滚动视图只检测从某些区域滚动?

I want to have a scrollview that covers the entire screen. However I want to know if it is possible to only allow scrolling to be detected from part of the scrollview. For example you have a full screen scroll view the top half of the screen should detect scrolling but the bottom half should not. I know if you change the alpha to 0 the scrollview doesn't scroll anymore, would a possible solution be to change the alpha of part of the scrollview? is that even possible? any thoughts or ideas?I want to have a scrollview that covers the ent