Iphone SDK dismissing Modal ViewControllers on ipad by clicking outside of it

I'm a year late, but this is pretty straightforward to do.

Have your modal view controller attach a gesture recognizer to the view's window:

UITapGestureRecognizer *recognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapBehind:)];

[recognizer setNumberOfTapsRequired:1];
recognizer.cancelsTouchesInView = NO; //So the user can still interact with controls in the modal view
[self.view.window addGestureRecognizer:recognizer];
[recognizer release];

The handling code:

- (void)handleTapBehind:(UITapGestureRecognizer *)sender
{
    if (sender.state == UIGestureRecognizerStateEnded)
     {
       CGPoint location = [sender locationInView:nil]; //Passing nil gives us coordinates in the window

 //Then we convert the tap's location into the local view's coordinate system, and test to see if it's in or outside. If outside, dismiss the view.

        if (![self.view pointInside:[self.view convertPoint:location fromView:self.view.window] withEvent:nil]) 
        {
           // Remove the recognizer first so it's view.window is valid.
          [self.view.window removeGestureRecognizer:sender];
          [self dismissModalViewControllerAnimated:YES];
        }
     }
}

That's about it. HIG be damned, this is a useful and often intuitive behavior.

For iOS 8, you must both implement the UIGestureRecognizer, and swap the (x,y) coordinates of the tapped location when in landscape orientation. Not sure if this is due to an iOS 8 bug.

- (void) viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    // add gesture recognizer to window

    UITapGestureRecognizer *recognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapBehind:)];
    [recognizer setNumberOfTapsRequired:1];
    recognizer.cancelsTouchesInView = NO; //So the user can still interact with controls in the modal view
    [self.view.window addGestureRecognizer:recognizer];
    recognizer.delegate = self;
}

- (void)handleTapBehind:(UITapGestureRecognizer *)sender
{
    if (sender.state == UIGestureRecognizerStateEnded) {

        // passing nil gives us coordinates in the window
        CGPoint location = [sender locationInView:nil];

        // swap (x,y) on iOS 8 in landscape
        if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")) {
            if (UIInterfaceOrientationIsLandscape([UIApplication sharedApplication].statusBarOrientation)) {
                location = CGPointMake(location.y, location.x);
            }
        }

        // convert the tap's location into the local view's coordinate system, and test to see if it's in or outside. If outside, dismiss the view.
        if (![self.view pointInside:[self.view convertPoint:location fromView:self.view.window] withEvent:nil]) {

            // remove the recognizer first so it's view.window is valid
            [self.view.window removeGestureRecognizer:sender];
            [self dismissViewControllerAnimated:YES completion:nil];
        }
    }
}


#pragma mark - UIGestureRecognizer Delegate

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    return YES;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    return YES;
}

The other apps are not using Modal Views if they allow the view to be dismissed by clicking outside of it. UIModalPresentationFormSheets cannot be dismissed this way. (nor, indeed can any UIModal in SDK3.2). Only the UIPopoverController can be dismissed by clicking outside of the area. It is very possible (though against Apple's iPad HIG) for the app developer to have shaded out the background screen and then displayed the UIPopoverController so that it looks like a UIModalPresentationFormSheets (or other UIModal View).

[...] UIModalPresentationCurrentContext style lets a view controller adopt the presentation style of its parent. In each modal view, the dimmed areas show the underlying content but do not allow taps in that content. Therefore, unlike a popover, your modal views must still have controls that allow the user to dismiss the modal view.

See the iPadProgrammingGuide on the developer site for more information (Page 46 -- "Configuring the Presentation Style for Modal Views")

The code above works great, but I would change the if statement to,

    if (!([self.view pointInside:[self.view convertPoint:location fromView:self.view.window] withEvent:nil] || [self.navigationController.view pointInside:[self.navigationController.view convertPoint:location fromView:self.navigationController.view.window] withEvent:nil]))

    {
        // Remove the recognizer first so it's view.window is valid.
        [self.view.window removeGestureRecognizer:sender];
        [self dismissModalViewControllerAnimated:YES];
    }

This makes sure you can still interact with the navigation bar, otherwise tapping in it dismisses the modal view.