iOS - detect when more than one finger is on the screen

Question

I'm looking for the best way to detect more than one finger on the screen at time. I'm not detecting taps or pinching, just the fact that more than one touch is happening. There don't seem to be any gesture recognizers for that. What's the best way?

Answer 1

In the touchesBegan, touchesMoved, and touchesEnded methods, one parameter is event, which is a UIEvent object. The number of fingers on the screen is [[event allTouches]count].

[EDITED because Josh Hinman pointed out that I had it wrong before -- my previous suggestion of using [touches count] on the touches parameter in those same methods will not work.]

Answer 2

Read up on the -touchesBegan:withEvent: method. It's the entry point into multi-touch event handling.

Here's a developer's lib link on multitouch events: https://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/MultitouchEvents/MultitouchEvents.html

Answer 3

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

  NSLog(@"%lu",[[event allTouches] count]); }