将UIView原点点转换为其窗口坐标系统

I want to get the origin of scrollView in the window coordinate system. For Example, presently, scollView origin is (0,51). But in window coordinate system it should be 51 + 44(navigation bar height)+20(status bar height) = 115. Means in window coordinate system the scrollView.frame.origin should be (0,115). I tried with convertPoint: methods but getting (0,51) or (0,0) sometimes. Please provide a solution to this. ThanksI want to get the origin of scrollView in the w