Comments on: iPhone Tip: Larger Hit Area for UIButton

By: Marc

Marc — Mon, 09 Jan 2012 02:04:24 +0000

There’s a flaw in the maths here. You’re subtracting the error margin from the origin, and then adding it to the width and height. This cancels out and means it won’t recognise hits below the button or to the right.

The line:
CGRect largerFrame = CGRectMake(0 – errorMargin, 0 – errorMargin, self.frame.size.width + errorMargin, self.frame.size.height + errorMargin);

Should be replaced by:
CGRect largerFrame = CGRectMake(0 – errorMargin, 0 – errorMargin, self.frame.size.width + (errorMargin * 2), self.frame.size.height + (errorMargin * 2));

By: Tyler

Tyler — Tue, 22 Nov 2011 18:58:47 +0000

Actually, using pointInside works better, as your hitTest routine is overriding the isHidden flag. Your button still works even if it is hidden.

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
CGRect rect = CGRectInset([self bounds], -margin, -margin);
return CGRectContainsPoint(rect, point);
}

By: Tyler

Tyler — Tue, 22 Nov 2011 18:52:31 +0000

Nevermind. It behaves in unexpected ways. Ah well.

By: Tyler

Tyler — Tue, 22 Nov 2011 18:36:33 +0000

Instead of using CGRectMake, you could use CGRectInset([self frame],-errorMargin,-errorMargin).

It’s a bit cleaner.

By: kb1ooo

kb1ooo — Tue, 08 Feb 2011 21:25:05 +0000

@bdunagan one correction. +buttonWithType (in addition to using -initWithFrame) will return the proper subclass, but again *only* for UIButtonTypeCustom.

By: kb1ooo

kb1ooo — Tue, 08 Feb 2011 21:01:50 +0000

@bdunagan what do you mean “it just works”. You didn’t show how you created an instance of your subclass? If you are *not* using +buttonWithType then you are stuck at only being able to create UIButtonTypeCustom type buttons. What do you do for the other types? It’s worse than @Michelle suggested because +buttonWithType returns an instance of one of many different private classes depending on the type.

By: bdunagan

bdunagan — Thu, 19 Aug 2010 02:00:12 +0000

@Michelle No need to worry about buttonWithType. If you simply subclass UIButton and override hitTest, it just works. I updated the post with code showing how.

By: Michelle

Michelle — Thu, 01 Apr 2010 19:45:39 +0000

Can you say a bit about how to “programmatically grow button’s hit area via UIView::hitTest”. I’m not clear how you can do that for a UIButton, as buttonWithType always returns a UIButton rather than a subclass.