Swift, swipe gesture recognizer direction doesn’t work, can’t seem to get the direction

Question

Edit: it seems the swipe gesture can only takes one direction a time now. If someone knows another way to handle multiple directions at once, I’d still appreciate information!

Eidt: I find a way to deal with multiple directions concisely in this [answer] (https://stackoverflow.com/a/46104997/9645644) It uses an array literal with forEach loop. It’s much more convenient than adding gestures and dragging actions separately from storyboard.

I’m trying to get swift swipe gestures to work, everything’s fine until I tried to detect the direction of the swipe. Below is my code. I don’t understand why this isn’t working and would appreciate help!

In a view controller’s viewDidLoad I set up and added the swipe gesture recognizer, with direction[.left, .right]. After that I implemented the handler method which needs to detect the direction of the swipe. There’s no other stuff in this view controller. After it failed to work(no response when swipe), I added a few prints, and got the output in the title.

override func viewDidLoad() {
    super.viewDidLoad()
    let swipeGestureRecognizer = UISwipeGestureRecognizer(target:self, action:#selector(swipeHandler(recognizer: )))
    swipeGestureRecognizer.direction = [.left, .right]
    view.addGestureRecognizer(swipeGestureRecognizer)
}

@objc func swipeHandler (recognizer: UISwipeGestureRecognizer){
    switch recognizer.state{
    case .ended:
        let direction = recognizer.direction
        print(direction)
        if direction == .left {print(”left”)}
        else if direction == .right {print(“right”)}
        else {print(print(“none”)}
    defaul: break
}

No matter left or right I swipe, it always prints “none”. And the direction print always give a “UISwipeGestureRecognizerDirection(rawValue: 3)”

FYI - when creating a swipe gesture, you are only supposed to set a single direction. Note the documentation states: *"The permitted direction"*. It does not state *"The permitted directions"*. — rmaddy, Jan 01 '19 at 16:24
I think it’s changed in swift 4 and now you can do multiple? I’ve seen others do it. — Antonia Zhang, Jan 01 '19 at 16:25
Okay I tried and it worked.Seems they did change it back... thanks! — Antonia Zhang, Jan 01 '19 at 16:44

score 1 · Answer 1 · answered Jan 01 '19 at 16:25

1

The direction property tells the gesture when to trigger. for example if direction == .right then the swipe will trigger only on a swipe to the right. (It does not tell you the direction detected)

answered Jan 01 '19 at 16:25

giorashc

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But then how do you detect a swipe? – Antonia Zhang Jan 01 '19 at 16:28
The same way you did. Once the gesture class detects a swipe in the selected direction it will trigger your callback method. I am not familiar with having multiple directions though. You can create a gesture for each direction and use the same callback method and distinguish the swipes by reading the direction property – giorashc Jan 01 '19 at 16:29
I try to detect it in the handler method by conditions, but it just doesn’t work, and it seems to always be the “else” case. – Antonia Zhang Jan 01 '19 at 16:32
1

try using only one direction. – giorashc Jan 01 '19 at 16:35
Okay I’ll try this. – Antonia Zhang Jan 01 '19 at 16:37
1

You’re right. It worked this time. I guess this means more code to write. Thank you! – Antonia Zhang Jan 01 '19 at 16:44

score 0 · Accepted Answer · answered Jan 01 '19 at 17:44

You need to detect one direction at a time. I would also suggest to add a method to control each swipe direction. For example.

func setUpGestures() {
    // Gesture that define a left swipe.
    let swipeLeft = UISwipeGestureRecognizer(target: self, action: #selector(Scene.swipeLeft))
    swipeLeft.direction = .left
    view?.addGestureRecognizer(swipeLeft)
    // Do the same for the rest of the directions.
}

@objc func swipeLeft() {
    // Do something when the user swipe left.
}

Hope it helps!

Swift, swipe gesture recognizer direction doesn’t work, can’t seem to get the direction

2 Answers2