Slider on my PreferenceScreen

You could create your own Preference class that extends DialogPreference and shows a SeekBar as the dialog view.

If you already moved to androidX you can simply use androidx.preference.SeekBarPreference. Documentation here and here

Define it in XML like this:

<SeekBarPreference
        app:defaultValue="8"
        app:key="COUNT_SPEED"
        app:title="Fast count speed"
        />

Note: Now in Android Studio (my current version is 3.2.1) auto-suggestions doesn't work for androidx.preference.PreferenceScreen in prefs.xml, but don't worry inflating settings from xml with setPreferencesFromResource() works fine. All needed attributes names and component references you can find here.