Gestures

Overview

Subjects

Using Gestures

Tags: #MagnificationGesture #onChanged #RotationGesture #rotationEffect

Magnification

struct ContentView: View {
    @State private var currentAmount = 0.0
    @State private var finalAmount = 1.0

    var body: some View {
        Text("Hello, World!")
            .scaleEffect(finalAmount + currentAmount)
            .gesture(
                MagnificationGesture()
                    .onChanged { amount in
                        currentAmount = amount - 1
                    }
                    .onEnded { amount in
                        finalAmount += currentAmount 
                        currentAmount = 0
                    }
            )
    }
}

Rotation

struct ContentView: View {
    @State private var currentAmount = Angle.zero
    @State private var finalAmount = Angle.zero

    var body: some View {
        Text("Hello, World!")
            .rotationEffect(currentAmount + finalAmount)
            .gesture(
                RotationGesture()
                    .onChanged { angle in
                        currentAmount = angle
                    }
                    .onEnded { angle in
                        finalAmount += currentAmount
                        currentAmount = .zero
                    }
            )
    }
}

Tapping

struct ContentView: View {
    var body: some View {
        VStack {
            Text("Hello, World!")
                .onTapGesture {
                    print("Text tapped")
                }
        }
        .onTapGesture {
            print("VStack tapped")
        }
    }
}

Dragging

Tags: #offset #DragGesture #CGSize #RotationEffect #removal #swipe

Tags: #Swipe #Drag #DifferentiateWithoutColor #xmark #checkmark

For colorblinds you may should use graphics instead of colors. Differentiate Without Color will help on this purpose.

High Priority Gesture

As default, SwiftUI gives priority to child gesture. To overcome that we should define the parent Gesture as a highpriority.

struct ContentView: View {
    var body: some View {
        VStack {
            Text("Hello, World!")
                .onTapGesture {
                    print("Text tapped")
                }
        }
        .highPriorityGesture(
            TapGesture()
                .onEnded { _ in
                    print("VStack tapped")
                }
        )
    }
}

Simultaneous Gesture

Trigers all the gestures at the same time.

struct ContentView: View {
    var body: some View {
        VStack {
            Text("Hello, World!")
                .onTapGesture {
                    print("Text tapped")
                }
        }
        .simultaneousGesture(
            TapGesture()
                .onEnded { _ in
                    print("VStack tapped")
                }
        )
    }
}

Sequential Gestures

First needs to be long pressed, an than it activates the second gesture.

struct ContentView: View {
    // how far the circle has been dragged
    @State private var offset = CGSize.zero

    // whether it is currently being dragged or not
    @State private var isDragging = false

    var body: some View {
        // a drag gesture that updates offset and isDragging as it moves around
        let dragGesture = DragGesture()
            .onChanged { value in offset = value.translation }
            .onEnded { _ in
                withAnimation {
                    offset = .zero
                    isDragging = false
                }
            }

        // a long press gesture that enables isDragging
        let pressGesture = LongPressGesture()
            .onEnded { value in
                withAnimation {
                    isDragging = true
                }
            }

        // a combined gesture that forces the user to long press then drag
        let combined = pressGesture.sequenced(before: dragGesture)

        // a 64x64 circle that scales up when it's dragged, sets its offset to whatever we had back from the drag gesture, and uses our combined gesture
        Circle()
            .fill(.red)
            .frame(width: 64, height: 64)
            .scaleEffect(isDragging ? 1.5 : 1)
            .offset(offset)
            .gesture(combined)
    }
}

Solutions / Examples

Dynamic Emoji

https://twitter.com/philipcdavis/status/1580211607627390976?s=12&t=PW_LE1rEl7C8W6gcTx0V3g

Swift Dev Notes