For these who are going to selling phone , and clean phone space , and for other reason to clear Android phone ,as far as I am concerned at the some time , the Android data are not easy to permanently erase from phone,this involves the safety problems of important data, if the "Delete "button can permanently delete everything from Android phone , how terrible, it will ,lead to more trouble
I won't deny your idea, to permanently delete everything from Android phone , it is not as simple as we think .because you don't know if the deleted data still has a chance to get back ,there is a tutorial that you can read :
mobiledic.com/android-topic ... phone.html