On occasion, whatever default animation exists in the still limited ScrollView in Swift UI, leads to a "compounding" animation effect.
ScrollView {
Text("Hello")
.animation(
Animation.interpolatingSpring(stiffness: 200, damping: 3)
)
}
This can, sometimes, lead to a much stronger spring effect (with respect to the offset) on initial load as the ScrollView gets rendered.
Is there a way to isolate the spring effect to the offset relative to itself rather than its absolute offset.
As interesting note is that if I turn the ScrollView into VStack this doesn't happen. It seemScrollView has some animation on initial render.
Alright here's a hack for anyone desperate:
struct Hack: View {
#State var show = false
public var body: some View {
ScrollView {
Text("Hello")
.animation(
Animation.interpolatingSpring(stiffness: 200, damping: 3)
)
.opacity(show ? 1 : 0) // this is the hack
.onAppear { self.show.toggle() }
}
}
}
This will disable the egregious (at least in my case) animation on the initial load. This really isn't a good answer nor an insight into whats happening with ScrollView.
Related
import SwiftUI
struct ContentView: View {
let letters = Array("Testing stuff")
#State private var enabled = false
#State private var dragAmount = CGSize.zero
var body: some View {
HStack(spacing: 0)
{
ForEach(0..<letters.count) { num in
Text(String(letters[num]))
.padding(5)
.font(.title)
.background(enabled ? .blue : .red)
.offset(dragAmount)
.clipShape(Circle())
.animation(.default.delay(Double(num) / 20), value: dragAmount)
}
}
.gesture(
DragGesture()
.onChanged { dragAmount = $0.translation}
.onEnded { _ in
dragAmount = .zero
enabled.toggle()
}
)
}
}
So I have this piece of code, I'm mostly just testing out animation stuff, originally the clipShape modifier was before the offset modifier and everything worked and went as expected, but when I move the clipShape modifier to be after the offset everything still animates but it seems like it's stuck in the Shape and I can't see anything outside the Circle.
Could someone maybe explain exactly why this is?
I understand the order of the modifiers is obviously very important in SwiftUI but to me it seems like whenever dragAmount changes then each view gets redrawn and offset and that offset modifier just notices changes in dragAmount and when it notices one it just offsets but why is it a problem if I put clipShape after that? Shouldn't it still totally be fine? I obviously don't understand why the order of the modifiers is important in this case so it would be nice if someone could clarify.
It doesn't work because the text is offsetted, and then clipShape clips the original location for the text.
Paul Hudson sums it up well:
Using offset() will cause a view to be moved relative to its natural position, but won’t affect the position of other views or any other modifiers placed after the offset.
- https://www.hackingwithswift.com/quick-start/swiftui/how-to-adjust-the-position-of-a-view-using-its-offset
Here, the only part you can see if the part of the yellow rectangle that is inside of the circle (outlined in red).
If you want the content to be clipped, then offsetted, use the clipShape modifier before the offset modifier.
Then it should look something like this (the part you can see is outlined in red):
Here I have this question when I try to give a View an initial position, then user can use drag gesture to change the location of the View to anywhere. Although I already solved the issue by only using .position(x:y:) on a View, at the beginning I was thinking using .position(x:y:) to give initial position and .offset(offset:) to make the View move with gesture, simultaneously. Now, I really just want to know in more detail, what exactly happens when I use both of them the same time (the code below), so I can explain what happens in the View below.
What I cannot explain in the View below is that: when I simply drag gesture on the VStack box, it works as expected and the VStack moves with finger gesture, however, once the gesture ends and try to start a new drag gesture on the VStack, the VStack box goes back to the original position suddenly (like jumping to the original position when the code is loaded), then start moving with the gesture. Note that the gesture is moving as regular gesture, but the VStack already jumped to a different position so it starts moving from a different position. And this causes that the finger tip is no long on top of the VStack box, but off for some distance, although the VStack moves with the same trajectory as drag gesture does.
My question is: why the .position(x:y:) modifier seems only take effect at the very beginning of each new drag gesture detected, but during the drag gesture action on it seems .offset(offset:) dominates the main movement and the VStack stops at where it was dragged to. But once new drag gesture is on, the VStack jumps suddenly to the original position. I just could not wrap my head around how this behavior happens through timeline. Can somebody provide some insights?
Note that I already solved the issue to achieve what I need, right now it's just to understand what is exactly going on when .position(x:y:) and .offset(offset:) are used the same time, so please avoid some advice like. not use them simultaneously, thank you. The code bellow suppose to be runnable after copy and paste, if not pardon me for making mistake as I delete few lines to make it cleaner to reproduce the issue.
import SwiftUI
struct ContentView: View {
var body: some View {
ButtonsViewOffset()
}
}
struct ButtonsViewOffset: View {
let location: CGPoint = CGPoint(x: 50, y: 50)
#State private var offset = CGSize.zero
#State private var color = Color.purple
var dragGesture: some Gesture {
DragGesture()
.onChanged{ value in
self.offset = value.translation
print("offset onChange: \(offset)")
}
.onEnded{ _ in
if self.color == Color.purple{
self.color = Color.blue
}
else{
self.color = Color.purple
}
}
}
var body: some View {
VStack {
Text("Watch 3-1")
Text("x: \(self.location.x), y: \(self.location.y)")
}
.background(Color.gray)
.foregroundColor(self.color)
.offset(self.offset)
.position(x: self.location.x, y: self.location.y)
.gesture(dragGesture)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
Group {
ContentView()
}
}
}
Your issue has nothing to do with the use of position and offset. They actually both work simultaneously. Position sets the absolute position of the view, where as offset moves it relative to the absolute position. Therefore, you will notice that your view starts at position (50, 50) on the screen, and then you can drag it all around. Once you let go, it stops wherever it was. So far, so good. You then want to move it around again, and it pops back to the original position. The reason it does that is the way you set up location as a let constant. It needs to be state.
The problem stems from the fact that you are adding, without realizing it, the values of offset to position. When you finish your drag, offset retains the last values. However, when you start your next drag, those values start at (0,0) again, therefore the offset is reset to (0,0) and the view moves back to the original position. The key is that you need to use just the position or update the the offset in .onEnded. Don't use both. Here you have a set position, and are not saving the offset. How you handle it depends upon the purpose for which you are moving the view.
First, just use .position():
struct OffsetAndPositionView: View {
#State private var position = CGPoint(x: 50, y: 50)
#State private var color = Color.purple
var dragGesture: some Gesture {
DragGesture()
.onChanged{ value in
position = value.location
print("position onChange: \(position)")
}
.onEnded{ value in
if color == Color.purple{
color = Color.blue
}
else{
color = Color.purple
}
}
}
var body: some View {
Rectangle()
.fill(color)
.frame(width: 30, height: 30)
.position(position)
.gesture(dragGesture)
}
}
Second, just use .offset():
struct ButtonsViewOffset: View {
#State private var savedOffset = CGSize.zero
#State private var dragValue = CGSize.zero
#State private var color = Color.purple
var offset: CGSize {
savedOffset + dragValue
}
var dragGesture: some Gesture {
DragGesture()
.onChanged{ value in
dragValue = value.translation
print("dragValue onChange: \(dragValue)")
}
.onEnded{ value in
savedOffset = savedOffset + value.translation
dragValue = CGSize.zero
if color == Color.purple{
color = Color.blue
}
else{
color = Color.purple
}
}
}
var body: some View {
Rectangle()
.fill(color)
.frame(width: 30, height: 30)
.offset(offset)
.gesture(dragGesture)
}
}
// Convenience operator overload
func + (lhs: CGSize, rhs: CGSize) -> CGSize {
return CGSize(width: lhs.width + rhs.width, height: lhs.height + rhs.height)
}
I was using CAMediaTimingFunction (for a window) and Animation.timingCurve (for the content) with the same Bézier curve and time to deal with the resizing. However, there can be a very small time difference and therefore it caused the window to flicker irregularly. Just like this (GitHub repository: http://github.com/toto-minai/DVD-Player-Components ; original design by 7ahang):
Red background indicates the whole window, while green background indicates the content. As you can see, the red background is visible at certain points during the animation, which means that the content is sometimes smaller than the window, so it generates extra small spaces and causes unwanted shaking.
In AppDelegate.swift, I used a custom NSWindow class for the main window and overrode setContentSize():
class AnimatableWindow: NSWindow {
var savedSize: CGSize = .zero
override func setContentSize(_ size: NSSize) {
if size == savedSize { return }
savedSize = size
NSAnimationContext.runAnimationGroup { context in
context.timingFunction = CAMediaTimingFunction(controlPoints: 0, 0, 0.58, 1.00) // Custom Bézier curve
context.duration = animationTime // Custom animation time
animator().setFrame(NSRect(origin: frame.origin, size: size), display: true, animate: true)
}
}
}
In ContentView.swift, the main structure (simplified):
struct ContentView: View {
#State private var showsDrawer: Bool = false
var body: some View {
HStack {
SecondaryAdjusters() // Left panel
HStack {
Drawer() // Size-changing panel
.frame(width: showsDrawer ? 175 : 0, alignment: .trailing)
DrawerBar() // Right bar
.onTapGesture {
withAnimation(Animation.timingCurve(0, 0, 0.58, 1.00, duration: animationTime)) { // The same Bézier curve and animation time
showsDrawer.toggle()
}
}
}
}
}
}
The animated object is the size-changing Drawer() in the middle. I suppose that it is because the different frame rate of two methods. I'm wondering how to synchronise the two functions, and whether there's another way to implement drawer-like View in SwiftUI. You could clone the repository here. Thanks for your patient.
In my project, I have a SCNView encapsulated in UIViewRepresentable, that should resize in height according to the DragGesture of another view.
The issue is that when dragging, or after drag gesture ended, the memory usage is abnormally high. Checking for memory leaks in Instruments yielded no leaks. It also only occurs in a physical device, not in Simulator.
When using the Simulator,
The memory use is stable at around 19MB, regardless of resizing or not.
When using a physical device,
The memory use spiked badly upon each resize, and doesn't fall after end. (Worst I've seen was around 1.9GB of memory usage, before crash.)
Any experts here know the reason why it happens, and how to fix it? Thanks in advance.
UPDATE: I noticed that after DragGesture ended, if I were to move the camera of the SCNView, the memory will drop back to normal values.
Heres the code of the main ContentView.
Basically its a split view layout where if I were to adjust the RoundedRectangle (which acts as a handle), the top and bottom views will resize. It is when resizing that will cause the memory spike issue, which, at worst, will cause a crash, and Message from debugger: Terminated due to memory issue.
VStack {
SceneView()
.frame(height: (UIScreen.main.bounds.height / 2) + self.gestureTranslation.height)
RoundedRectangle(cornerRadius: 5)
.frame(width: 40, height: 6)
.foregroundColor(Color.gray)
.padding(2)
.gesture(DragGesture(coordinateSpace: .global)
.onChanged({ value in
self.gestureTranslation = CGSize(width: value.translation.width + self.prevTranslation.width, height: value.translation.height + self.prevTranslation.height)
})
.onEnded({ value in
self.gestureTranslation = CGSize(width: value.translation.width + self.prevTranslation.width, height: value.translation.height + self.prevTranslation.height)
self.prevTranslation = self.gestureTranslation
})
)
Rectangle()
.fill(Color.green)
.frame(height: (UIScreen.main.bounds.height / 2) - self.gestureTranslation.height)
}
}
Heres the code for the UIViewRepresentable wrapper for the SCNView.
struct SceneView: UIViewRepresentable {
typealias UIViewType = SCNView
func makeUIView(context: Context) -> SCNView {
let scene = SCNScene(named: "SceneAssets.scnassets/Cube.scn")
let view = SCNView()
view.scene = scene
view.allowsCameraControl = true
view.defaultCameraController.interactionMode = .orbitTurntable
view.defaultCameraController.inertiaEnabled = true
return view
}
func updateUIView(_ uiView: SCNView, context: Context) {
}
}
Here's the full test project that I've made to describe the issue: https://github.com/vincentneo/swiftui-scnview-memory-issue
I am trying to replicate a long press button effect like the Apple default one, but with a custom style.
I have a custom view where I call onLongPressGesture. The issue is that the pressing variable is getting set to false even though my finger is still pressing.
I just move my finger outside the the views onLongPressGesture frame.
I want the pressing variable to not get set to false when I move my finger outside the frame area.
How can i achieve that?
Here's my code:
.onLongPressGesture(minimumDuration: 1000000000, maximumDistance: 100, pressing: {
pressing in
if !pressing {
self.action?()
self.showNextScreen = true
} else {
withAnimation(.spring()) {
self.showGrayBackgound = true
}
}
}) { }
Use the maximumDistance parameter to set how far outside the view the gesture applies:
struct LongPressView: View {
#State var isPressing = false
let action: ()->()
var body: some View {
Rectangle()
.fill(isPressing ? Color.orange : .gray)
.frame(width: 50, height: 30)
.onLongPressGesture(minimumDuration: 1000000, maximumDistance: 1000, pressing: { pressing in
self.isPressing = pressing
if !pressing { self.action() }
}, perform: {})
}
}
A sufficiently large maximumDistance will be outside the boundary of the screen and the long press will remain active until it's released. However, the macOS behavior where you click and hold while dragging outside the frame and back so that the button's state is turned off and back on isn't possible with a LongPressGesture. Once outside the maximumDistance, the gesture is complete.