UIScreenEdgePanGestureRecognizer Run multiple times

Question

I have the following code in viewDidLoad on a UIViewController:

UIScreenEdgePanGestureRecognizer *edgeRecognizer = [[UIScreenEdgePanGestureRecognizer alloc] initWithTarget:self action:@selector(handleRightEdgeSwipe:)]; edgeRecognizer.edges = UIRectEdgeRight; [self.view addGestureRecognizer:edgeRecognizer]; 

and the goal is to trigger a slide show when a right edge gesture is detected.

 -(void)handleRightEdgeSwipe:(UIGestureRecognizer*)sender { NSLog(@"Showing Side Bar"); [self presentPanelViewController:_lightPanelViewController withDirection:MCPanelAnimationDirectionRight]; } 

But I see that the handleRightEdgeSwipe function is run several times - sometimes 5 times, which makes the sidebar view, which should smoothly animate the slide in Flash several times.

(NOTE: I tried to start the view from UIButton and it works fine).

Why is the right edge gesture triggered several times and how can I fix it?

Answer 1

As noted, UIScreenEdgePanGestureRecognizer calls your action several times as the state of the GestureRecognizer changes. See the documentation for the state property of the UIGestureRecognizer class. So, in your case, I believe that the answer you are looking for is to check if the state has ended. Thus:

 -(void)handleRightEdgeSwipe:(UIGestureRecognizer*)sender { if (sender.state == UIGestureRecognizerStateEnded) { NSLog(@"Showing Side Bar"); [self presentPanelViewController:_lightPanelViewController withDirection:MCPanelAnimationDirectionRight]; } } 

Answer 2

This gesture is not a one-shot event, but continuous.

handleRightEdgeSwipe: called once when sender.state changes or the touch moves. You must move the UIButton depending on the state gesture and locationInView: