如何监听片段中的首选项更改？

Question

Lots of similar questions but I still can't find an answer. So I have a Fragment where I want to listen for changes in a PreferenceActivity .

The documentation says to register the listener in onResume() and un-register in onPause() :

For proper lifecycle management in the activity, we recommend that you register and unregister your SharedPreferences.OnSharedPreferenceChangeListener during the onResume() and onPause() callbacks, respectively:

I assume they are referring to registering the listener from within the PreferenceActivity onResume/onPause methods, since if you unregister the listener in the Fragment's onPause() , then it will not listen for the changes.

So is the solution to do the opposite ie - register in onPause() and un-register in onResume() ?

Thanks!

Answer 1

It's not the PreferenceActivity that notify the changes on the preferences but the SharedPreferences it's self. The PreferenceActivity is a meare user interface to access the SharedPreferences .

So if it's your fragment that needs to listen for SharedPreferences changes it should be the one to register for changes. In other words let your fragment implement the OnSharedPreferenceChangeListener and register for this changes on the fragment onResume and unregister onPause as the doc say.

You also need to load the preference on the fragment onResume so when it goes onPause then onResume the current state of the preference is loaded.

See also https://stackoverflow.com/a/13596569/665823