Data loss on double screen rotation

[davirec]

Hi, this issue has a relation with #195.

A data loss problem occurs when data is accidentally deleted or state variables are accidentally assigned with default or initial values. This issue is related to the activity's lifecycle (1). When a screen rotation occurs, the activity is destroyed and resumed. Data loss will happen if the developer does not save the variables before the destruction and restore them after creation. To avoid this, the developers have to implement both the logic necessary to save the activity state in the onSaveInstanceState() callback method and the logic to resume its state in the onRestoreInstanceState() callback method.
Another way to avoid data loss problems is to use the view model, designed to store and manage UI-related data in a lifecycle-conscious way (2).

We found failures similar to the #195 issue in the activity

• MainActivity: Top bar text disappears, Topbar text changes, various view properties change, fragment with typeable text disappears, message in top bar appears, pop up menu disappears, screen scroll and activity resets.
• SettingsActivity: fragment disappears;

Top bar text disappears.

Before and after double screen rotation

Top bar text changes

Before and after double screen rotation

Various view properties change.

LongTouchEvent(duration=2000) [[622,54],[720,138]]
KeyEvent(name=BACK)
IntentEvent(intent='am start com.github.ruleant.getback_gps/com.github.ruleant.getback_gps.MainActivity')
KeyEvent(name=BACK)
IntentEvent(intent='am start com.github.ruleant.getback_gps/com.github.ruleant.getback_gps.MainActivity')
ScrollEvent(direction=FULL_LEFT)
IntentEvent(intent='am start com.github.ruleant.getback_gps/com.github.ruleant.getback_gps.MainActivity')
TouchEvent [[272,54],[522,138]]
TouchEvent [[46,910],[307,1005]]
LongTouchEvent(duration=2000) [[622,54],[720,138]]
TouchEvent [[524,54],[622,138]]
Cap01: capture screen properties before rotation
DoubleRotationEvent
Cap02: capture screen properties after rotation
Cap01 != Cap02 (lost several properties)

Fragment with typeable text disappears.

Before and after double screen rotation

Message in top bar appears.

Before and after double screen rotation

The pop-up menu disappears.

Before and after double screen rotation

Before and after double screen rotation

Fragment disappears

Before and after double screen rotation

Note:

• Double screen rotation: It is executed twice to reach a state that should be exactly the same as the screen before if no data loss occurred.
• A data loss problem occurs when data is accidentally deleted or state variables are accidentally assigned with default or initial values.

1. https://developer.android.com/guide/components/activities/activity-lifecycle
2. https://developer.android.com/topic/libraries/architecture/viewmodel