How to switch watch faces using swipe gestures

A welcome addition to WatchKit 3.0 is the swipe gesture recognizer.  Previously, I used an ordinary button to switch between modes in my Watch Face app, but now I can mimic the behaviour of official watch faces by swiping left or right.

The change is quite simple to make too. First, you just need a Group control that contains an image (into which you’ll draw the watch face). Then, you drag a couple of Swipe Gesture Recognizers into the group, and change the properties so that one is a left swipe and the other is a right swipe.

Having done that, you need to insert an action for each of the gestures – you can do that by control-dragging from the gesture in the storyboard outline into the InterfaceController code. Make sure to add an action (rather than an outlet) – that way, Xcode will create a stub method for you with the correct signature.

The logic for the swipe gesture just switches between watch faces then re-draws the time:

    // Tissot --> Hermes --> Roman
    @IBAction func swipeRight(_ sender: Any) {
        switch (watchFace.id())
        {
        case WatchFaceId.tissot: watchFace = HermesWatchFace()
        case WatchFaceId.hermes: watchFace = RomanWatchFace()
        case WatchFaceId.roman: watchFace = TissotWatchFace()
        }
        
        drawTime() // refresh with updated background & different styles
    }

and the left swipe reverses the transition order.

See also this earlier post that explains how you can draw directly into an image in WatchKit – combined with the swipe gesture recogniser, it provides a neat way to switch between different modes in any app.

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