Application context holds activity-specific state

[sacnl]

While Activities are recreated when an app is restarted, Android keeps some things in memory, for example, MD2Application. MD2Application, however, contains references to UI elements (via mappings, possibly also validators) that are specific to one lifecycle. When an activity (but not MD2Application) is created again, the mappings point to stale UI elements and do not have any effect. The global context should not hold references to objects that will be recreated when the apps is newly started.

To see this effect in action, look at the simple app in wwu-pi/md2-testApps@85c2e8a4580eeda64ffdf5cd9931478f2b45ad1f

• close it (via back button)
• open it again => mappings not working
• close it and remove it from cache (Running Services -> Show cached processes)
• open it again => mappings working again, because context has been created anew

[sacnl]

This also leads to errors if an app consists of more than one activity and starts sub-activities multiple times.