. Perceptible Apps 6. Service
27. The Process Priority Table 1. Native 2. System 3. Persistent Apps 4. Foreground Apps 5. Perceptible Apps 6. Service 7. Home
28. The Process Priority Table 1. Native 2. System 3. Persistent Apps 4. Foreground Apps 5. Perceptible Apps 6. Service 7. Home 8. Previous App
29. The Process Priority Table 1. Native 2. System 3. Persistent Apps 4. Foreground Apps 5. Perceptible Apps 6. Service 7. Home 8. Previous App 9. Cached Apps
30. Solutions by Android
31. Solutions by Android AsyncTask Coroutines RxJava AlarmManager Foreground Service Loader Thread and Handler Intent Service WorkManager Job Scheduler
32. So many solutions!!!
33. BUT WHY
34. Changes Introduced in the OS
35. Changes Introduced in the OS Android 6.0 introduced Doze Source: developer.android.com
36. Changes Introduced in the OS • Android 7.0 introduced Doze on the Go
37. Changes Introduced in the OS • Android 7.0 introduced Doze on the Go • Android 8.0 introduced ◦ Background Service Limitations ◦ Broadcast Limitations
38. Changes Introduced in the OS • Android 7.0 introduced Doze on the Go • Android 8.0 introduced ◦ Background Service Limitations ◦ Broadcast Limitations • Android 9.0 introduced App Standy Buckets
39. App Standby Buckets
40. App Standby Buckets • Use machine learning to determine how likely each app will be used.
41. App Standby Buckets • Use machine learning to determine how likely each app will be used. • Places app in one of 5 priority buckets
42. App Standby Buckets • Use machine learning to determine how likely each app will be used. • Places app in one of 5 priority buckets ◦ Active ◦ Working Set ◦ Frequent ◦ Rare ◦ Never
43. The “Not Recommended” Solutions
44. AsyncTask
45. AsyncTask • Does not auto-cancel when Activity/Fragment is destroyed/recreated
46. AsyncTask • Does not auto-cancel when Activity/Fragment is destroyed/recreated • Can lead to memory leaks
47. AsyncTask • Does not auto-cancel when Activity/Fragment is destroyed/recreated • Can lead to memory leaks • Not really easy to cancel
48. AsyncTask • Does not auto-cancel when Activity/Fragment is destroyed/recreated • Can lead to memory leaks • Not really easy to cancel • Can be executed only once
49. AsyncTask • Does not auto-cancel when Activity/Fragment is destroyed/recreated • Can lead to memory leaks • Not really easy to cancel • Can be executed only once • Please do not use it
50. AsyncTask • Does not auto-cancel when Activity/Fragment is destroyed/recreated • Can lead to memory leaks • Not really easy to cancel • Can be executed only once • Please do not use it Recommended Read: The Hidden Pitfalls of AsyncTask by Dan Lew
51. Quiz 1: What feature of Android Pie did I mention that intelligently prioritizes apps?
52. Quiz 2: Name any 3 buckets from the App Standy Buckets
53. Loaders
54. Loaders • Deprecated on Android P (API 28)
55. Loaders • Deprecated on Android P (API 28) • Confusing API
56. Loaders • Deprecated on Android P (API 28) • Confusing API • Can be unpredictable
57. Loaders • Deprecated on Android P (API 28) • Confusing API • Can be unpredictable Recommended way of replacing Loaders is a combination of ViewModel and LiveData
58. The “Recommended” Solutions
59. DownloadManager
60. DownloadManager • Perform long-running HTTP downloads
61. DownloadManager • Perform long-running HTTP downloads • Handles HTTP interaction
62. DownloadManager • Perform long-running HTTP downloads • Handles HTTP interaction • Retry on failure
63. DownloadManager • Perform long-running HTTP downloads • Handles HTTP interaction • Retry on failure • Continuation after reboot
64. DownloadManager • Perform long-running HTTP downloads • Handles HTTP interaction • Retry on failure • Continuation after reboot • Handles connectivity changes
65. DownloadManager • Perform long-running HTTP downloads • Handles HTTP interaction • Retry on failure • Continuation after reboot • Handles connectivity changes • Notifies user of progress updates
66. DownloadManager • Perform long-running HTTP downloads • Handles HTTP interaction • Retry on failure • Continuation after reboot • Handles connectivity changes • Notifies user of progress updates Use case: download a PDF report
67. Quiz 3: Which API level was Loader deprecated in?
68. Quiz 4: What should you use to replace Loader?
69. Foreground Services
70. Foreground Services • High priority is the process ranking system.
71. Foreground Services • High priority is the process ranking system. • Non-dismissible notification
72. Foreground Services • High priority is the process ranking system. • Non-dismissible notification • Should be used for immediate, important tasks
73. Foreground Services • High priority is the process ranking system. • Non-dismissible notification • Should be used for immediate, important tasks • Should have well defined start and finish
74. Foreground Services • High priority is the process ranking system. • Non-dismissible notification • Should be used for immediate, important tasks • Should have well defined start and finish Use case: Playing music, high-accuracy location tracking (WhatsApp live location sharing)
75. Quiz 5: What would be the priority rank of Foreground Service in the Process Priority Table?
76. AlarmManager
77. AlarmManager • Schedule tasks at a particular time
78. AlarmManager • Schedule tasks at a particular time • Schedule tasks to execute at intervals
79. AlarmManager • Schedule tasks at a particular time • Schedule tasks to execute at intervals • Available since API 1
80. AlarmManager • Schedule tasks at a particular time • Schedule tasks to execute at intervals • Available since API 1 Gotchas:
81. AlarmManager • Schedule tasks at a particular time • Schedule tasks to execute at intervals • Available since API 1 Gotchas: • Alarms reset after phone reboot
82. AlarmManager • Schedule tasks at a particular time • Schedule tasks to execute at intervals • Available since API 1 Gotchas: • Alarms reset after phone reboot • Alarms reset is system time is changed
83. AlarmManager • Schedule tasks at a particular time • Schedule tasks to execute at intervals • Available since API 1 Gotchas: • Alarms reset after phone reboot • Alarms reset is system time is changed Use case: WhatsApp chat backup at 2AM
84. Quiz 6: Whose blog post did I mention for AsyncTask?
85. JobScheduler
86. JobScheduler • Available only on API 23+
87. JobScheduler • Available only on API 23+ • Framework intelligently schedules and batches tasks
88. JobScheduler • Available only on API 23+ • Framework intelligently schedules and batches tasks • You can specify conditions for execution
89. JobScheduler • Available only on API 23+ • Framework intelligently schedules and batches it • You can specify conditions for execution • System holds a wakelock to ensure the device is awake till job completion
90. JobScheduler • Available only on API 23+ • Framework intelligently schedules and batches it • You can specify conditions for execution • System holds a wakelock to ensure the device is awake till job completion Use case: backup data when WiFi is available
91. WorkManager
92. WorkManager • Provides guarantee that job will be executed
93. WorkManager • Provides guarantee that job will be executed • Backward compatible till API 14
94. WorkManager • Provides guarantee that job will be executed • Backward compatible till API 14 • Survives app or phone restart
95. WorkManager • Provides guarantee that job will be executed • Backward compatible till API 14 • Survives app or phone restart • Allows chaining tasks in different ways
96. WorkManager • Provides guarantee that job will be executed • Backward compatible till API 14 • Survives app or phone restart • Allows chaining tasks in different ways • Should only be used for jobs are not immediate and can be executed at a later time
97. WorkManager • Provides guarantee that job will be executed • Backward compatible till API 14 • Survives app or phone restart • Allows chaining tasks in different ways • Should only be used for jobs are not immediate and can be executed at a later time Use case: sending analytics logs to a server
98. Guidelines
99. Guidelines 1. Is the work immediate?
100. Guidelines 1. Is the work immediate? 2. Does it depend on system conditions?
101. Guidelines 1. Is the work immediate? 2. Does it depend on system conditions? 3. Does it have to happen at a specific time?
102. Quiz 7: What is the title of this talk?
103. Thank You... @iamsubhrajyoti @SubhrajyotiSen