I would like to create a view in SwiftUI that add a subview dynamically and with animation.
struct ContentView : View {
@State private var isButtonVisible = false
var body: some View {
VStack {
Toggle(isOn: $isButtonVisible.animation()) {
Text("add view button")
}
if isButtonVisible {
AnyView(DetailView())
.transition(.move(edge: .trailing))
.animation(Animation.linear(duration: 2))
}else{
AnyView(Text("test"))
}
}
}
}
The above code works fine with the animation. however when i move the view selection part into a function, the animation is not working anymore (since i want to add different views dynamically, therefore, I put the logic in a function.)
struct ContentView : View {
@State private var isButtonVisible = false
var body: some View {
VStack {
Toggle(isOn: $isButtonVisible.animation()) {
Text("add view button")
}
subView().transition(.move(edge: .trailing))
.animation(Animation.linear(duration: 2))
}
func subView() -> some View {
if isButtonVisible {
return AnyView(DetailView())
}else{
return AnyView(Text("test"))
}
}
}
it looks totally the same to me, however, i don't understand why they have different result. Could somebody explain me why? and any better solutions? thanks alot!
Here's your code, modified so that it works:
struct ContentView : View {
@State private var isButtonVisible = false
var body: some View {
VStack {
Toggle(isOn: $isButtonVisible.animation()) {
Text("add view button")
}
subView()
.transition(.move(edge: .trailing))
.animation(Animation.linear(duration: 2))
}
}
func subView() -> some View {
Group {
if isButtonVisible {
DetailView()
} else {
Text("test")
}
}
}
}
Note two things:
Group
view. Then the type you return is Group
, which will animate properly.DetailView()
or Text("test")
.Update
The Group
method will only work with if
, elseif
, and else
statements. If you want to use a switch, you will have to wrap each branch in AnyView()
. However, this breaks transitions/animations. Using switch
and setting custom animations is currently not possible.
I was able to get it to work with a switch statement by wrapping the function that returns an AnyView
in a VStack
. I also had to give the AnyView
an .id
so SwiftUI can know when it changes. This is on Xcode 11.3 and iOS 13.3
struct EnumView: View {
@ObservedObject var viewModel: ViewModel
var body: some View {
VStack {
view(for: viewModel.viewState)
.id(viewModel.viewState)
.transition(.opacity)
}
}
func view(for viewState: ViewModel.ViewState) -> AnyView {
switch viewState {
case .loading:
return AnyView(LoadingStateView(viewModel: self.viewModel))
case .dataLoaded:
return AnyView(LoadedStateView(viewModel: self.viewModel))
case let .error(error):
return AnyView(ErrorView(error: error, viewModel: viewModel))
}
}
}
Also for my example in the ViewModel
I need to wrap the viewState
changes in a withAnimation
block
withAnimation {
self.viewState = .loading
}
In iOS 14 they added the possibility to use if let
and switch
statements in function builders. Maybe it helps for your issues:
https://www.hackingwithswift.com/articles/221/whats-new-in-swiftui-for-ios-14 (at the article's bottom)
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