Dismiss modal view form sheet controller on outside tap

I solved iOS 8 issue by adding delegate to gesture recognizer

[taprecognizer setDelegate:self];

with these responses

#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;
}

that works for me with iOS 8 GM

I know this is an old question but this IS possible, despite of what the "right" answer says. Since this was the first result when I was looking for this I decided to elaborate:

This is how you do it:

You need to add a property to the View Controller from where you want to present modally, in my case "tapBehindGesture".

then in viewDidAppear

if(!tapBehindGesture) {
        tapBehindGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapBehindDetected:)];
        [tapBehindGesture setNumberOfTapsRequired:1];
        [tapBehindGesture setCancelsTouchesInView:NO]; //So the user can still interact with controls in the modal view
    }

[self.view.window addGestureRecognizer:tapBehindGesture];

And Here is the implementation for tapBehindDetected

- (void)tapBehindDetected:(UITapGestureRecognizer *)sender
{

    if (sender.state == UIGestureRecognizerStateEnded)
    {
        //(edited) not working for ios8 above 
        //CGPoint location = [sender locationInView:nil]; //Passing nil gives us coordinates in the window

        CGPoint location = [sender locationInView: self.presentingViewController.view];

        //Convert tap location into the local view's coordinate system. If outside, dismiss the view.
        if (![self.presentedViewController.view pointInside:[self.presentedViewController.view convertPoint:location fromView:self.view.window] withEvent:nil])
        {   
            if(self.presentedViewController) {
                [self dismissViewControllerAnimated:YES completion:nil];
            }
        }
    }
}

Just remember to remove tapBehindGesture from view.window on viewWillDisappear to avoid triggering handleTapBehind in an unallocated object.