Question
Mobile Safari allows you to switch pages by entering a sort of UIScrollView horizontal paging view with a page control at the bottom.
I am trying to replicate this particular behavior where a horizontally scrollable UIScrollView shows some of the next view's content.
The Apple provided example: PageControl shows how to use a UIScrollView for horizontal paging, but all views take up the whole screen width.
How do I get a UIScrollView to show some content of the next view like mobile Safari does?
Answer
A UIScrollView with paging enabled will stop at multiples of its frame width
(or height). So the first step is to figure out how wide you want your pages
to be. Make that the width of the UIScrollView. Then, set your subview's
sizes however big you need them to be, and set their centers based on
multiples of the UIScrollView's width.
Then, since you want to see the other pages, of course, set clipsToBounds to
NO as mhjoy stated. The trick part now is getting it to scroll when the user
starts the drag outside the range of the UIScrollView's frame. My solution
(when I had to do this very recently) was as follows:
Create a UIView subclass (i.e. ClipView) that will contain the
UIScrollView and it's subviews. Essentially, it should have the frame of
what you would assume the UIScrollView would have under normal
circumstances. Place the UIScrollView in the center of the ClipView. Make
sure the ClipView's clipsToBounds is set to YES if its width is less
than that of its parent view. Also, the ClipView needs a reference to the
UIScrollView.
The final step is to override - (UIView *)hitTest:withEvent: inside the
ClipView.
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
return [self pointInside:point withEvent:event] ? scrollView : nil;
}
This basically expands the touch area of the UIScrollView to the frame of
its parent's view, exactly what you need.
Another option would be to subclass UIScrollView and override its - (BOOL)pointInside:(CGPoint) point withEvent:(UIEvent *) event method, however
you will still need a container view to do the clipping, and it may be
difficult to determine when to return YES based only on the UIScrollView's
frame.
NOTE: You should also take a look at Juri Pakaste'shitTest:withEvent: modification if you are having issues with subview user interaction.
