iOS UIGestureRecognizer UIPanGestureRecognizer
Example
Pan gesture recognizers detect dragging gestures. The following example adds an image to a view controller and lets the user drag it around on screen.
Objective-C
- (void)viewDidLoad {
[super viewDidLoad];
UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"imageToDrag"]];
[imageView sizeToFit];
imageView.userInteractionEnabled = YES;
[self.view addSubview:imageView];
UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
[imageView addGestureRecognizer:pan];
}
- (void)handlePan:(UIPanGestureRecognizer *)recognizer {
CGPoint translation = [recognizer translationInView:self.view];
recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
recognizer.view.center.y + translation.y);
[recognizer setTranslation:CGPointZero inView:self.view];
}
Swift
override func viewDidLoad() {
super.viewDidLoad()
let imageView = UIImageView.init(image: UIImage.init(named: "imageToDrag"))
imageView.sizeToFit()
imageView.isUserInteractionEnabled = true
self.view.addSubview(imageView)
let pan = UIPanGestureRecognizer.init(target: self, action: #selector(handlePan(recognizer:)))
imageView.addGestureRecognizer(pan)
}
func handlePan(recognizer: UIPanGestureRecognizer) {
let translation = recognizer.translation(in: self.view)
if let view = recognizer.view {
view.center = CGPoint(x: view.center.x + translation.x, y: view.center.y + translation.y)
}
recognizer.setTranslation(CGPoint.zero, in: self.view)
}
Note: Although
UIPanGestureRecognizeris useful for detecting any dragging gestures, if you just want to detect a basic gesture such as user dragging their finger left/right or up/down, useUISwipeGestureRecognizer.UIPanGestureRecognizeris a better choice if you need access to methods such astranslationInView:orvelocityInView:.
