Two fingered swipe v. one fingered drag in iOS

In my app I have a UIView deriv开发者_JS百科ed class Canvas that uses touchesBegan: withEvent:, touchesMoved: withEvent:, and touchesEnded: withEvent: to draw in the canvas. I also want to use a swipe to load the previous (or next) canvas in an array. I tried setting up the following gesture (and a similar one for right):

UISwipeGestureRecognizer* leftSwipe = [[UISwipeGestureRecognizer alloc] initWithTarget: self action: @selector(pageFlipNext)];
leftSwipe.direction = UISwipeGestureRecognizerDirectionLeft;
leftSwipe.numberOfTouchesRequired = 2;
[_canvas addGestureRecognizer: leftSwipe];
[leftSwipe release];

But my two fingered swipes are still being treated as one-fingered drawing instructions. How do I get my app to handle the two-fingered swipe correctly?

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First of all, I would get started verifying whether _canvas.multipleTouchEnabled is set to YES. If it isn't, set it to YES.

You might also want to consider

leftSwipe.delaysTouchesBegan = YES;

This will delay the touches to be sent to the _canvas until the gesture fails. You can also use a UIPanGestureRecognizer and do something like this,

[pan requireGestureRecognizerToFail:leftSwipe];

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I think that you can use UIPanGestureRecognizer

UIPanGestureRecognizer is a concrete subclass of UIGestureRecognizer that looks for panning (dragging) gestures. The user must be pressing one or more fingers on a view while they pan it.