The user needs to have the ability to change his system font through using my new application. So how can I get a port of “Font style” in my application from the preferences item which is located under “Settings -> Display -> Screen Display -> Font Style” ?
Also, I searched for “Font style” in the Android source code and wasn’t able to find it.
That does not exist in standard Android. There is no system-wide “font style” setting. Your specific device might offer that setting, in which case it probably affects only the built-in apps.