Double-tap or two single-taps?

Question

What is the time limit for two taps to be considered a double-tap, on the iPhone OS?

// Edit: Why is this important?

In order to handle single-tap and double-tap differently, Apple's guide says to do performSelector...afterDelay with some 'reasonable' interval on first tap (and cancel it later if the second tap is detected).

The problem is that if the interval is too short (0.1), the single tap action will be performed even when double-tapping (if relying only on tapCount, that is). If it's too long (0.8), the user will be waiting unnecessarily for the single-tap to be recognized, when there is no possibility for a double-tap.

It has to be exactly the correct number, in order to work optimally, but definitely not smaller, or there's a chance for bugs (simultaneous single-tap and double-tap).

Answer 1

On windows (and I'd guess most other systems) this is a system settings so you should look for an API that returns this. (the term "double click" might get more hits from Google)

Answer 2

I don't believe there is a default time-limit - it's whatever "feels" right when you try it out. Apple has an example here, where they don't specify a specific time either.

Answer 3

On Developer Forums on developer.apple.com, an Apple developer said:

• There's no constant time interval, but the system-wide definition is implicit today in the tapCount property of UITouch.
• There is not default value for this delay and for touch-and-hold delay.
• SpringBoard has the value hardcoded.

I have submitted this to Apple as bug 68405.

Answer 4

"- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

UITouch *touch = [touches anyObject];

NSUInteger tapCount = [touch tapCount];

switch (tapCount) {
    case 1:
        [self performSelector:@selector(singleTapMethod) withObject:nil afterDelay:.4];
        break;
    case 2:
        [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(singleTapMethod) object:nil];
        [self performSelector:@selector(doubleTapMethod) withObject:nil afterDelay:.4];
        break;
    case 3:
        [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(doubleTapMethod) object:nil];
        [self performSelector:@selector(tripleTapMethod) withObject:nil afterDelay:.4];
        break;
    case 4:
        [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(tripleTapMethod) object:nil];
        [self quadrupleTap];
        break;
    default:
        break;
}

} @end

for me this code is working prefectly fine.... :) the last post was around august 15 09.... but i was going through the same problem so thought to share the solution i found....

Answer 5

In the Apple provided example of the iPhone Application Programming Guide: Event Handling (mentioned by user Italy) a delay of 0.3 is used:

[self performSelector:@selector(handleSingleTap:) withObject:touchLoc afterDelay:0.3];