CGPoint relative to view

问题:

Consider a screen point (CGPoint) and a view (UIView), which is somewhere inside the view hierarchy (it can be a subview of other views).

How can you convert the point to a point relative to the view's coordinates?

回答1:

First, convert the point from screen coordinates to the coordinates of your main window:

UIWindow *mainWindow = [[UIApplication sharedApplication] keyWindow];
CGPoint pointInWindowCoords = [mainWindow convertPoint:pointInScreenCoords fromWindow:nil];

Second, convert the point from window coords to view coords:

CGPoint pointInViewCoords = [myView convertPoint:pointInWindowCoords fromView:mainWindow];