UIView has the properties frame, bounds, center, and origin, and they all seem to be interrelated. Most of the time, I deal with frame when setting the position and size of a UIView. I understand that frame is using global coordinate system and bounds is using coordinate of the local view (therefore its x and y are 0, but not always), but it's still confusing to me when to use what.
Under what context (and what's the right time) the other properties (bounds, center, origin) should be used?
The properties center, bounds and frame are interlocked: changing one will update the others, so use them however you want. For example, instead of modifying the x/y params of frame to recenter a view, just update the center property.
They are related values, and kept consistent by the property setter/getter methods (and using the fact that frame is a purely synthesized value, not backed by an actual instance variable).
The main equations are:
frame.origin = center - bounds.size / 2
(which is the same as)
center = frame.origin + bounds.size / 2
(and there’s also)
frame.size = bounds.size
That's not code, just equations to express the invariant between the three properties. These equations also assume your view's transform is the identity, which it is by default. If it's not, then bounds and center keep the same meaning, but frame can change. Unless you're doing non-right-angle rotations, the frame will always be the transformed view in terms of the superview's coordinates.
This stuff is all explained in more detail with a useful mini-library here:
Source: Stackoverflow.com