Preference change listener but AFTER the internal state has changed android

Question

I have a SettingsFragment which extends PreferenceFragmentCompat and the preference.xml

class SettingsFragment : PreferenceFragmentCompat() {

   override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val view = super.onCreateView(inflater, container, savedInstanceState)

        preferenceManager.findPreference<Preference>(USER_CLOUD_PROXY)?.let {
            it.setOnPreferenceChangeListener { _, _ ->
                // mainViewModel.resetConnection()
                true
            }
        }

        return view
    }

}

and xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">

    <PreferenceCategory android:title="User settings">
        <SwitchPreference
            android:defaultValue="true"
            android:enabled="true"
            android:key="user_cloud_proxy"
            android:title="Use cloud proxy" />
    </PreferenceCategory>

</PreferenceScreen>

The switch button indicates with which URL my app has to connect to a webSocket server. So when the user changes the switch state i want to reset the connection through a function. Later in the function i read the sharedPreference value to choose the URL. However, the it.setOnPreferenceChangeListener get called before the internal state has changed, which means that i dont read the newValue, but the old.

Is there a callback that gets called AFTER the internal value has changed?

Answer 1

There is OnPreferenceChangeInternalListener.onPreferenceChange which is Called when this Preference has changed, but this callback is for internal usage only.

So yes, there is no other callback that gets called after the internal value has changed. OnPreferenceChangeListener.onPreferenceChange is the only one you can use.

One thing you can do, if you don't want to call the function directly from the callback taking the newValue from it, then you can save the new value in SharedPref manually and then call the function which can use your logic of reading the value from sharedpref and proceeding further.

Answer 2

Adding to dinkar_kumar's answer you can try to implement OnSharedPreferenceChangeListener and I think you can use onSharedPreferenceChanged to use your logic further.

Answer 3

Thank you, well informed! i will do this the way u propose. Seems fine

Answer 4

As I have tested, if you have an async task, it will be run after the internal state has changed like below:

Kotlin Sample Code:

Preference.OnPreferenceChangeListener { _, _ ->
    afterChange()
    true
}


fun afterChange() {
    // coroutine async task
    MainScope().launch {
        // It will run after the preference has been changed.
    }
}