Comments on: Differentiating Tap Counts on iOS [UPDATED]

By: yar2050

yar2050 — Fri, 19 Nov 2010 19:49:30 +0000

Thank you for leaving this as the post + the update. The method without gesture recognizers is an important thing to have on file, too.

By: Matt Long

Matt Long — Tue, 15 Jun 2010 16:13:28 +0000

@jamie314, @Adion,

Right you are. 350 milliseconds. Fixed!

Thanks.

-Matt

By: Matt Long

Matt Long — Tue, 15 Jun 2010 15:55:55 +0000

@aclark

Nice! Had missed the requireGestureRecognizerToFail method. That's great! I've got some re-factoring to do now, you big jerk. ;-)

Will update the blog post too.

-Matt

By: PBenz

PBenz — Tue, 15 Jun 2010 14:25:32 +0000

I tried this out last night and discovered that aclark’s suggestion of using gestures actually works, but Matt is also correct in that if you put a breakpoint in the handler for the single tap, it will get called. My test code simply NSLogs a line to the console, and the single tap handler definitely does not get called unless there’s a breakpoint set within it. I must admit that I don’t understand why.

By: jamie314

jamie314 — Tue, 15 Jun 2010 11:23:43 +0000

In the interest of picking nits:

The method -peformSelector:withObject:afterDelay: takes a delay in seconds, so 0.35 translates to 350 milliseconds, not 35.

It isn't hugely relevant in this example, but depending on your application an intentional delay of 350ms may become noticeable to users.

By: Adion

Adion — Tue, 15 Jun 2010 08:16:37 +0000

I suppose you meant 350 milliseconds, since the source code says 0.35, which I would assume are seconds.

By: aclark

aclark — Tue, 15 Jun 2010 05:19:46 +0000

Actually you can do this with UIGestureRecognizer. After creating your two (or more) recognizers simply instruct the single-tap recognizer that it can only succeed after the double-tap recognizer fails.

UITapGestureRecognizer *singleTap, *doubleTap;

singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(singleTap)];
doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doubleTap)];

doubleTap.numberOfTapsRequired = 2;

[singleTap requireGestureRecognizerToFail:doubleTap];

[view addGestureRecognizer:singleTap];
[view addGestureRecognizer:doubleTap];

In that way the singleTap recognizer will only have its action invoked if there is a delay between two taps longer than what the system has determined qualifies a double-tap. No magic numbers required.

By: Matt Long

Matt Long — Mon, 14 Jun 2010 23:43:36 +0000

@ cpryland

Gestures don't fix the problem. Try creating two gesture recognizers--one that responds to two taps and one that responds to one. Then set a break point in them both. If you double tap, they both still get called.

Best regards.

By: cpryland

cpryland — Mon, 14 Jun 2010 23:29:51 +0000

Gosh, shouldn’t you just assume 3.2 and use the gesture support?