How to disable multitouch?

If you want only one button to respond to touches at a time, you need to set exclusiveTouch for that button, rather than for the parent view. Alternatively, you could disable the other buttons when a button gets the "Touch Down" event.

Here's an example of the latter, which worked better in my testing. Setting exclusiveTouch for the buttons kind-of worked, but led to some interesting problems when you moved your finger off the edge of a button, rather than just clicking it.

You need to have outlets in your controller hooked up to each button, and have the "Touch Down", "Touch Up Inside", and "Touch Up Outside" events hooked to the proper methods in your controller.

#import "multibuttonsViewController.h"

@implementation multibuttonsViewController

// hook this up to "Touch Down" for each button
- (IBAction) pressed: (id) sender
{
    if (sender == one)
    {
        two.enabled = false;
        three.enabled = false;
        [label setText: @"One"]; // or whatever you want to do
    }
    else if (sender == two)
    {
        one.enabled = false;
        three.enabled = false;
        [label setText: @"Two"];  // or whatever you want to do
    }
    else
    {
        one.enabled = false;
        two.enabled = false;
        [label setText: @"Three"];  // or whatever you want to do
    }
}

// hook this up to "Touch Up Inside" and "Touch Up Outside"
- (IBAction) released: (id) sender
{
    one.enabled = true;
    two.enabled = true;
    three.enabled = true;
}

@end

- (void)viewDidLoad {
    [super viewDidLoad];

    for(UIView* v in self.view.subviews)
    {
        if([v isKindOfClass:[UIButton class]])
        {
            UIButton* btn = (UIButton*)v;
            [btn setExclusiveTouch:YES];
        }
    }
}

This code is tested and working perfectly for me.there is no app crash when pressing more than one button at a time.

Your app crashes for a reason. Investigate further, use the debugger, see what's wrong instead of trying to hide the bug.

Edit:

OK, ok, I have to admit I was a bit harsh. You have to set the exclusiveTouch property on each button. That's all. The multipleTouchEnabled property is irrelevant.

For disabling global multitouch in Xamarin.iOS

Copy&Paste the code below:

[DllImport(ObjCRuntime.Constants.ObjectiveCLibrary, EntryPoint = "objc_msgSend")]
internal extern static IntPtr IntPtr_objc_msgSend(IntPtr receiver, IntPtr selector, bool isExclusiveTouch);
static void SetExclusiveTouch(bool isExclusiveTouch)
{
    var selector = new ObjCRuntime.Selector("setExclusiveTouch:");
    IntPtr_objc_msgSend(UIView.Appearance.Handle, selector.Handle, isExclusiveTouch);
}

And set it on AppDelegate:

public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
    ...
    SetExclusiveTouch(true); // setting exlusive to true disables the multitouch
    ...
}

My experience is that, by default, a new project doesn't even allow multitouch, you have to turn it on. But I suppose that depends on how you got started. Did you use a mutlitouch example as a template?

First of all, are you absolutely sure multitouch is on? It's possible to generate single touches in sequence pretty quickly. Multitouch is more about what you do with two or more fingers once they are on the surface. Perhaps you have single touch on but aren't correctly dealing with what happens if two buttons are pressed at nearly the same time.

A Gotcha:

If you are using isExclusiveTouch, be aware that overriding point(inside:) on the button can interfere, effectively making isExclusiveTouch useless.

(Sometimes you need to override point(inside:) for handling the "button not responsive at bottom of iPhone screen" bug/misfeature (which is caused by Apple installing swipe GestureRecognizers at the bottom of the screen, interfering with button highlighting.)

See: UIButton fails to properly register touch in bottom region of iPhone screen