Where Did My State Go? - WWC Mobile

Transcript

1. Where Did My State Go? Subhrajyoti Sen KeepTruckin @iamsubhrajyoti
2. This is a state management talk
3. This is a Lifecycle talk
4. The First thing
5. The First thing We have all done this
6. The First thing We have all done this <activity android:name=".main.MainActivity" android:screenOrientation="portrait">
7. Is this Enough?
8. NO
9. NO
10. But WHY?
11. Reasons
12. Reasons 1. Dark Theme
13. Reasons 1. Dark Theme 2. Multi-Window
14. Reasons 1. Dark Theme 2. Multi-Window 3. Process Death
15. Reasons 1. Dark Theme 2. Multi-Window 3. Process Death 4. Changing Language/ Font Scale
16. Reasons 1. Dark Theme 2. Multi-Window 3. Process Death 4. Changing Language/ Font Scale 5. Permission Revocation
17. Dark Theme
18. Dark Theme Introduced in Android 10
19. Dark Theme Introduced in Android 10 Can be changed by 1. System Toggle 2. AppCompat in-app
20. Dark Theme
21. Dark Theme Triggers a uiMode configuration change
22. Dark Theme Triggers a uiMode configuration change All started Activities are automatically recreated.
23. Dark Theme <activity android:name=".MyActivity" android:configChanges="uiMode" />
24. Dark Theme <activity android:name=".MyActivity" android:configChanges="uiMode" /> This will invoke onConfigurationChanged() and not recreate all started Activities.
25. Multi-Window
26. Multi-Window
27. Multi-Window
28. Multi-Window Introduced in Android N
29. Multi-Window Introduced in Android N A slight change in Lifecycle.
30. Multi-Window Introduced in Android N A slight change in Lifecycle. You can’t completely depend on onPause() and onResume()
31. Multi-Window Introduced in Android N A slight change in Lifecycle. You can’t completely depend on onPause() and onResume() screenOrientation will be ignored
32. Multi-Window Portrait orientation != Vertical device
33. Multi-Window Portrait orientation != Vertical device android:resizeableActivity="false" to opt out of Multi-Window
34. Process Death
35. Process Death • The device is running low on memory and the OS kills your app to free up memory.
36. Process Death • The device is running low on memory and the OS kills your app to free up memory. • It happens if your app is in the Paused/Stopped state.
37. Process Death • The device is running low on memory and the OS kills your app to free up memory. • It happens if your app is in the Paused/Stopped state. • Cannot work around it.
38. Process Death - Testing 1. Developer Options -> Apps -> Background process limit 2. Choose ‘No background processes’ 3. Open your app and put in the background 4. Open another app and switch to your app
39. Process Death - Testing 1. Put the app in background 2. adb shell am kill packagename
40. Process Death - Testing
41. ViewModel
42. ViewModel ViewModels persist state across Activity recreation. ViewModels do not persist state on process death.
43. ViewModel ViewModels persist state across Activity recreation. ViewModels do not persist state on process death. Use SavedStateHandle to save state.
44. ViewModel - SavedStateHandle
45. ViewModel - SavedStateHandle val viewModel = ViewModelProvider(this, SavedStateVMFactory(this)) .get(MyViewModel::class.java)
46. ViewModel - SavedStateHandle val viewModel = ViewModelProvider(this, SavedStateVMFactory(this)) .get(MyViewModel::class.java) class MyViewModel(val state : SavedStateHandle) : ViewModel() { fun saveProductId(productId: String) { state.set("productId", productId) } fun getProductId(): String { return state.get("productId")?: "" } }
47. onSaveInstanceState is still valid class ProfileBottomSheet() : BottomSheetDialogFragment() { private lateinit var name: String override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) button.setOnClickListener { name = editText.text.toString()} } override fun onSaveInstanceState(outState: Bundle) { outState.putString("name", name) super.onSaveInstanceState(outState) } }
48. Custom View Views can save their own state. Views need to have an ID to be able to save state.
49. Custom View private class SavedState : BaseSavedState { var value = 1 constructor(superState: Parcelable) : super(superState) private constructor(source: Parcel) : super(source) { value = source.readInt() } override fun writeToParcel(out: Parcel, flags: Int) { super.writeToParcel(out, flags) out.writeInt(value) } }
50. Custom View private class SavedState : BaseSavedState { //.. companion object { val CREATOR: Parcelable.Creator<SavedState> = object : Parcelable.Creator<SavedState> { override fun createFromParcel(source: Parcel) = SavedState(source) override fun newArray(size: Int) = arrayOfNulls<SavedState?>(size) } } }
51. Custom View class CustomView(context: Context) : View(context) { var value = 1 override fun onSaveInstanceState(): Parcelable { val superState = super.onSaveInstanceState() val state = SavedState(superState) state.value = this.value return state } }
52. Custom View class CustomView(context: Context) : View(context) { override fun onRestoreInstanceState(state: Parcelable) { val savedState = state as SavedState super.onRestoreInstanceState(savedState.superState) this.value = savedState.value } }
53. Fragment class ProfileBottomSheet(val name: String) : BottomSheetDialogFragment() { override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) textview.setText(name) } }
54. Fragment - Use Bundle val profileBottomSheet = ProfileBottomSheet() profileBottomSheet.arguments = Bundle().apply { putString("name", "subhrajyoti") }
55. What about TESTING?
56. Testing Activity/Fragment Recreation
57. Testing Activity/Fragment Recreation Can be done with Espresso
58. Testing Activity/Fragment Recreation Can be done with Espresso Easier with AndroidX Test
59. Testing Activity/Fragment Recreation Can be done with Espresso Easier with AndroidX Test debugImplementation 'androidx.fragment:fragment-testing:$fragment_version'
60. Testing Fragment Recreation
61. Testing Fragment Recreation @RunWith(AndroidJUnit4::class) class MyTestSuite { @Test fun testRecreation() { val scenario = launchFragmentInContainer<MyFragment>() } }
62. Testing Fragment Recreation @RunWith(AndroidJUnit4::class) class MyTestSuite { @Test fun testRecreation() { val scenario = launchFragmentInContainer<MyFragment>() // perform actions } }
63. Testing Fragment Recreation @RunWith(AndroidJUnit4::class) class MyTestSuite { @Test fun testRecreation() { val scenario = launchFragmentInContainer<MyFragment>() // perform actions scenario.recreate() } }
64. Testing Fragment Recreation @RunWith(AndroidJUnit4::class) class MyTestSuite { @Test fun testRecreation() { val scenario = launchFragmentInContainer<MyFragment>() // perform actions scenario.recreate() // test events } }
65. Testing Fragment Lifecycle
66. Testing Fragment Lifecycle @RunWith(AndroidJUnit4::class) class MyTestSuite { @Test fun testLifecycle() { val scenario = launchFragmentInContainer<MyFragment>() } }
67. Testing Fragment Lifecycle @RunWith(AndroidJUnit4::class) class MyTestSuite { @Test fun testLifecycle() { val scenario = launchFragmentInContainer<MyFragment>() scenario.moveToState(State.CREATED) } }
68. Resources https://andrewbailey.dev/falsehoods/lifecycles https://www.techyourchance.com/testing-android-applications-killing/
69. Thank You @iamsubhrajyoti