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NavigationLink inside LazyVGrid cycles all entries on back, SwiftUI

Tags:

ios

swift

swiftui

I have an image grid. Each image on tap should push a view on the NavigationView with the image details.

The navigation link works as intended, but when I press the back button it opens the next image and so on until it has cycled all the images. What is going on?

This is the View:

struct ImageGrid: View {
    
    @ObservedObject var part: Part
    @State private var showingImagePicker = false
    @State private var inputImage: UIImage?
    var body: some View {
        Button("add images"){
            self.showingImagePicker = true
        }
        LazyVGrid(columns: [GridItem(.adaptive(minimum:100))]){
            ForEach(part.images){ image in
                ZStack {
                    Image(uiImage: image.thumb)
                        .resizable()
                        .scaledToFit()
                    NavigationLink (
                        destination: ImageDetail(image:image),
                        label: {
                            EmptyView()
                        }
                    ).buttonStyle(PlainButtonStyle())
                }
            }
        }
        .sheet(isPresented: $showingImagePicker, onDismiss: loadImage) {
            ImagePicker(image: self.$inputImage)
        }
        
    }
    // other functions ...
    ...
}

and this is the detail View

struct ImageDetail: View {
    
    @ObservedObject var image: TrainingImage
    var body: some View {
        VStack {
            Image(uiImage: image.content)
                .resizable()
                .scaledToFit()
        }
    }
}

EDIT:

This is a self-contained example isolating the behaviour. It seems to stop working correctly when the grid is inside a form section. Eliminating the form and the section the navigation link works correctly



import SwiftUI

extension String: Identifiable {
    public var id:Int {
        self.hashValue
    }
}

struct ImageDetail: View {
    
    var image: String
    var body: some View {
        VStack {
            Image(uiImage: UIImage(systemName: image)!)
                .resizable()
                .scaledToFit()
        }
    }
}

struct ContentView: View {
    @State var images:[String] = ["plus", "minus"]
    var body: some View {
        NavigationView {
            Form {
                Section {
                    LazyVGrid(columns: [GridItem(.adaptive(minimum:100))]){
                        ForEach(images){ image in
                            NavigationLink (
                                destination: ImageDetail(image: image),
                                label: {
                                    Image(uiImage: UIImage(systemName: image)!)
                                        .resizable()
                                        .scaledToFit()
                                }
                            ).buttonStyle(PlainButtonStyle())
                        }
                    }
                }
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

like image 706
Daniele Bernardini Avatar asked Oct 06 '20 17:10

Daniele Bernardini


1 Answers

It is Form/List feature to auto-detect links in rows, but you have several in row, so the effect. The solution would be to separate cell view and hide link from auto-detection.

Tested with Xcode 12.0 / iOS 14

struct ContentView: View {
    @State var images:[String] = ["plus", "minus"]
    var body: some View {
        NavigationView {
            Form {
                Section {
                    LazyVGrid(columns: [GridItem(.adaptive(minimum:100))]){
                        ForEach(images){
                                    ImageCellView(image: $0)
                        }
                    }
                }
            }
        }
    }
}

struct ImageCellView: View {
    var image: String
    @State private var isActive = false
    var body: some View {
        Image(uiImage: UIImage(systemName: image)!)
             .resizable()
             .scaledToFit()
            .onTapGesture {
                self.isActive = true
            }
        .background(
             NavigationLink (
                  destination: ImageDetail(image: image), isActive: $isActive,
                  label: {
                    EmptyView()
                  }
             ))
    }
}

backup

like image 61
Asperi Avatar answered Oct 03 '22 03:10

Asperi