Use Case
If you have a ContentView that displays a pausable view based on a
@State private var presentSheet = false
property that is also used to present a
.sheet(isPresented: $presentSheet)
if:
the property is sent to the PausableView(isPaused: presentSheet) as a normal property, the body of the ContentView and the body of the sheet is being redrawn when the sheet is dismissed
the property is sent to the PausableView(isPaused: $presentSheet) as a @Binding, the body of the ContentView and the body of the sheet is NOT redrawn when the sheet is dismissed
Is this normal behavior?
The ContentView body makes sense to change, but is the sheet's body also supposed to be redrawn when the sheet is not presenting anymore after dismiss?
Sample Project
A sample project created in Xcode 13 is available here: https://github.com/clns/SwiftUI-sheet-redraw-on-dismiss. I noticed the same behavior on iOS 14 and iOS 15.
There are also 2 animated gifs showing the 2 different behaviors in the GitHub project.
The relevant code is in ContentView.swift:
import SwiftUI
struct DismissingView: View {
@Binding var isPresented: Bool
var body: some View {
if #available(iOS 15.0, *) {
print(Self._printChanges())
} else {
print("DismissingView: body draw")
}
return VStack {
Button("Dismiss") { isPresented.toggle() }
Text("Dismissing Sheet").padding()
}.background(Color.white)
}
}
struct PausableView: View {
var isPaused: Bool
// @Binding var isPaused: Bool
private let timer = Timer.publish(every: 1, on: .main, in: .common).autoconnect()
@State private var counter = 0
var body: some View {
Text("Elapsed seconds: \(counter)")
.onReceive(timer) { _ in
counter += isPaused ? 0 : 1
}
}
}
struct ContentView: View {
@State private var presentSheet = false
var body: some View {
if #available(iOS 15.0, *) {
print(Self._printChanges())
} else {
print("ContentView: body draw")
}
return VStack{
Button("Show Sheet") { presentSheet.toggle() }
Text("The ContentView's body along with the .sheet() is being redrawn immediately after dismiss, if the @State property `presentSheet` is used anywhere else in the view - e.g. passed to `PausableView(isPaused:presentSheet)`.\n\nBut if the property is passed as a @Binding to `PausableView(isPaused:$presentSheet)`, the ContentView's body is not redrawn.").padding()
PausableView(isPaused: presentSheet)
// PausableView(isPaused: $presentSheet)
}
.sheet(isPresented: $presentSheet) {
DismissingView(isPresented: $presentSheet)
.background(BackgroundClearView()) // to see what's happening under the sheet
}
}
}
