Which lifecycle event is best to register/unregister listeners?

I have manager classes that take an activity as a listener. I use the managers to do threaded calls, work etc and then call back to the listener(activity) when things are done, need changed and so on.

I want to register and unregister the activity as a listener when it is no longer visible. This will prevent unwanted changes from happening (like dialogs appearing when the activity is no longer visible).

My question is, what lifecycle events are best to do this registering. I started with onPause() and onResume() which worked well except when I had an activity that was doing stuff in onActivityResult(). Since onActivityResult() gets called before onResume() my managers are not always reg开发者_Go百科istered in time.

Do I need to register in onResume() AND onActivityResult() or is there a better way to approach this?

An alternative approach may be to postpone the processing currently done in onActivityResult() until after the listeners are registered in onResume().

Possible ways of doing this include posting to the message queue, e.g. using a Handler, setting a Runnable object to be called by onResume, or simply storing the result data received by onActivityResult().

This would also ensure that the activity really has come to the foreground when the listener methods are called.

onResume() and onPause() are the best for this. The onDestroy(), per the documentation, is not guaranteed to be invoked though this is a favorite for many people, so stick with the pauses and resumes.

You can have the handle of the current Activity in the Manager class. Register its presence on onCreate() and unregister it on either onCreate() by some other Activity, or onBackPressed() of the current Activity.

On a related note, I would recommend an MVC (or similar) architecture where the controller has awareness of the view's status (the controller can track the onCreate() and onBackPressed() of each Activity).