App Lifecycle and Common Problems by Alan Le Corre

Transcript

1. App Lifecycle and common problems by Alan Le Corre @alanlecorre on Slack - GDG Android Montréal
2. Activity lifecycle
4. Fragment Lifecycle
5. How I picture it onCreate() onStart() onResume() onPause() onStop() onDestroy() Visible
6. What happens when…? - we background the App - we close the device - we kill the app - we launch another Activity onCreate() onStart() onResume() onPause() onStop() onDestroy() Visible Demo
7. Demo What code to put where? What are the most used methods? onCreate() onStart() onResume() onPause() onStop() onDestroy() Visible
8. Subscribe / unsubscribe
9. Demo Do you see a bug in the current code? onCreate() onStart() onResume() onPause() onStop() onDestroy() Visible
10. Activity Back Stack • How to monitor your stack? adb shell dumpsys activity activities
12. Beware of killable methods Demo
13. Beware of reused Activities onCreate() onStart() onResume() onPause() onStop() onDestroy() Visible Demo
14. Advice: when entering onResume() do NOT put hypothesis on App states like: • We have data fetched by a previous Activity • The user is logged in (if applicable) • The Activity stack is as expected • … How to pass data to the Activity / Fragment? onCreate() onStart() onResume() onPause() onStop() onDestroy() Visible
15. How to pass data? Note: Do not inject Data in Activity / Fragment with setter Demo
16. Get result from an Activity Demo
17. Brushing over Difficult problems
18. Handling rotations Data or UI state can be lost when doing a device rotation What do you do to solve it?
22. The infamous onSaveInstanceState()
26. What happens? • Usually, the Activity / Fragment state is saved (Example: App in Background) • An event modify his state (Examples: Network Response, Animation End)
27. Any quick solution?
28. Sum up onCreate() onStart() onResume() onPause() onStop() onDestroy() Visibl • Use the Reference Doc https://developer.android.com • Check how you launch and finish your Activities • unsubscribe listeners if applicable • Pass data the right way
29. Questions?