Is it possible to have gestures such as Magnification Gestures on a View. I would like to do this so I can scale multiple items at once.
I wrote the following, but the gesture never gets called on the View. Although it works on many other objects like text, images, colorsquares . . .
struct TestView: View {
#State var newScale: CGFloat = 1.0
var body: some View {
TestView1()
.scaleEffect(newScale)
.gesture (
MagnificationGesture()
.onChanged { gesture in
self.newScale = gesture
}
)
}
}
Thanks for any help!!
Try this code from the Apple Documentation.
struct MagnificationGestureView: View {
#GestureState var magnifyBy = 1.0
var magnification: some Gesture {
MagnificationGesture()
.updating($magnifyBy) { currentState, gestureState, transaction in
gestureState = currentState
}
}
var body: some View {
TestViewOne()
.frame(width: 100, height: 100)
.scaleEffect(magnifyBy)
.gesture(magnification)
}
}
I think the .updating modifier is key here. Docs for that: https://developer.apple.com/documentation/swiftui/gesture/updating(_:body:)/. Once again, this code is a slight modification of the code on the Apple Docs. Link here: https://developer.apple.com/documentation/swiftui/magnificationgesture.
Related
I am trying to achieve drag and magnification gestures take in place simultaneously. With the code below, I was able to achieve transitioning dragging to magnifying, however, when I release one finger after magnification, the drag gesture is killed even though one finger is still on the rectangle. In the Photos app in iOS, you can magnify and release one finger then you can still drag an image. I have looked at Simultaneous MagnificationGesture and DragGesture with SwiftUI. Has this been fixed since then? If not, is there any way to achieve this by using UIViewRepresentable?
import SwiftUI
struct DragAndMagnificationGestures: View {
#State private var currentAmount = 0.0
#State private var finalAmount = 1.0
#State private var dragGestureOffset: CGSize = .zero
var body: some View {
VStack {
let combined = dragGesture.simultaneously(with: magnificationGesture)
Rectangle()
.frame(width: 200, height: 200)
.scaleEffect(finalAmount + currentAmount)
.offset(dragGestureOffset)
.gesture(combined)
}
}
}
struct MultiGesture_Previews: PreviewProvider {
static var previews: some View {
DragAndMagnificationGestures()
}
}
extension DragAndMagnificationGestures {
private var dragGesture: some Gesture {
DragGesture()
.onChanged { value in
if finalAmount != 0 {
withAnimation(.spring()) {
dragGestureOffset = value.translation
}
}
}
.onEnded({ value in
withAnimation(.spring()) {
dragGestureOffset = .zero
}
})
}
private var magnificationGesture: some Gesture {
MagnificationGesture()
.onChanged { amount in
currentAmount = amount - 1
}
.onEnded({ amount in
finalAmount += currentAmount
currentAmount = 0
})
}
}
I found this article regarding the same problem as I have:
Spinner animation starts bouncing once the view is updated
However, the best solution given does not appear to work in my case. It could well be I have missed something in the solution, but I cannot see anything!
struct OscillatingTextView: View
{
#State var doAnimation = false
var text: String
var animation: Animation {
Animation.easeInOut(duration: 1.0)
.repeatForever(autoreverses: true)
}
var body: some View {
HStack{
ForEach(Array(text), id: \.self)
{ letter in
Text(String(letter))
.rotationEffect(Angle.degrees(doAnimation ? 30:-30))
.animation(doAnimation ? animation : .default, value: doAnimation) //as advised in Asperi solution
}
.font(.largeTitle)
}
.onAppear()
{
doAnimation.toggle()
}
}
}
In SwiftUI, I've managed to make a Button animate right when the view is first drawn to the screen, using the animation(_:) modifier, that was deprecated in macOS 12.
I've tried to replace this with the new animation(_:value:) modifier, but this time nothing happens:
So this is not working:
struct ContentView: View {
#State var isOn = false
var body: some View {
Button("Press me") {
isOn.toggle()
}
.animation(.easeIn, value: isOn)
.frame(width: 300, height: 400)
}
}
But then this is working. Why?
struct ContentView: View {
var body: some View {
Button("Press me") {
}
.animation(.easeIn)
.frame(width: 300, height: 400)
}
}
The second example animates the button just as the view displays, while the first one does nothing
The difference between animation(_:) and animation(_:value:) is straightforward. The former is implicit, and the latter explicit. The implicit nature of animation(_:) meant that anytime ANYTHING changed, it would react. The other issue it had was trying to guess what you wanted to animate. As a result, this could be erratic and unexpected. There were some other issues, so Apple has simply deprecated it.
animation(_:value:) is an explicit animation. It will only trigger when the value you give it changes. This means you can't just stick it on a view and expect the view to animate when it appears. You need to change the value in an .onAppear() or use some value that naturally changes when a view appears to trigger the animation. You also need to have some modifier specifically react to the changed value.
struct ContentView: View {
#State var isOn = false
//The better route is to have a separate variable to control the animations
// This prevents unpleasant side-effects.
#State private var animate = false
var body: some View {
VStack {
Text("I don't change.")
.padding()
Button("Press me, I do change") {
isOn.toggle()
animate = false
// Because .opacity is animated, we need to switch it
// back so the button shows.
DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
animate = true
}
}
// In this case I chose to animate .opacity
.opacity(animate ? 1 : 0)
.animation(.easeIn, value: animate)
.frame(width: 300, height: 400)
// If you want the button to animate when the view appears, you need to change the value
.onAppear { animate = true }
}
}
}
Follow up question: animating based on a property of an object is working on the view itself, but when I'm passing that view its data through a ForEach in the parent view, an animation modifier on that object in the parent view is not working. It won't even compile. The objects happen to be NSManagedObjects but I'm wondering if that's not the issue, it's that the modifier works directly on the child view but not on the passed version in the parent view. Any insight would be greatly appreciated
// child view
struct TileView: View {
#ObservedObject var tile: Tile
var body: some View {
Rectangle()
.fill(tile.fillColor)
.cornerRadius(7)
.overlay(
Text(tile.word)
.bold()
.font(.title3)
.foregroundColor(tile.fillColor == .myWhite ? .darkBlue : .myWhite)
)
// .animation(.easeInOut(duration: 0.75), value: tile.arrayPos)
// this modifier worked here
}
}
struct GridView: View {
#ObservedObject var game: Game
let columns: [GridItem] = Array(repeating: .init(.flexible()), count: 4)
var body: some View {
GeometryReader { geo in
LazyVGrid(columns: columns) {
ForEach(game.tilesArray, id: \.self) { tile in
Button(action: {
tile.toggleSelectedStatus()
moveTiles() <- this changes their array position (arrayPos), and
the change in position should be animated
}) {
TileView(tile: tile)
.frame(height: geo.size.height * 0.23)
}
.disabled(tile.status == .solved || tile.status == .locked)
.animation(.easeInOut(duration: 0.75), value: arrayPos)
.zIndex(tile.status == .locked ? 1 : 0)
}
}
}
}
}
I am starting out in SwiftUI and have an issue.
I have a main view loads a modal view, on iPhone this goes full screen, iPad by default covers part of the screen.
The below code appears to do the 'default' loads a view that is centered but not full screen.
What id ideally like is to be able to make the model view smaller. It is a login screen where user enters login details.
Using storyboards, I could achieve this with 'preferredcontentsize' but SwiftUI comparisons don't appear to work.
struct Login_View: View {
#State private var showingSheet = false
var body: some View {
Button("Show Alert") {
showingSheet = !showingSheet
}
.sheet(isPresented:$showingSheet) {
Credentials_View()
}
}
}
(Below is the modal view, atm it just shows some colours whilst I get to grips with that is going on)
struct Credentials_View: View {
var body: some View {
GeometryReader { metrics in
VStack(spacing: 0) {
Color.red.frame(height: metrics.size.height * 0.43)
Color.green.frame(height: metrics.size.height * 0.37)
Color.yellow
}
}
}
}
IOS 16+
As of iOS 16, a half sheet can be created using .sheet where the displayed view(example Credentials_View) has the .presentationDetents set to .medium.
struct Login_View: View {
#State private var showingSheet = false
var body: some View {
Button("Show Alert") {
showingSheet = !showingSheet
}
.sheet(isPresented:$showingSheet) {
Credentials_View()
.presentationDetents([.medium])
}
}
}
Result:
And .presentationDragIndicator can be added to make the indicator visible:
.presentationDragIndicator(.visible)
Result:
Revised Example
Based on the thoughtful response from #pawello2222 I received in the comments below I have revised an example to demonstrate the issue I am wrestling with.
In order to demonstrate the issue I am having I am using 2 views a parent and a child. In my code code the parent view executes multiple steps but sometimes the animation subview is not visible in the first step. However when it does become visible the animation has already taken on the appearance of the end state. You can see this behavior in the following example.
Parent View
struct ContentView: View {
#State var firstTime = true
#State var breath = false
var body: some View {
VStack {
// This subview is not displayed until after the first time
if !firstTime {
SecondView(breath: $breath)
}
Spacer()
// A button click simulates the steps in my App by toggling the #Binding var
Button("Breath") {
withAnimation {
self.breath.toggle()
self.firstTime = false
}
}
// This vies shows what happens when the subview is being displayed with an intial state of false for the #Binding var
Spacer()
SecondView(breath: $breath)
}
}
}
Here is the subview containing the animation and using a #Binding var to control the animation appearance.
struct SecondView: View {
#Binding var breath: Bool
var body: some View {
Image(systemName: "flame")
.resizable()
.rotationEffect(.degrees(breath ? 360 : 0), anchor: .center)
.scaleEffect(breath ? 1 : 0.2)
.opacity(breath ? 1 : 0.75)
.animation(.easeInOut(duration: 2))
.foregroundColor(Color.red)
}
}
When you execute this the first time thru the top subview is not being displayed and when you click the button the lower subview executes the expected animation and then toggles the firstTime var so that the top subview becomes visible. Notice that the animation is fully expanded and if I was to then have another step (click) with the same value of true for the #Binding property the view would not change at all. This is the issue I am wrestling with. I would like to keep the subview from being at the end state if the first step is one that has toggled the Bool value even if the subview was not being displayed. In other words I would like to only initialize the subview when it is actually being displayed with a value of true so that the animation will always start out small.
This is why I was hoping to have the subview initialized the Binding var to false until it actually gets invoked for the first time (or to reset its state to the shrunk version of the animation) whichever is more feasible.
It looks like you may want to initialise _breath with the provided parameter:
struct ContentView: View {
#Binding var breath: Bool
init(breath: Binding<Bool>) {
_breath = breath
}
}
However, if you want to use a constant value (in your example false) you can do:
struct ContentView: View {
#Binding var breath: Bool
init(breath: Binding<Bool>) {
_breath = .constant(false)
}
}
But then, why do you need the breath: Binding<Bool> parameter?
EDIT
Here is an example how to control an animation of a child view using a #Binding variable:
struct ContentView: View {
#State var breath = false
var body: some View {
VStack {
Button("Breath") {
withAnimation {
self.breath.toggle()
}
}
SecondView(breath: $breath)
}
}
}
struct SecondView: View {
#Binding var breath: Bool
var body: some View {
Image(systemName: "flame")
.imageScale(.large)
.rotationEffect(.degrees(breath ? 360 : 0), anchor: .center)
.scaleEffect(breath ? 1 : 0.2)
.opacity(breath ? 1 : 0.75)
.animation(.easeInOut(duration: 2))
}
}