How to update a Preference with a SummaryProvider in a PreferenceFragmentCompat?

Question

In androidx.preference.Preference (using Version 1.1.0-beta01) it is possible to set a summary provider, which I did inside the onCreatePreferences method of a PreferenceFragmentCompat.

override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
  ...

  val mySummaryProvider = Preference.SummaryProvider<Preference> {
     val str = preferenceManager.sharedPreferences.getString(it.key, "")
     doSomethingCool(str)
  }

  findPreference<Preference>("my_pref_id").summaryProvider = mySummarProvider
}

When I now update the preference (by using the preference editor) while the fragment is still visible, how do I notify the preference or the fragment that the summary provider should be called again (it isn't done automatically)? Unfortunately, I don't see any method or way to do that.

Katy

Answer 1

    public class SettingsClass extends PreferenceFragmentCompat {
        @Override
        public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
            addPreferencesFromResource(R.xml.settings_prefs);

            final SwitchPreferenceCompat switchPreferenceCompat = (SwitchPreferenceCompat) getPreferenceManager().findPreference("rememberME");
            switchPreferenceCompat.setSummaryProvider(new Preference.SummaryProvider() {
                @Override
                public CharSequence provideSummary(Preference preference) {
                    if (switchPreferenceCompat.isChecked()) {
                        return "Active";
                    }
                    return "Inactive";


                }
            });
    }}

//.xml file
<PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    app:key="test">
    <PreferenceCategory android:title="Σύνδεση">
    <SwitchPreferenceCompat
        app:key="rememberME"
        android:defaultValue="false"
        app:title="Παραμείνετε Συνδεδεμένος" />
    </PreferenceCategory>
</PreferenceScreen>

Carioca

Answer 2

SummaryProvider is mostly intended to be used for updating the summary of a preference after it updates itself, such as when an option in a ListPreference is selected, forcing an update of the Preference and hence triggering the SummaryProvider.

If you are typically changing the data underneath the preference, do you need a SummaryProvider here? If not, you could just manually call setSummary when you change the data, since Preferences currently don't observe their backing data source. It's hard to tell without more sample code, but it seems strange that the data can change without the user's input, while they are currently viewing the preferences.

Bloodyminded

In my case, I have a preference that opens a system dialog (by using an intent) to select a ringtone (which is set in onActivityResult of the settings fragment). So the specific setting is changed in the background. In the end, I followed your second suggestion and switched over to setSummary in a preference change listener. But I still think that SummaryProvider would be nicer if only a way to notify of updates would be supported. – Katy

Answer 3

I am having a bit trouble to understand the issue, but I would use setSummaryProvider only to update the summary and use a ChangeListener to update other stuff:

        with(findPreference<ListPreference>(PREFKEY_DOWNLOAD_SERVER)!!) {
            setSummaryProvider { pref ->
                getString(R.string.pref_download_server_summary, (pref as ListPreference).value)
            }
            setOnPreferenceChangeListener { _, newValue -> DataLoader.setSelectedServer(newValue as String); true }
        }

Floreneflorentia