CODEWITHSUNDEEP
iosswiftswiftui
SwiftedMind
SwiftedMind

Reputation: 4287

SwiftUI - Animations triggered inside a View that's in a list doesn't animate the list as well

I have a List that's displaying two Views of the same type. When you tap on one of the views, they change their height with an animation.

However, the List those views are embedded in doesn't animate which results in an ugly glitch because the height of the List row changes instantly, while the actual view inside that row is animated:

enter image description here

How can I make the List animate as well? I tried addinga .animation modifier to it but that doesn't do anything.

I also don't want to move the tapGesture out of the view. The view should be self-contained and not rely on some other view to control it (I think that's what MVVM is about)

thanks!

import SwiftUI

struct SubView: View {
    @State var change: Bool = false

    var body: some View {
        Rectangle()
            .frame(width: 200, height: change ? 300 : 200)
            .foregroundColor(Color.red)
            .onTapGesture {
                withAnimation {
                    self.change.toggle()
                }
        }
    }
}

struct Test: View {

    var body: some View {
        List {
            SubView()
            SubView()
        }
    }
}

struct Test_Previews: PreviewProvider {
    static var previews: some View {
        Test()
    }
}

Upvotes: 20

Views: 4883

Answers (2)

Aitor Pagán
Aitor Pagán

Reputation: 423

I recently found that embedding your row view within a ScrollView will apply your desired animation without making that weird List animation for height calculation, for instance:

import SwiftUI

struct SubView: View {
    @State var change: Bool = false

    var body: some View {
        Rectangle()
            .frame(width: 200, height: change ? 300 : 200)
            .foregroundColor(Color.red)
            .onTapGesture {
                withAnimation {
                    self.change.toggle()
                }
        }
    }
}

struct Test: View {

    var body: some View {
        List {
            ScrollView { SubView() }
            ScrollView { SubView() }
        }
    }
}

struct Test_Previews: PreviewProvider {
    static var previews: some View {
        Test()
    }
}

Upvotes: 0

Asperi
Asperi

Reputation: 257711

The solution is just to make height animatable continuously, by providing explicit animatable modifier for this.

Here is working approach. Tested with Xcode 11.4 / iOS 13.4.

demo

Implementation of simple helper modifier

struct AnimatingCellHeight: AnimatableModifier {
    var height: CGFloat = 0

    var animatableData: CGFloat {
        get { height }
        set { height = newValue }
    }

    func body(content: Content) -> some View {
        content.frame(height: height)
    }
}

Modified using view (other parts unchanged)

struct SubView: View {
    @State var change: Bool = false

    var body: some View {
        Rectangle()
            .frame(width: 200)
            .modifier(AnimatingCellHeight(height: change ? 300 : 200))
            .foregroundColor(Color.red)
            .onTapGesture {
                withAnimation {
                    self.change.toggle()
                }
            }
    }
}

Upvotes: 25

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