How to make zoom in zoom out button animation on tap gesture in SwiftUI? - ios

Question

Simple and regular approach to animate a bump effect for a button but not simple in SwiftUI.
I'm trying to change scale in tapGesture modifier, but it doesn't have any effect. I don't know how to make chain of animations, probably because SwiftUI doesn't have it. So my naive approach was:
#State private var scaleValue = CGFloat(1)
...
Button(action: {
withAnimation {
self.scaleValue = 1.5
}
withAnimation {
self.scaleValue = 1.0
}
}) {
Image("button1")
.scaleEffect(self.scaleValue)
}
Obviously it doesn't work and buttons image get last scale value immediately.
My second thought was to change scale to 0.8 value on hold event and then after release event make scale to 1.2 and again after few mseconds change it to 1.0. I guess this algorithm should make nice and more natural bump effect. But I couldn't find suitable gesture struct in SwiftUI to handle hold-n-release event.
P.S. For ease understanding, I will describe the steps of the hold-n-release algorithm:
Scale value is 1.0
User touch the button
The button scale becomes 0.8
User release the button
The button scale becomes 1.2
Delay 0.1 sec
The button scale go back to default 1.0
UPD: I found a simple solution using animation delay modifier. But I'm not sure it's right and clear. Also it doens't cover hold-n-release issue:
#State private var scaleValue = CGFloat(1)
...
Button(action: {
withAnimation {
self.scaleValue = 1.5
}
//
// Using delay for second animation block
//
withAnimation(Animation.linear.delay(0.2)) {
self.scaleValue = 1.0
}
}) {
Image("button1")
.scaleEffect(self.scaleValue)
}
UPD 2:
I noticed in solution above it doesn't matter what value I pass as argument to delay modifier: 0.2 or 1000 will have same effect. Perhaps it's a bug 🐞
So I've used Timer instance instead of delay animation modifier. And now it's working as expected:
...
Button(action: {
withAnimation {
self.scaleValue = 1.5
}
//
// Replace it
//
// withAnimation(Animation.linear.delay(0.2)) {
// self.scaleValue = 1.0
// }
//
// by Timer with 0.5 msec delay
//
Timer.scheduledTimer(withTimeInterval: 0.5, repeats: false) { _ in
withAnimation {
self.scaleValue = 1.0
}
}
}) {
...
UPD 3:
Until we waiting official Apple update, one of suitable solution for realization of two events touchStart and touchEnd is based on #average Joe answer:
import SwiftUI
struct TouchGestureViewModifier: ViewModifier {
let minimumDistance: CGFloat
let touchBegan: () -> Void
let touchEnd: (Bool) -> Void
#State private var hasBegun = false
#State private var hasEnded = false
init(minimumDistance: CGFloat, touchBegan: #escaping () -> Void, touchEnd: #escaping (Bool) -> Void) {
self.minimumDistance = minimumDistance
self.touchBegan = touchBegan
self.touchEnd = touchEnd
}
private func isTooFar(_ translation: CGSize) -> Bool {
let distance = sqrt(pow(translation.width, 2) + pow(translation.height, 2))
return distance >= minimumDistance
}
func body(content: Content) -> some View {
content.gesture(DragGesture(minimumDistance: 0)
.onChanged { event in
guard !self.hasEnded else { return }
if self.hasBegun == false {
self.hasBegun = true
self.touchBegan()
} else if self.isTooFar(event.translation) {
self.hasEnded = true
self.touchEnd(false)
}
}
.onEnded { event in
if !self.hasEnded {
let success = !self.isTooFar(event.translation)
self.touchEnd(success)
}
self.hasBegun = false
self.hasEnded = false
}
)
}
}
extension View {
func onTouchGesture(minimumDistance: CGFloat = 20.0,
touchBegan: #escaping () -> Void,
touchEnd: #escaping (Bool) -> Void) -> some View {
modifier(TouchGestureViewModifier(minimumDistance: minimumDistance, touchBegan: touchBegan, touchEnd: touchEnd))
}
}

Answer 1

struct ScaleButtonStyle: ButtonStyle {
func makeBody(configuration: Self.Configuration) -> some View {
configuration.label
.scaleEffect(configuration.isPressed ? 2 : 1)
}
}
struct Test2View: View {
var body: some View {
Button(action: {}) {
Image("button1")
}.buttonStyle(ScaleButtonStyle())
}
}

Answer 2

Upgrading code for answer for iOS 15 (but this also available in iOS 13).
The one-parameter form of the animation() modifier has now been formally deprecated, mostly because it caused all sorts of unexpected behaviors (for ex in Lazy stacks: lazy(v/h)scroll, lazyvgrid): Button animated unexpectedly (jumping) during scrolling.
public struct ScaleButtonStyle: ButtonStyle {
public init() {}
public func makeBody(configuration: Self.Configuration) -> some View {
configuration.label
.scaleEffect(configuration.isPressed ? 0.95 : 1)
.animation(.linear(duration: 0.2), value: configuration.isPressed)
.brightness(configuration.isPressed ? -0.05 : 0)
}
}
public extension ButtonStyle where Self == ScaleButtonStyle {
static var scale: ScaleButtonStyle {
ScaleButtonStyle()
}
}

Answer 3

Yes, it looks like a bug but after my experimenting I found that you can do so
I've post a demo at https://youtu.be/kw4EIOCp78g
struct TestView: View {
#State private var scaleValue = CGFloat(1)
var body: some View {
ZStack {
CustomButton(
touchBegan: {
withAnimation {
self.scaleValue = 2
}
},
touchEnd: {
withAnimation {
self.scaleValue = 1
}
}
){
Image("button1")
}.frame(width: 100, height: 100)
Image("button1").opacity(scaleValue > 1 ? 1 : 0).scaleEffect(self.scaleValue)
}
}
}
struct CustomButton<Content: View>: UIViewControllerRepresentable {
var content: Content
var touchBegan: () -> ()
var touchEnd: () -> ()
typealias UIViewControllerType = CustomButtonController<Content>
init(touchBegan: #escaping () -> (), touchEnd: #escaping () -> (), #ViewBuilder content: #escaping () -> Content) {
self.touchBegan = touchBegan
self.touchEnd = touchEnd
self.content = content()
}
func makeUIViewController(context: Context) -> UIViewControllerType {
CustomButtonController(rootView: self.content, touchBegan: touchBegan, touchEnd: touchEnd)
}
func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {
}
}
class CustomButtonController<Content: View>: UIHostingController<Content> {
var touchBegan: () -> ()
var touchEnd: () -> ()
init(rootView: Content, touchBegan: #escaping () -> (), touchEnd: #escaping () -> ()) {
self.touchBegan = touchBegan
self.touchEnd = touchEnd
super.init(rootView: rootView)
self.view.isMultipleTouchEnabled = true
}
#objc required dynamic init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesBegan(touches, with: event)
self.touchBegan()
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesCancelled(touches, with: event)
self.touchEnd()
}
//touchesEnded only works if the user moves his finger beyond the bound of the image and releases
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesEnded(touches, with: event)
self.touchEnd()
}
}
There is another strange thing if we move and scale the second Image to the first then it will not be shown without .frame(width: 100, height: 100).

Answer 4

Nice and clean swiftUI solution:
#State private var scaleValue = CGFloat(1)
...
Image("button1")
.scaleEffect(self.scaleValue)
.onTouchGesture(
touchBegan: { withAnimation { self.scaleValue = 1.5 } },
touchEnd: { _ in withAnimation { self.scaleValue = 1.0 } }
)
however, you also need to add this code snippet to the project:
struct TouchGestureViewModifier: ViewModifier {
let touchBegan: () -> Void
let touchEnd: (Bool) -> Void
#State private var hasBegun = false
#State private var hasEnded = false
private func isTooFar(_ translation: CGSize) -> Bool {
let distance = sqrt(pow(translation.width, 2) + pow(translation.height, 2))
return distance >= 20.0
}
func body(content: Content) -> some View {
content.gesture(DragGesture(minimumDistance: 0)
.onChanged { event in
guard !self.hasEnded else { return }
if self.hasBegun == false {
self.hasBegun = true
self.touchBegan()
} else if self.isTooFar(event.translation) {
self.hasEnded = true
self.touchEnd(false)
}
}
.onEnded { event in
if !self.hasEnded {
let success = !self.isTooFar(event.translation)
self.touchEnd(success)
}
self.hasBegun = false
self.hasEnded = false
})
}
}
extension View {
func onTouchGesture(touchBegan: #escaping () -> Void,
touchEnd: #escaping (Bool) -> Void) -> some View {
modifier(TouchGestureViewModifier(touchBegan: touchBegan, touchEnd: touchEnd))
}
}

Answer 5

Ok, I think I might have a decent solution here. GIST here
I've put together a bunch of things to make this work. First, a AnimatableModifier that observes if an animation has ended. All thanks to avanderlee
/// An animatable modifier that is used for observing animations for a given animatable value.
public struct AnimationCompletionObserverModifier<Value>: AnimatableModifier where Value: VectorArithmetic {
/// While animating, SwiftUI changes the old input value to the new target value using this property. This value is set to the old value until the animation completes.
public var animatableData: Value {
didSet {
notifyCompletionIfFinished()
}
}
/// The target value for which we're observing. This value is directly set once the animation starts. During animation, `animatableData` will hold the oldValue and is only updated to the target value once the animation completes.
private var targetValue: Value
/// The completion callback which is called once the animation completes.
private var completion: () -> Void
init(observedValue: Value, completion: #escaping () -> Void) {
self.completion = completion
self.animatableData = observedValue
targetValue = observedValue
}
/// Verifies whether the current animation is finished and calls the completion callback if true.
private func notifyCompletionIfFinished() {
guard animatableData == targetValue else { return }
/// Dispatching is needed to take the next runloop for the completion callback.
/// This prevents errors like "Modifying state during view update, this will cause undefined behavior."
DispatchQueue.main.async {
self.completion()
}
}
public func body(content: Content) -> some View {
/// We're not really modifying the view so we can directly return the original input value.
return content
}
}
public extension View {
/// Calls the completion handler whenever an animation on the given value completes.
/// - Parameters:
/// - value: The value to observe for animations.
/// - completion: The completion callback to call once the animation completes.
/// - Returns: A modified `View` instance with the observer attached.
func onAnimationCompleted<Value: VectorArithmetic>(for value: Value, completion: #escaping () -> Void) -> ModifiedContent<Self, AnimationCompletionObserverModifier<Value>> {
return modifier(AnimationCompletionObserverModifier(observedValue: value, completion: completion))
}
}
Now that we can track the end of a animation, another view modifer takes care of tracking the end of the zoom out animation and starts a new zoom in animation using a bunch of booleans to track the animation state. Forgive the naming.
struct ZoomInOutOnTapModifier: ViewModifier {
var destinationScaleFactor: CGFloat
var duration: TimeInterval
init(duration: TimeInterval = 0.3,
destinationScaleFactor: CGFloat = 1.2) {
self.duration = duration
self.destinationScaleFactor = destinationScaleFactor
}
#State var scale: CGFloat = 1
#State var secondHalfAnimationStarted = false
#State var animationCompleted = false
func body(content: Content) -> some View {
content
.scaleEffect(scale)
.simultaneousGesture(DragGesture(minimumDistance: 0.0, coordinateSpace: .global)
.onChanged({ _ in
animationCompleted = true
withAnimation(.linear(duration: duration)) {
scale = destinationScaleFactor
}
})
.onEnded({ _ in
withAnimation(.linear(duration: duration)) {
scale = 1
}
secondHalfAnimationStarted = true
})
)
.onAnimationCompleted(for: scale) {
if scale == 1 {
secondHalfAnimationStarted = false
animationCompleted = true } else if scale == destinationScaleFactor {
animationCompleted = false
secondHalfAnimationStarted = true
}
if !secondHalfAnimationStarted {
withAnimation(.linear(duration: duration)) {
scale = 1
}
}
}
}
}
public extension View {
func addingZoomOnTap(duration: TimeInterval = 0.3, destinationScaleFactor: CGFloat = 1.2) -> some View {
modifier(ZoomInOutOnTapModifier(duration: duration, destinationScaleFactor: destinationScaleFactor))
}
}
All put together:
PlaygroundPage.current.setLiveView(
Button {
print("Button tapped")
} label: {
Text("Tap me")
.font(.system(size: 20))
.foregroundColor(.white)
.padding()
.background(Capsule()
.fill(Color.black))
}
.addingZoomOnTap()
.frame(width: 300, height: 300)
)
Let me know if improvements can be made.
EDIT:
In case you want the button to be in the scaled state until the user lets go(touchUp) of the button, the ViewModifier become much simpler.
struct ZoomInOutOnTapModifier: ViewModifier {
var destinationScaleFactor: CGFloat
var duration: TimeInterval
init(duration: TimeInterval = 0.3,
destinationScaleFactor: CGFloat = 1.2) {
self.duration = duration
self.destinationScaleFactor = destinationScaleFactor
}
#State var scale: CGFloat = 1
func body(content: Content) -> some View {
content
.scaleEffect(scale)
.simultaneousGesture(DragGesture(minimumDistance: 0.0, coordinateSpace: .global)
.onChanged({ _ in
withAnimation(.linear(duration: duration)) {
scale = destinationScaleFactor
}
})
.onEnded({ _ in
withAnimation(.linear(duration: duration)) {
scale = 1
}
})
)
}
}