The app I'm working on is SwiftUI (with TCA) and there is a requirement to send some Display Characteristics in our analytics.
Assumption: #Environment values are all updated in the same way, therefore the following code should get the same behaviour for colorScheme as it does for scenePhase.
#main
struct MyApp: App {
#UIApplicationDelegateAdaptor(MobileAppDelegate.self) private var appDelegate
#Environment(\.colorScheme) var colorScheme
#Environment(\.scenePhase) var scenePhase
var body: some Scene {
WindowGroup {
RootView(store: root)
.onChange(of: colorScheme) {
if colorScheme != $0 { appDelegate.viewStore.send(.didChangeColorScheme($0)) }
}
.onChange(of: scenePhase) {
if scenePhase != $0 { appDelegate.viewStore.send(.didChangeScenePhase($0)) }
}
.onAppear {
appDelegate.viewStore.send(.didChangeColorScheme(colorScheme))
appDelegate.viewStore.send(.didChangeScenePhase(scenePhase))
}
}
}
}
I receive every change to the scenePhase but none for the colorScheme. The onAppear does give me the initial value but if I log the colorScheme in the onChange handler of schenePhase, it never changes from the initial value. This seems to have broken my assumption. Is anyone aware of why and/or how I can get these (and others) to behave the same?
The assumption is still broken. EnvironmentValues are available at different scopes. The documentation for colorScheme and colorSchemeContrast suggests that they are only available from within a view...
Read this environment value from within a view
horizontal and vertical size classes also give a hint, but it's less clear
The value tells you about the amount of space available to the view that reads it.
There is no hint for the other Display Characteristics but they seem to be at the view level. I have not investigate other EnvironmentValues.
Related
Why is my SwiftUI Swipe Action behaving like this?
I don't now how to add a GIF in stack overflow so here is a imagur link https://imgur.com/a/9MqjIgX.
If you don't want to click on external links here is a image from the GIF:
My View:
struct MyView: View {
#State var shops = [Shop.empty(), Shop.empty(), Shop.empty(), Shop.empty(), Shop.empty()]
var body: some View {
NavigationView {
List($shops) { $shop in
Text(shop.name)
.swipeActions {
Button {
shop.toggleFavourite()
} label: {
Image(systemName: "star")
}
}
}
}
}
}
the shop struct:
struct Shop: Hashable, Identifiable {
var id: UUID
var favourite: Bool
init(id: UUID){
self.id = id
self.favourite = UserDefaults.standard.bool(forKey: id.uuidString)
}
mutating func toggleFavourite() {
favourite.toggle()
UserDefaults.standard.set(favourite, forKey: id.uuidString)
}
static func empty() -> Shop{
Shop(id: UUID())
}
}
But I can't sadly I can't give you a working example, because I tried to run this code in a fresh app and it worked, without the Bug. On the same device. And I don't understand why, because I also put this view in the root of my old project, just for testing, and the bug stayed there.
I was able to figure out, that if I commented out this line:
UserDefaults.standard.set(favourite, forKey: id.uuidString)
my code would work. But unfortunately I can't just leave out this line of code.
I tried several things, including wrapping this line into DispatchQueue.main.async {} and DispatchQueue.main.sync {}, same with the DispatchQueue.global(). I also added delays. Short delays wouldn't work at all (under .5 seconds) and longer delays would just delay the view bug.
Of course I also tried wrapping this line into a separate function, and so on.
There are two mayor points, why I'am so confused:
Why is the line, that sets this to the Userdefaults even influencing the view? I mean I checked with a print statement, that the initializer, which is the only section in my code that checks this Userdefaultvalue, only gets called when the view gets initialized.
Why does the code work in a different project?
I know since I can't provide a working example of my bug it's hard for you to figure out whats wrong. If you have any ideas, I would be very happy!
My swiftui application structure looks like this
Navigation View (enclosing the landing view that is a list view )
On selection of a List item Navigation link directs to a Tab View with three tabs (default first tab)
When I use a sole standalone navigation link inside tab view screens to direct to another screen programatically, it navigates succesfully to the mentioned destination, but my binding doesn't work to come back to the previous screen.
Parent View
#State var showCameraPreviewView : Bool = false
ZStack{
Button("Show camera") {
showCameraPreviewView = true
}
NavigationLink(destination: CameraView(showCameraPreviewView: $showCameraPreviewView),isActive: $showCameraPreviewView){
EmptyView()
}
}
Child View
#Binding var showCameraPreviewView
Button("Assume capture success"){
self.showCameraPreviewView = false
}
Toggling showCameraPreviewView binding to false in the destination doesn't get me back to the current screen.
Looks straight forward, but doesn't work ! anything that I'm doing wrong ?
I can reproduce your issue, quite strange ... seems like the change of showCameraPreviewView is not accepted because the view is still visible. But I found a workaround with dismiss:
EDIT for iOS 14:
struct ChildView: View {
#Environment(\.presentationMode) var presentationMode
#Binding var show: Bool
var body: some View {
Button("Assume capture success"){
show = false
presentationMode.wrappedValue.dismiss()
}
}
}
Is there anyway to keep the tab bar showing while presenting a modal / sheet view?
Here is a minimal failing example.
import SwiftUI
struct SheetView: View {
#Environment(\.dismiss) var dismiss
var body: some View {
Button("Press to dismiss") {
dismiss()
}
.padding()
}
}
struct Tab1: View {
#State private var showingSheet = false
var body: some View {
Button("Show Sheet") {
showingSheet.toggle()
}
.sheet(isPresented: $showingSheet) {
SheetView()
}
}
}
struct MainView: View {
var body: some View {
TabView {
Tab1()
.tabItem {
Label("Tab 1", systemImage: "heart")
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
MainView()
}
}
Thanks for answering my question in the comments.
Unfortunately the standard means of presenting views in SwiftUI is that they are truly modal – they capture the whole interaction context for the current scene, and you can’t interact with anything else until the modal is dismissed.
This is also the case for iPadOS. Even though a modal presented with .sheet on an iPad allows much more of the underlying view to be visible, you can’t interact with it until the sheet disappears. You can interact with different parts of the app by running two scenes side-by-side in split screen mode, but each half is a separate scene and any presented sheets are modal for that scene.
If you want one tab to optionally present a view over its usual content but still allow access to the tab view and its other tabs, that’s not a modal context and SwiftUI’s built-in sheet won’t work. You will have to implement something yourself - but I think that’s doable.
Rather than using .sheet, you could optionally add an overlay to your Tab1 view, using the same boolean state variable showingSheet. In this approach, the default dismiss environment variable won’t be available, so passing in the state variable as a binding value would be an alternative:
var body: some View
<main display>
.overlay(showingSheet ? Sheet1(presented: $showingSheet) : EmptyView())
You might also find that a ZStack works better than .overlay depending on what the contents of the tab view actually are.
You’ll definitely have a lot more structural work to do to make this work, but I hope you can see that it’s possible.
I'm dealing with what I am nearly certain to be a SwiftUI/Catalyst bug and am looking for a solution to get around it.
In the following code, about 30% of the time (5/15 in my tests), once the controls are revealed, the Toggle elements do not respond to clicks (and thus do not turn on/off).
I'm testing on Xcode 12.3 on Big Sur 11.1, running this code in Catalyst. It does work as expected 100% of the time as far as I can tell on iOS 14.3.
struct ContentView: View {
var body: some View {
ScrollView {
Row()
Row()
}
.padding()
}
}
struct Row : View {
#State private var showControls = false
#State private var toggleOn = false
var body: some View {
VStack {
HStack {
Text("Top section")
Button("\(showControls ? "Hide" : "Show") controls") {
showControls.toggle()
}
}
.frame(height: 100)
if showControls {
HStack {
Toggle("Toggle", isOn: $toggleOn)
Toggle("Toggle", isOn: $toggleOn)
}
}
}
}
}
The problem seems to come from having the Rows embedded in the ScrollView. The problem disappears completely if the controls start in their visible state (ie showControls = true), and only happens when they get revealed (ie showControls.toggle()) after the app starts.
I've also noticed that while Toggle and Slider fail about 30% of the time, a plain Button seems to be responsive 100% of the time.
The view debugger doesn't show anything 'in front' of the views that would be intercepting clicks.
I've tried changing to a List, which solves the problem, but yields other unfortunate side effects in behavior that I'd like to avoid in my real non-trivial app.
Can anyone else think of a reliable solution to avoiding this?
I created an ObservableObject that gathers data and a view that depends on this object. More specifically some parts of the UI depend on one property of it and other parts depend on other properties.
The way ObservableObject works is that if any of its Published property gets updated (event if it does not change) it sends an objectWillChange notification that triggers updates for subscribed views.
However, I did expect that only the parts of the views that depends on an ObservableObject property that actually changed would be updated, not the entire view because body computations are expensive.
Unfortunately this it not the behavior I observed during my experiments. For instance in the following code the List view depends only on the color dynamic property of the ObservedObject "preferences" and the TextField updates only the text property of the observed object. I observed with the debugPrint's that when I type text the List and its rows gets updated each time even if it does not depend on text.
struct ContentView: View {
#State private var list = ["foo", "bar", "baz"]
#StateObject private var preferences = Preferences()
var body: some View {
VStack {
List(list, id: \.self) { element in
Text(element)
.foregroundColor(preferences.color)
.debugPrint("Row view updated")
}
Spacer()
HStack {
TextField("Text", text: $preferences.text)
.debugPrint("Text field view updated")
Button("Toogle Color", action: toggleColor)
.debugPrint("Button view updated")
}
}
.padding()
.debugPrint("Content view updated")
}
func toggleColor() {
preferences.color = [.blue, .green, .orange, .red].randomElement()!
}
}
final class Preferences: ObservableObject {
#Published var color: Color = .blue
#Published var text: String = ""
}
extension View {
func debugPrint(_ elements: Any...) -> Self {
#if DEBUG
print(elements)
return self
#else
return self
#endif
}
}
Is this the correct and intended behavior? How the optimal behavior I described above could be obtained, i.e. not calling body when the ObservedObject changes but only the components that depends on specific properties?
I observed in bigger SwiftUI projects that this behavior can greatly slow down the application and is not easily debuggable because unique state is often enforced through heavy ObservedObjects (or StateObject) injected at the root view and used in many places. I Observed this behavior even with small lists of components with heavy UI layout.
Note 1: I was bugged by the StateObject definition which suggests that only the views that depend on those properties are updated (and not when the StateObject changes).
SwiftUI creates a new instance of the object only once for each
instance of the structure that declares the object. When published
properties of the observable object change, SwiftUI updates the parts
of any view that depend on those properties [...]
Note 2: The issue totally disappear if I define the List in its own component, the rendering is fast:
struct ListView: View {
let list: [String] // Also works with a #Binding
let color: Color // Also works if it would be `preferences`
var body: some View {
List {
ForEach(list, id: \.self) { element in
Row(text: element, color: color)
}
}
}
}
Why in this case the view updates are fast?