Why doesn't the button's image background show up in toolbar using SwiftUI? - swift

Question

In Apple's calendar app, they provide a toolbar item that toggles its style based on some state. It essentially acts as a Toggle. I'm trying to re-create this same thing in SwiftUI and make it work well in both light and dark mode. I was able to make a view that works as intended, until I put it into the toolbar and it no longer shows the selected state. Here is my attempt:
struct ToggleButtonView: View {
#State private var isOn = false
var body: some View {
Button(action: {
isOn.toggle()
}, label: {
if isOn {
Image(systemName: "list.bullet.below.rectangle")
.accentColor(Color(.systemBackground))
.background(RoundedRectangle(cornerRadius: 5.0)
.fill(Color.accentColor)
.frame(width: 26, height: 26))
} else {
Image(systemName: "list.bullet.below.rectangle")
}
})
.accentColor(.red)
}
}
And here is how I am actually placing the button into the toolbar:
struct TestView: View {
var body: some View {
NavigationView {
ScrollView {
ForEach(0..<5) { number in
Text("Number \(number)")
}
}
.toolbar {
ToolbarItemGroup(placement: .navigationBarTrailing) {
ToggleButtonView()
Button(action: {}, label: {
Image(systemName: "plus")
})
}
}
.navigationTitle("Plz halp")
}
.accentColor(.red)
}
}
Here are screenshots from the calendar app. Notice the toolbar item to the left of the search icon.

Answer 1

you could try this:
.toolbar {
// placement as you see fit
ToolbarItem(placement: .navigationBarTrailing) {
ToggleButtonView()
}
ToolbarItem(placement: .navigationBarTrailing) {
Button(action: {}, label: {
Image(systemName: "plus")
})
}
}

Answer 2

This looks like an issue with how SwiftUI handles ToolbarItems before iOS 15. According to Asperi's answer to a similar question, "...all standards types (button, image, text, etc) are intercepted by ToolbarItem and converted into an appropriate internal representation."
Toggle buttons in SwiftUI iOS 15
Interestingly enough, iOS 15 now provides a standard solution to the use-case above using the .button toggle style, as shown in the following code:
struct ContentView: View {
#State private var isOn = false
var body: some View {
Toggle(isOn: $isOn) {
Image(systemName: "list.bullet.below.rectangle")
}
}
}