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
   

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2. The Main Thread
   

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3. The Main Thread
   ●
   Default thread that apps start on
   

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4. The Main Thread
   ●
   Default thread that apps start on
   ●
   Known as the UI thread
   

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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
   

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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
   

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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
   

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8. The Main Thread is Precious
   

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9. The Main Thread is Precious
   ●
   Refreshed at a regular interval
   

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10. The Main Thread is Precious
    ●
    Refreshed at a regular interval
    ●
    Should be never blocked
    

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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
    

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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...
    

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14. The Solution
    

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15. The Solution
    Do work in the background
    

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16. The Solution
    Do work in the background
    When the user is
    using the app
    

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17. The Solution
    Do work in the background
    When the user is
    using the app
    When the user is not
    using the app
    

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18. Why is background work challenging?
    

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19. A process is not forever
    - Keith Smith
    

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20. The Process Priority Table
    

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21. The Process Priority Table
    1. Native
    

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22. The Process Priority Table
    1. Native
    2. System
    

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23. The Process Priority Table
    1. Native
    2. System
    3. Persistent Apps
    

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24. The Process Priority Table
    1. Native
    2. System
    3. Persistent Apps
    4. Foreground Apps
    

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25. The Process Priority Table
    1. Native
    2. System
    3. Persistent Apps
    4. Foreground Apps
    5. Perceptible Apps
    

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26. The Process Priority Table
    1. Native
    2. System
    3. Persistent Apps
    4. Foreground Apps
    5. Perceptible Apps
    6. Service
    

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27. The Process Priority Table
    1. Native
    2. System
    3. Persistent Apps
    4. Foreground Apps
    5. Perceptible Apps
    6. Service
    7. Home
    

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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
    

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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
    

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30. Solutions by Android
    

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31. Solutions by Android
    AsyncTask
    Coroutines
    RxJava
    AlarmManager
    Foreground Service
    Loader
    Thread and Handler
    Intent Service
    WorkManager Job Scheduler
    

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32. So many solutions!!!
    
    

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33. BUT WHY
    
    

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34. Changes Introduced in the OS
    

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35. Changes Introduced in the OS
    Android 6.0 introduced Doze
    Source: developer.android.com
    

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36. Changes Introduced in the OS
    ●
    Android 7.0 introduced Doze on the Go
    

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37. Changes Introduced in the OS
    ●
    Android 7.0 introduced Doze on the Go
    ●
    Android 8.0 introduced
    ○
    Background Service Limitations
    ○
    Broadcast Limitations
    

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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
    

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39. App Standby Buckets
    

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40. App Standby Buckets
    ●
    Use machine learning to determine how likely each app will be
    used.
    

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41. App Standby Buckets
    ●
    Use machine learning to determine how likely each app will be
    used.
    ●
    Places app in one of 5 priority buckets
    

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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
    

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43. The “Not Recommended” Solutions
    

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44. AsyncTask
    

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45. AsyncTask
    ●
    Does not auto-cancel when Activity/Fragment is
    destroyed/recreated
    

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46. AsyncTask
    ●
    Does not auto-cancel when Activity/Fragment is
    destroyed/recreated
    ●
    Can lead to memory leaks
    

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47. AsyncTask
    ●
    Does not auto-cancel when Activity/Fragment is
    destroyed/recreated
    ●
    Can lead to memory leaks
    ●
    Not really easy to cancel
    

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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
    

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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
    

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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
    

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51. Quiz 1:
    What feature of Android Pie did I mention that
    intelligently prioritizes apps?
    

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52. Quiz 2:
    Name any 3 buckets from the App Standy
    Buckets
    

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53. Loaders
    

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54. Loaders
    ●
    Deprecated on Android P (API 28)
    

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55. Loaders
    ●
    Deprecated on Android P (API 28)
    ●
    Confusing API
    

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56. Loaders
    ●
    Deprecated on Android P (API 28)
    ●
    Confusing API
    ●
    Can be unpredictable
    

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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
    

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58. The “Recommended” Solutions
    

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59. DownloadManager
    

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60. DownloadManager
    ●
    Perform long-running HTTP downloads
    

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61. DownloadManager
    ●
    Perform long-running HTTP downloads
    ●
    Handles HTTP interaction
    

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62. DownloadManager
    ●
    Perform long-running HTTP downloads
    ●
    Handles HTTP interaction
    ●
    Retry on failure
    

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63. DownloadManager
    ●
    Perform long-running HTTP downloads
    ●
    Handles HTTP interaction
    ●
    Retry on failure
    ●
    Continuation after reboot
    

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64. DownloadManager
    ●
    Perform long-running HTTP downloads
    ●
    Handles HTTP interaction
    ●
    Retry on failure
    ●
    Continuation after reboot
    ●
    Handles connectivity changes
    

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65. DownloadManager
    ●
    Perform long-running HTTP downloads
    ●
    Handles HTTP interaction
    ●
    Retry on failure
    ●
    Continuation after reboot
    ●
    Handles connectivity changes
    ●
    Notifies user of progress updates
    

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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
    

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67. Quiz 3:
    Which API level was Loader deprecated in?
    

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68. Quiz 4:
    What should you use to replace Loader?
    

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69. Foreground Services
    

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70. Foreground Services
    ●
    High priority is the process ranking system.
    

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71. Foreground Services
    ●
    High priority is the process ranking system.
    ●
    Non-dismissible notification
    

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72. Foreground Services
    ●
    High priority is the process ranking system.
    ●
    Non-dismissible notification
    ●
    Should be used for immediate, important tasks
    

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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
    

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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)
    

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75. Quiz 5:
    What would be the priority rank of Foreground
    Service in the Process Priority Table?
    

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76. AlarmManager
    

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77. AlarmManager
    ●
    Schedule tasks at a particular time
    

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78. AlarmManager
    ●
    Schedule tasks at a particular time
    ●
    Schedule tasks to execute at intervals
    

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79. AlarmManager
    ●
    Schedule tasks at a particular time
    ●
    Schedule tasks to execute at intervals
    ●
    Available since API 1
    

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80. AlarmManager
    ●
    Schedule tasks at a particular time
    ●
    Schedule tasks to execute at intervals
    ●
    Available since API 1
    Gotchas:
    

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81. AlarmManager
    ●
    Schedule tasks at a particular time
    ●
    Schedule tasks to execute at intervals
    ●
    Available since API 1
    Gotchas:
    ●
    Alarms reset after phone reboot
    

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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
    

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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
    

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84. Quiz 6:
    Whose blog post did I mention for AsyncTask?
    

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85. JobScheduler
    

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86. JobScheduler
    ●
    Available only on API 23+
    

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87. JobScheduler
    ●
    Available only on API 23+
    ●
    Framework intelligently schedules and batches tasks
    

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88. JobScheduler
    ●
    Available only on API 23+
    ●
    Framework intelligently schedules and batches tasks
    ●
    You can specify conditions for execution
    

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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
    

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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
    

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91. WorkManager
    

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92. WorkManager
    ●
    Provides guarantee that job will be executed
    

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93. WorkManager
    ●
    Provides guarantee that job will be executed
    ●
    Backward compatible till API 14
    

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94. WorkManager
    ●
    Provides guarantee that job will be executed
    ●
    Backward compatible till API 14
    ●
    Survives app or phone restart
    

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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
    

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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
    

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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
    

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98. Guidelines
    

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99. Guidelines
    1. Is the work immediate?
    

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100. Guidelines
     1. Is the work immediate?
     2. Does it depend on system conditions?
     

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101. Guidelines
     1. Is the work immediate?
     2. Does it depend on system conditions?
     3. Does it have to happen at a specific time?
     

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102. Quiz 7:
     What is the title of this talk?
     

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103. Thank You...
     @iamsubhrajyoti @SubhrajyotiSen
     

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