I have read Apple Scroll View Programming Guide for iOS but still confused about the following part:
Scrolling to a Specific Offset
Scrolling to a specific top-left location (the contentOffset property)
can be accomplished in two ways. The setContentOffset:animated: method
scrolls the content to the specified content offset. If the animated
parameter is YES, the scrolling will animate from the current position
to the specified position at a constant rate. If the animated
parameter is NO, the scrolling is immediate and no animation takes
place. In both cases, the delegate is sent a scrollViewDidScroll:
message. If animation is disabled, or if you set the content offset by
setting the contentOffset property directly, the delegate receives a
single scrollViewDidScroll: message. If animation is enabled, then the
delegate receives a series of scrollViewDidScroll: messages as the
animation is in progress. When the animation is complete, the delegate
receives a scrollViewDidEndScrollingAnimation: message.Making a rectangle visible
It is also possible to scroll a rectangular area so that it is
visible. This is especially useful when an application needs to
display a control that is currently outside the visible area into the
visible view. The scrollRectToVisible:animated: method scrolls the
specified rectangle so that it is just visible inside the scroll view.
If the animated parameter is YES, the rectangle is scrolled into view
at a constant pace. As with setContentOffset:animated:, if animation
is disabled, the delegate is sent a single scrollViewDidScroll:
message. If animation is enabled, the delegate is sent a series of
scrollViewDidScroll: messages as animation progresses. In the case of
scrollRectToVisible:animated: the scroll view’s tracking and dragging
properties are also NO.If animation is enabled for scrollRectToVisible:animated:, the
delegate receives a scrollViewDidEndScrollingAnimation: message,
providing notification that the scroll view has arrived at the
specified location and animation is complete.
I think it is quite similar between setContentOffset:animated and scrollRectToVisible:animated, could someone give some hints about them?
And scrollRectToVisible:animated: is similar to scrollViewDidEndDecelerating:animated: too.
Short answer:
setContentOffset:animated preserves the zoomscale.
scrollRectToVisible:animated may change it.