Lifecycle when pausing AND rotating

Issue

I've got an app that is complete, apart from the lifecycle that, guiltily, I left as last. Things seem to work good in all cases, but one:

• When I pause the app by pressing the power button, it correctly pauses and restarts when resuming.
• When I rotate the screen it correctly resizes.
• When I pause AND THEN rotate the screen, its behaviour is different and the app resets.

Now, obviously it's a problem of my internal code, but to help me in the debugging, I would like to understand what's the difference between the three lifecycles. Or better, if the THIRD example is some how different from the first two.

With debugging I saw that all of three do this (I resemble by mind, I hope to be right):

• onSaveInstanceState()
• onPause()
• onStop()
• onStart()
• onResume()

Is it right? Or do I miss some lifecycle steps in the third example, above?

Thank you.

Solution

Please specify what you mean by the app resets.

When you press the power button, most likely your app stops. That's why you see onStart() being called after stopping (not: pausing) your app.

Given that, is it really the case that the third scenario you describe is a combination of the first two? In other words, how do you pause your app in the third scenario?

Update Regarding your comment: There is a difference between your Activity being stopped and your Activity being destroyed.

Rotation is a configuration change. In this scenario, your Activity is going to be destroyed and re-created. You can handle this case separately if you must (it depends) through the onRetainNonConfigurationInstance() callback and the getLastNonConfigurationInstance() method. Android will call onPause(), onStop(), onRetainNonConfigurationInstance() and onDestroy() in this order, and then continue with onCreate() etc and it will not handle any events in the meantime so that they won't get lost.

Most likely, some of your code is located in the wrong callback, such that in the third scenario, something does not get initialized/attached/... This is really hard to tell without the code and the exception (if it is an exception).

I suggest you proceed as follows.

• Complete your understanding of the lifecycle and be precise (creation, start, restart, resume, pause, stop, destroy)
• Complete your code to override the other lifecycle callbacks as well with log messages (don't forget to call the super class' callback) and analyze pause, stop, rotation and combinations
• Identify the point of the crash
• Analyze the life cycle of the objects involvedd in the crash in conjunction with the Activity lifecycle

Or you can post some code and the exception here, of course.

Update 2 I have made a test on an AVD. I have observed the following:

When the AVD is in landscape orientation, and I press the power button, my app receives a configuration change to portrait orientation (presumably because the portrait-orientation-only lock screen takes over). Pressing power again and unlocking the AVD, the app receives a configuration change again back to landscape orientation.

While not solving your issue, it goes to show that code must be carefully placed in the respective callbacks, because in the case above, while being re-created, the Activity will still not be shown.

Drop me a comment if you update your question.

Answered By - class stacker