Unexpected animation stack behavior on View - animation

The documentation says
.animation(, value:) Applies the given animation to this view when the specified value
changes.
When I have stack animations stack on my view, it is understandable that animation modifier animates all changed until its line after modifier changes shouldn't animate, that's fine until two animations.
When I add the third animation on the stack, this third change is affected by the first animation which is commented as below.
Is there any explanation for that? Am I missing something or this is a bug?
struct ContentView: View {
// MARK: Properties
#State private var half = false
#State private var dim = false
#State private var isBlack = false
#State private var isRotated = false
// MARK: View
var body: some View {
Image(systemName: "trash.fill")
.resizable()
.scaledToFit()
.rotationEffect(isRotated ? .degrees(180) : .degrees(0))
.opacity(dim ? 0.2 : 1.0)
.animation(.easeInOut(duration: 1.0), value: dim) // animates half, isblack and isRotated
.scaleEffect(half ? 0.5 : 1.0)
.animation(.easeInOut(duration: 5.0), value: half) // animates only half
.foregroundColor(isBlack ? .black : .blue)
.animation(.easeInOut(duration: 15.0).delay(5), value: isBlack) // doesnt have any effect
.onTapGesture {
dim.toggle()
half.toggle()
isBlack.toggle()
isRotated.toggle()
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}

Related

animation 'has been deprecated in iOS 15.0: use instead with Animation or animation (_: value :)

I apply ".animation (.easeIn)" but it is deprecated.
tells me: animation 'has been deprecated in iOS 15.0: use instead with Animation or animation (: value :), but animation (: value :) I don't know which value I need to pass. I can't create animations that start slowly. Can you please help me understand how I can properly use animation (_: value :) to make animation work? I have to create the animation that when I move the slider, the images slowly recompose in space according to how much they are enlarged or reduced.
thank you.
'''
import SwiftUI
struct GalleryView: View {
// MARK: - PROPERTIES
#State private var selectedAnimal: String = "lion"
let animals: [Animal] = Bundle.main.decode("animals.json")
let haptics = UIImpactFeedbackGenerator(style: .medium)
#State private var gridLayout: [GridItem] = [GridItem(.flexible())]
#State private var gridColumn: Double = 3.0
func gridSwitch() {
gridLayout = Array(repeating: .init(.flexible()), count: Int(gridColumn))
}
// MARK: - BODY
var body: some View {
ScrollView(.vertical, showsIndicators: false) {
VStack(alignment: .center, spacing: 30) {
// MARK: - IMAGE
Image(selectedAnimal)
.resizable()
.scaledToFit()
.clipShape(Circle())
.overlay(Circle().stroke(Color.white, lineWidth: 8))
// MARK: - SLIDER
Slider(value: $gridColumn, in: 2...4, step: 1) // se aumento il valore nello slider ci saranno piĆ¹ sezioni
.padding(.horizontal)
.onChange(of: gridColumn, perform: { value in
gridSwitch()
})
// MARK: - GRID
LazyVGrid(columns: gridLayout, alignment: .center, spacing: 10) {
ForEach(animals) { item in
Image(item.image)
.resizable()
.scaledToFit()
.clipShape(Circle())
.overlay(Circle().stroke(Color.white, lineWidth: 1))
.onTapGesture {
selectedAnimal = item.image
haptics.impactOccurred()
}
} //: LOOP
} //: GRID
.animation(.easeIn)
.onAppear(perform: {
gridSwitch()
})
} //: VSTACK
.padding(.horizontal, 10)
.padding(.vertical,50)
} //: SCROLL
.frame(maxWidth: .infinity, maxHeight: .infinity)
.background(MotionAnimationView())
}
}
// MARK: - PREVIEW
struct GalleryView_Previews: PreviewProvider {
static var previews: some View {
GalleryView()
}
}
As the error says, .animation() is deprecated, with iOS 15, you need to use .animation(value:) now. where the value is the binding that you want your animation to be triggered, in your case, I assume it is selectedAnimal.
Applying this would be something like
VStack {
}
.animation(.easeIn, value: selectedAnimal)
As discussed in comments, if you want your gridLayout to be animatable, it is a little bit more tricky. Because Arrays has to be Equatable if you want them to be animatable, since extending the GridItem is not a good solution, I came up with this:
delete your .animation method change your gridSwitch function with this:
struct GalleryView: View {
// ... irrelevant code
#State private var isGridChanged = false
func gridSwitch() {
if (isGridChanged) {
withAnimation {
gridLayout = Array(repeating: .init(.flexible()), count: Int(gridColumn))
}
}
else {
gridLayout = Array(repeating: .init(.flexible()), count: Int(gridColumn))
isGridChanged = true
}
}
isGridChanged is required because as you're changing your gridLayout when your View is initialized, it causes a weird bug that everything is getting scaled down when app launches because of withAnimation.

SwiftUI: Animated rotation in different sides

At first look question can seen ordinary but after spend few hour try out different techniques I still failed to achieve expected behavior... I want to control the rotation side of View depending in #State. If view in default position (chevron up) it should rotate down from the right side. If chevron is down it should rotate up from the left side.
And one more thing I discovered: in my work project I use Image instead SF Symbol with the same modification like in code example and by default it always rotates from the right side, but using SF Symbol it's going from left. I will be grateful if you explain why
struct Arrow: View {
#State var showView = false
var body: some View {
VStack {
Image(systemName: "chevron.up.circle")
.resizable()
.frame(width: 50, height: 50)
.rotationEffect(.degrees(showView ? 180 : 360))
.animation(Animation.easeInOut(duration: 0.3), value: showView)
}
.onTapGesture { showView.toggle() }
}
}
To always rotate in the same direction, maintain a rotationAngle that always increases (or always decreases) while animating:
struct ContentView: View {
#State private var showView = false
#State private var rotationAngle: Double = 0
var body: some View {
VStack {
Image(systemName: "chevron.up.circle")
.resizable()
.frame(width: 50, height: 50)
.rotationEffect(Angle(degrees: rotationAngle))
}
.onTapGesture {
showView.toggle()
withAnimation(.easeInOut(duration: 0.3)) {
rotationAngle += 180
}
rotationAngle = showView ? 180 : 0
}
}
}
Note: Use rotationAngle -= 180 to rotate in the other direction.

SwiftUI transition with opacity not showing

I'm still new to SwiftUI. I'm trying to get each change of an image to start out at opacity 0.0 (fully transparent), then increase to opacity 1.0 (fully opaque)
I expected I could achieve this using the .opacity transition. .opacity is described as a "transition from transparent to opaque on insertion", so my assumption is that by stating "withAnimation" in my Button action, I'd trigger the Image to be re-rendered, and the transition would occur beginning from faded to transparent. Instead I see the same instant appear of the new shape & slow morphing to a new size, no apparent change in .opacity. Code and .gif showing current result, below. I've used UIKit & know I'd set alpha to zero, then UIView.animate to alpha 1.0 over a duration of 1.0, but am unsure how to get the same effect in SwiftUI. Thanks!
struct ContentView: View {
#State var imageName = ""
var imageNames = ["applelogo", "peacesign", "heart", "lightbulb"]
#State var currentImage = -1
var body: some View {
VStack {
Spacer()
Image(systemName: imageName)
.resizable()
.scaledToFit()
.padding()
.transition(.opacity)
Spacer()
Button("Press Me") {
currentImage = (currentImage == imageNames.count - 1 ? 0 : currentImage + 1)
withAnimation(.linear(duration: 1.0)) {
imageName = imageNames[currentImage]
}
}
}
}
}
The reason you are not getting the opacity transition is that you are keeping the same view. Even though it is drawing a different image each time, SwiftUI sees Image as the same. the fix is simple: add .id(). For example:
Image(systemName: imageName)
.resizable()
.scaledToFit()
.padding()
.transition(.opacity)
// Add the id here
.id(imageName)
Here is the correct approach for this kind of issue:
We should not forgot how transition works!!! Transition modifier simply transmit a view to nothing or nothing to a view (This should be written with golden ink)! in your code there is no transition happening instead update happing.
struct ContentView: View {
#State var imageName1: String? = nil
#State var imageName2: String? = nil
var imageNames: [String] = ["applelogo", "peacesign", "heart", "lightbulb"]
#State var currentImage = -1
var body: some View {
VStack {
Spacer()
ZStack {
if let unwrappedImageName: String = imageName1 {
Image(systemName: unwrappedImageName)
.resizable()
.transition(AnyTransition.opacity)
.animation(nil, value: unwrappedImageName)
.scaledToFit()
}
if let unwrappedImageName: String = imageName2 {
Image(systemName: unwrappedImageName)
.resizable()
.transition(AnyTransition.opacity)
.animation(nil, value: unwrappedImageName)
.scaledToFit()
}
}
.padding()
.animation(.linear, value: [imageName1, imageName2])
Spacer()
Button("Press Me") {
currentImage = (currentImage == imageNames.count - 1 ? 0 : currentImage + 1)
if imageName1 == nil {
imageName2 = nil; imageName1 = imageNames[currentImage]
}
else {
imageName1 = nil; imageName2 = imageNames[currentImage]
}
}
}
}
}

How to trigger SwiftUI animation via change of non-State variable

It's easy to have an animation begin when a view appears, by using .onAppear(). But I'd like to perform a repeating animation whenever one of the view's non-State variables changes. An example:
Here is a view that I would like to "throb" whenever its throbbing parameter, set externally, is true:
struct MyCircle: View {
var throbbing: Bool
#State var scale = 1.0
var body: some View {
Circle()
.frame(width: 100 * scale, height: 100 * scale)
.foregroundColor(.blue)
.animation(.easeInOut.repeatForever(), value: scale)
.onAppear { scale = 1.2 }
}
}
Currently the code begins throbbing immediately, regardless of the throbbing variable.
But imagine this scenario:
struct ContentView: View {
#State var throb: Bool = false
var body: some View {
VStack {
Button("Throb: \(throb ? "ON" : "OFF")") { throb.toggle() }
MyCircle(throbbing: throb)
}
}
}
It looks like this:
Any ideas how I can modify MyCircle so that the throbbing starts when the button is tapped and ends when it is tapped again?
You can use onChange to watch throbbing and then assign an animation. If true, add a repeating animation, and if false, just animate back to the original scale size:
struct MyCircle: View {
var throbbing: Bool
#State private var scale : CGFloat = 0
var body: some View {
Circle()
.frame(width: 100, height: 100)
.scaleEffect(1 + scale)
.foregroundColor(.blue)
.onChange(of: throbbing) { newValue in
if newValue {
withAnimation(.easeInOut.repeatForever()) {
scale = 0.2
}
} else {
withAnimation {
scale = 0
}
}
}
}
}
There're two interesting things that i've just found when trying to achieve yours target.
Animation will be added when the value changed
Animation that added to the view cannot be removed, and we need to drop the animated view from the view hiearachy by remove its id, new view will be created with zero animations.
import SwiftUI
import PlaygroundSupport
struct ContentView: View {
#State var throbbling = false
#State var circleId = UUID()
var body: some View {
VStack {
Toggle("Throbbling", isOn: $throbbling)
circle.id(circleId)
.scaleEffect(throbbling ? 1.2 : 1.0)
.animation(.easeInOut.repeatForever(), value: throbbling)
.onChange(of: throbbling) { newValue in
if newValue == false {
circleId = UUID()
}
}
}.padding()
}
#ViewBuilder
var circle: some View {
Circle().fill(.green).frame(width: 100, height: 100)
}
}
PlaygroundPage.current.setLiveView(ContentView())

SwiftUI tvOS button animation - how to stop y axis movement

this simple code of x offset animation causes a text to move also on y axis when the text is part of a button (on tvOS 14.7)
struct Animate: View
{
#State var scrollText: Bool = false
var body: some View {
Button(action: {}, label: {
Text("This is My Text !")
.offset(x: scrollText ? 0 : 200, y: 0)
.animation(Animation.linear(duration: 1).repeatForever(autoreverses: true))
.onAppear {
self.scrollText.toggle()
}
})
}
}
see the animation behavior here:
marquee gone wrong
How can i stop the y axis movement ?
You always need to set a value for your animations. Otherwise, SwiftUI will animate all changes, include unwanted positioning.
struct Animate: View {
#State var scrollText: Bool = false
var body: some View {
Button(action: {}) {
Text("This is My Text !")
.offset(x: scrollText ? 0 : 200, y: 0)
.animation(Animation.linear(duration: 1).repeatForever(autoreverses: true), value: scrollText) /// only update animation when `scrollText` changes
.onAppear {
// DispatchQueue.main.async { /// you might also need this
self.scrollText.toggle()
// }
}
}
}
}
Result:
This video might also be helpful

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