Is there a way to find out the maximum number of simultaneous touches on an iOS device (iPhone, iPod Touch, iPad) ? I've read here and there that iPhone can handle 5 while the iPad can handle 11, but I haven't found an official way (through a function call, say) to confirm this.
By testing it! See here for videos and source: http://mattgemmell.com/2010/05/09/ipad-multi-touch
There's no public API to request that information from the hardware.
iPhone can register 5 touch points on its tiny display, don't know about iPad.
Having said that, I wouldn't count on the numbers that you find empirically, because this information is not documented nor there is an api for it.
One good reason I can think of is the reduced touch sensor accuracy as the number of touch points increase.
来源：https://stackoverflow.com/questions/3149868/determining-the-maximum-number-of-simultaneous-touches-possible-on-an-ios-device