SwiftUI: Global Overlay That Can Be Triggered From Any View - swift

Question

I'm quite new to the SwiftUI framework and I haven't wrapped my head around all of it yet so please bear with me.
Is there a way to trigger an "overlay view" from inside "another view" when its binding changes? See illustration below:
I figure this "overlay view" would wrap all my views. I'm not sure how to do this yet - maybe using ZIndex. I also guess I'd need some sort of callback when the binding changes, but I'm also not sure how to do that either.
This is what I've got so far:
ContentView
struct ContentView : View {
#State private var liked: Bool = false
var body: some View {
VStack {
LikeButton(liked: $liked)
}
}
}
LikeButton
struct LikeButton : View {
#Binding var liked: Bool
var body: some View {
Button(action: { self.toggleLiked() }) {
Image(systemName: liked ? "heart" : "heart.fill")
}
}
private func toggleLiked() {
self.liked = !self.liked
// NEED SOME SORT OF TOAST CALLBACK HERE
}
}
I feel like I need some sort of callback inside my LikeButton, but I'm not sure how this all works in Swift.
Any help with this would be appreciated. Thanks in advance!

Answer 1

It's quite easy - and entertaining - to build a "toast" in SwiftUI!
Let's do it!
struct Toast<Presenting>: View where Presenting: View {
/// The binding that decides the appropriate drawing in the body.
#Binding var isShowing: Bool
/// The view that will be "presenting" this toast
let presenting: () -> Presenting
/// The text to show
let text: Text
var body: some View {
GeometryReader { geometry in
ZStack(alignment: .center) {
self.presenting()
.blur(radius: self.isShowing ? 1 : 0)
VStack {
self.text
}
.frame(width: geometry.size.width / 2,
height: geometry.size.height / 5)
.background(Color.secondary.colorInvert())
.foregroundColor(Color.primary)
.cornerRadius(20)
.transition(.slide)
.opacity(self.isShowing ? 1 : 0)
}
}
}
}
Explanation of the body:
GeometryReader gives us the preferred size of the superview , thus allowing the perfect sizing for our Toast.
ZStack stacks views on top of each other.
The logic is trivial: if the toast is not supposed to be seen (isShowing == false), then we render the presenting view. If the toast has to be presented (isShowing == true), then we render the presenting view with a little bit of blur - because we can - and we create our toast next.
The toast is just a VStack with a Text, with custom frame sizing, some design bells and whistles (colors and corner radius), and a default slide transition.
I added this method on View to make the Toast creation easier:
extension View {
func toast(isShowing: Binding<Bool>, text: Text) -> some View {
Toast(isShowing: isShowing,
presenting: { self },
text: text)
}
}
And a little demo on how to use it:
struct ContentView: View {
#State var showToast: Bool = false
var body: some View {
NavigationView {
List(0..<100) { item in
Text("\(item)")
}
.navigationBarTitle(Text("A List"), displayMode: .large)
.navigationBarItems(trailing: Button(action: {
withAnimation {
self.showToast.toggle()
}
}){
Text("Toggle toast")
})
}
.toast(isShowing: $showToast, text: Text("Hello toast!"))
}
}
I used a NavigationView to make sure the view fills the entire screen, so the Toast is sized and positioned correctly.
The withAnimation block ensures the Toast transition is applied.
How it looks:
It's easy to extend the Toast with the power of SwiftUI DSL.
The Text property can easily become a #ViewBuilder closure to accomodate the most extravagant of the layouts.
To add it to your content view:
struct ContentView : View {
#State private var liked: Bool = false
var body: some View {
VStack {
LikeButton(liked: $liked)
}
// make it bigger by using "frame" or wrapping it in "NavigationView"
.toast(isShowing: $liked, text: Text("Hello toast!"))
}
}
How to hide the toast afte 2 seconds (as requested):
Append this code after .transition(.slide) in the toast VStack.
.onAppear {
DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
withAnimation {
self.isShowing = false
}
}
}
Tested on Xcode 11.1

Answer 2

I modified Matteo Pacini's great answer, above, incorporating comments to have the Toast fade in and fade out after a delay. I also modified the View extension to be a bit more generic, and to accept a trailing closure similar to the way .sheet works.
ContentView.swift:
struct ContentView: View {
#State private var lightsOn: Bool = false
#State private var showToast: Bool = false
var body: some View {
VStack {
Button(action: {
if (!self.showToast) {
self.lightsOn.toggle()
withAnimation {
self.showToast = true
}
}
}){
Text("switch")
} //Button
.padding(.top)
Image(systemName: self.lightsOn ? "lightbulb" : "lightbulb.fill")
.resizable()
.aspectRatio(contentMode: .fit)
.padding(.all)
.toast(isPresented: self.$showToast) {
HStack {
Text("Lights: \(self.lightsOn ? "ON" : "OFF")")
Image(systemName: self.lightsOn ? "lightbulb" : "lightbulb.fill")
} //HStack
} //toast
} //VStack
} //body
} //ContentView
View+Toast.swift:
extension View {
func toast<Content>(isPresented: Binding<Bool>, content: #escaping () -> Content) -> some View where Content: View {
Toast(
isPresented: isPresented,
presenter: { self },
content: content
)
}
}
Toast.swift:
struct Toast<Presenting, Content>: View where Presenting: View, Content: View {
#Binding var isPresented: Bool
let presenter: () -> Presenting
let content: () -> Content
let delay: TimeInterval = 2
var body: some View {
if self.isPresented {
DispatchQueue.main.asyncAfter(deadline: .now() + self.delay) {
withAnimation {
self.isPresented = false
}
}
}
return GeometryReader { geometry in
ZStack(alignment: .bottom) {
self.presenter()
ZStack {
Capsule()
.fill(Color.gray)
self.content()
} //ZStack (inner)
.frame(width: geometry.size.width / 1.25, height: geometry.size.height / 10)
.opacity(self.isPresented ? 1 : 0)
} //ZStack (outer)
.padding(.bottom)
} //GeometryReader
} //body
} //Toast
With this you could toast Text, or an Image (or both, as shown below), or any other View.

Answer 3

here is the how to overlay on all of your views including NavigationView!
create a class model to store your views!
class ParentView:ObservableObject {
#Published var view:AnyView = AnyView(EmptyView())
}
create the model in your parrent view and call it in your view hierarchy
pass this class to your environment object of your parent view
struct Example: View {
#StateObject var parentView = ParentView()
var body: some View {
ZStack{
NavigationView{
ChildView()
.environmentObject(parentView)
.navigationTitle("dynamic parent view")
}
parentView.view
}
}
}
from now on you can call parentview in your child view by
#EnvironmentObject var parentView:ParentView
then for example in your tap gesture, you can change the parent view and show a pop up that covers everything including your navigationviews
#StateObject var parentView = ParentView()
here is the full solution copy and play with it in your preview!
import SwiftUI
class ParentView:ObservableObject {
#Published var view:AnyView = AnyView(EmptyView())
}
struct example: View {
#StateObject var parentView = ParentView()
var body: some View {
ZStack{
NavigationView{
ChildView()
.environmentObject(parentView)
.navigationTitle("dynamic parent view")
}
parentView.view
}
}
}
struct ChildView: View {
#EnvironmentObject var parentView:ParentView
var body: some View {
ZStack{
Text("hello")
.onTapGesture {
parentView.view = AnyView(Color.red.opacity(0.4).ignoresSafeArea())
}
}
}
}
struct example_Previews: PreviewProvider {
static var previews: some View {
example()
}
}
also you can improve this dramatically like this...!
struct ParentViewModifire:ViewModifier {
#EnvironmentObject var parentView:ParentView
#Binding var presented:Bool
let anyView:AnyView
func body(content: Content) -> some View {
content
.onChange(of: presented, perform: { value in
if value {
parentView.view = anyView
}
})
}
}
extension View {
func overlayAll<Overlay>(_ overlay: Overlay, presented: Binding<Bool>) -> some View where Overlay : View {
self
.modifier(ParentViewModifire(presented: presented, anyView: AnyView(overlay)))
}
}
now in your child view you can call this modifier on your view
struct ChildView: View {
#State var newItemPopUp:Bool = false
var body: some View {
ZStack{
Text("hello")
.overlayAll(newCardPopup, presented: $newItemPopUp)
}
}
}

Answer 4

App-wide View
If you want it to be app-wide, put in somewhere app-wide! For example, you can add it to the MyProjectApp.swift (or in sceneDelegate for UIKit/AppDelegate projects) file like this:
Note that the button and the State are just for more explanation and you may consider changing them in the way you like
#main
struct SwiftUIAppPlaygroundApp: App { // <- Note that where we are!
#State var showToast = false
var body: some Scene {
WindowGroup {
Button("App-Wide Button") { showToast.toggle() }
ZStack {
ContentView() // <- The app flow
if showToast {
MyCustomToastView().ignoresSafeArea(.all, edges: .all) // <- App-wide overlays
}
}
}
}
}
See? now you can add any sort of view on anywhere of the screen, without blocking animations. Just convert that #State to some sort of AppState like Observables or Environments and boom! 💥 you did it!
Note that it is a demo, you should use an environment variable or smt to be able for changing it from outside of this view's body

Answer 5

Apple does not currently provide any APIs that allow you to make global views similar to their own alert pop-ups.
In fact these views are actually still using UIKit under the hood.
If you want your own global pop-ups you can sort of hack your own (note this isn't tested, but something very similar should work for global presentation of toasts):
import SwiftUI
import Foundation
/// Global class that will manage toasts
class ToastPresenter: ObservableObject {
// This static property probably isn't even needed as you can inject via #EnvironmentObject
static let shared: ToastPresenter = ToastPresenter()
private init() {}
#Published private(set) var isPresented: Bool = false
private(set) var text: String?
private var timer: Timer?
/// Call this function to present toasts
func presentToast(text: String, duration: TimeInterval = 5) {
// reset the toast if one is currently being presented.
isPresented = false
self.text = nil
timer?.invalidate()
self.text = text
isPresented = true
timer = Timer(timeInterval: duration, repeats: false) { [weak self] _ in
self?.isPresented = false
}
}
}
/// The UI for a toast
struct Toast: View {
var text: String
var body: some View {
Text(text)
.padding()
.background(Capsule().fill(Color.gray))
.shadow(radius: 6)
.transition(AnyTransition.opacity.animation(.default))
}
}
extension View {
/// ViewModifier that will present a toast when its binding changes
#ViewBuilder func toast(presented: Binding<Bool>, text: String) -> some View {
ZStack {
self
if presented.wrappedValue {
Toast(text: text)
}
}
.ignoresSafeArea(.all, edges: .all)
}
}
/// The first view in your app's view hierarchy
struct RootView: View {
#StateObject var toastPresenter = ToastPresenter.shared
var body: some View {
MyAppMainView()
.toast(presented: $toastPresenter.isPresented, text: toastPresenter.text)
// Inject the toast presenter into the view hierarchy
.environmentObject(toastPresenter)
}
}
/// Some view later on in the app
struct SomeViewDeepInTheHierarchy: View {
#EnvironmentObject var toastPresenter: ToastPresenter
var body: some View {
Button {
toastPresenter.presentToast(text: "Hello World")
} label: {
Text("Show Toast")
}
}
}

Answer 6

Use .presentation() to show an alert when the button is tapped.
In LikeButton:
#Binding var liked: Bool
var body: some View {
Button(action: {self.liked = !self.liked}, label: {
Image(systemName: liked ? "heart.fill" : "heart")
}).presentation($liked) { () -> Alert in
Alert.init(title: Text("Thanks for liking!"))
}
}
You can also use .presentation() to present other Modal views, like a Popover or ActionSheet. See here and the "See Also" section on that page in Apple's SwiftUI documentation for info on the different .presentation() options.
Edit: Example of what you want with a custom view using Popover:
#State var liked = false
let popover = Popover(content: Text("Thanks for liking!").frame(width: 200, height: 100).background(Color.white), dismissHandler: {})
var body: some View {
Button(action: {self.liked = !self.liked}, label: {
Image(systemName: liked ? "heart.fill" : "heart")
}).presentation(liked ? popover : nil)
}

Answer 7

I am using this open source: https://github.com/huynguyencong/ToastSwiftUI . It is very simple to use.
struct ContentView: View {
#State private var isShowingToast = false
var body: some View {
VStack(spacing: 20) {
Button("Show toast") {
self.isShowingToast = true
}
Spacer()
}
.padding()
// Just add a modifier to show a toast, with binding variable to control
.toast(isPresenting: $isShowingToast, dismissType: .after(3)) {
ToastView(message: "Hello world!", icon: .info)
}
}
}