CODEWITHSUNDEEP
macosswiftuidraggesture
Chris
Chris

Reputation: 8432

SwiftUI DragGesture inconsistencies with location and start location

I'm building a SwiftUI macOS app.

I've got a basic Rectangle shape with a drag gesture on it.

In the onEnded handler, I am wanting to determine if the user has effectively tapped on the object. I do this by checking that the width and height of the translation are both zero.

(There are reasons I'm not using a tap gesture).

Rectangle()
    .size(.init(width:50, height: 50))
    .fill(Color.blue.opacity(0.01))
    .gesture(DragGesture(minimumDistance:0)
                .onChanged { gesture in
                    // Ommited
                }
                .onEnded { gesture in
                    print("startLocation", gesture.startLocation)
                    print("start", gesture.location)
                    print("translation", gesture.translation)
                    
                    if gesture.translation == .zero {
                        print("tap")
                    }

                    print()
                }
    )

I'm getting issues where translations are being reported with unexpected values.

The values reported differ based on where I click in the rectangle.

Here's a set of groups of individual clicks. The translation is derived from the startLocation and location fields.

You can see variation between the startLocation and the location fields. If it was a very small variation I could debounce, however the fact that sometimes I get a value of 3 makes me wonder why such a variation could happen (I'm being over the top careful to execute the click without movement).

Does anyone know why this variation is creeping in?

startLocation (263.5149841308594, 144.3092803955078)
start (263.51495361328125, 144.30926513671875)
translation (-3.0517578125e-05, -1.52587890625e-05)

startLocation (276.2882995605469, 144.43479919433594)
start (276.288330078125, 144.434814453125)
translation (3.0517578125e-05, 1.52587890625e-05)

startLocation (274.3827209472656, 162.3402557373047)
start (274.38275146484375, 162.34027099609375)
translation (3.0517578125e-05, 1.52587890625e-05)

startLocation (264.81805419921875, 167.47662353515625)
start (264.81805419921875, 167.47662353515625)
translation (0.0, 0.0)
tap

startLocation (254.5931396484375, 135.4690399169922)
start (254.5931396484375, 135.46905517578125)
translation (0.0, 1.52587890625e-05)

startLocation (259.1647033691406, 140.26919555664062)
start (259.16473388671875, 140.26919555664062)
translation (3.0517578125e-05, 0.0)

Edit

As pointed out below, the value of 3 is actually 3e-05 = 0.00003 which I missed at the time of writing. However, still looking for information as to why the tap gesture will have zero translation on repeated clicks in some points of the Rectangle, but have a non zero translation in others.

Upvotes: 1

Views: 798

Answers (1)

Taeeun Kim
Taeeun Kim

Reputation: 1256

How about this?

if gesture.translation.width/UIScreen.main.bounds.width < 0.05 &&
gesture.translation.height/UIScreen.main.bounds.height < 0.05 
{
    print("tap") // 0.01 ~ 0.05
}

This way works, regardless of the size of the device and width & height, it is always constant as it falls in percentages.

Upvotes: 0

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