On 10-Jun-2011, at 12:44 AM, Matt Neuburg wrote:
> On Wed, 01 Jun 2011 22:25:32 +0800, Roland King <r...@rols.org> said:
>> I've been taking advantage of the fact that UIView's don't clip to their
>> bounds by making my superview of size CGSizeZero and adding content to it.
>> This means I can position the whole view hierarchy using its center, which
>> is always at (0,0). This is very useful as my view has subviews which move
>> all over the place and I really only care about the top left, the superview
>> is just a convenient canvas to hang them on.
>>
>> I got bitten by that today however because none of my subviews get touches,
>> I believe that's because a touch outside the superview bounds is ignored,
>> the views are shown, they aren't clipped, but the touches are 'clipped'.
>>
>> Is there method call to tell a view to hitTest: out of its own bounds, just
>> considering the subviews?
>
> See chapter 18 of my book. Basically, your assessment is exactly right; all
> you have to know is how hit-testing works. You touch outside your view, so as
> the hit-test percolates down through the views it comes to your view and
> asks: was this touch inside you? And your view says no, rightly, and that's
> the end of that; we never get down to your view's subviews.
>
> So clearly all you have to do is modify hit-testing, which is easy: your view
> must test its subviews even if the touch is outside itself. Something like
> this, in your UIView (largely off the top of my head, but this should work to
> get you started):
>
> -(UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
> UIView* result = [super hitTest:point withEvent:event];
> if (result)
> return result;
> for (UIView* sub in [self.subviews reverseObjectEnumerator]) {
> CGPoint pt = [self convertPoint:point toView:sub];
> result = [sub hitTest:pt withEvent:event];
> if (result)
> return result;
> }
> return nil;
> }
>
that's just about exactly what I ended up with .. thanks!
-(UIView*)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
UIView *retval = nil;
// traverse the subviews in backwards order until one returns something
for( UIView *subview in [ [ self subviews ] reverseObjectEnumerator ] )
if( ( retval = [ subview hitTest:[ subview convertPoint:point
fromView:self ] withEvent:event ] ) )
break;
return retval;
}
> m.
>
> --
> matt neuburg, phd = m...@tidbits.com, <http://www.apeth.net/matt/>
> A fool + a tool + an autorelease pool = cool!
> Programming iOS 4!
> http://www.apeth.net/matt/default.html#iosbook
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