https://developer.android.com/reference/android/support/v7/preference/PreferenceGroup?authuser=1
PreferenceGroup | API reference | Android Developers
api referenceandroiddevelopers
https://developer.android.com/reference/android/support/v7/preference/PreferenceGroup.PreferencePositionCallback?authuser=4
PreferenceGroup.PreferencePositionCallback | API reference | Android Developers
api referenceandroiddevelopers