CODEWITHSUNDEEP
iosobjective-cuigesturerecognizer
Yacob Madiana
Yacob Madiana

Reputation: 13

Detect left and right movement using UILongPressGestureRecognizer?

From what I already know from this question Detecting the direction of PAN gesture in iOS answered by H2CO3, you can detect left or right movement in UIPanGestureRecognizer by using:

CGPoint vel = [gesture velocityInView:self.view];
if (vel.x > 0)
 {
     // user dragged towards the right
 }
 else
 {
     // user dragged towards the left
 }

I want to detect left or right movement when user tap and hold a button similar to code above by using UILongPressGestureRecognizer when user entered UIGestureRecognizerStateChanged state, but it seems I can't simply using velocityInView to make things work in my case.

Anyone can help me?

Upvotes: 1

Views: 1833

Answers (1)

Khanh Nguyen
Khanh Nguyen

Reputation: 11132

First set the recognizer's allowableMovement to a big value (it's 10 pixels by default). And use the following code

-(void)longPressed:(UILongPressGestureRecognizer*)g
{
    if (g.state == UIGestureRecognizerStateBegan) {
        _initial = [g locationInView:self.view]; // _initial is instance var of type CGPoint
    }
    else if (g.state == UIGestureRecognizerStateChanged)
    {
        CGPoint p = [g locationInView:self.view];
        double dx = p.x - _initial.x;
        if (dx > 0) {
            NSLog(@"Finger moved to the right");
        }
        else {
            NSLog(@"Finger moved to the left");
        }
    }
}

Note that UILongPressGestureRecognizer is continuous, so you'll receive multiples UIGestureRecognizerStateChanged. Use UIGestureRecognizerStateEnded if you only want one notification when the user lifted his finger.

Upvotes: 6

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