SwiftUI：如何使用 ForEach select 多个项目（图像）？

Question

我正在开发具有 select 多个缩略图块功能的项目。只有 selected 缩略图/图像将突出显示。对于 ChildView，如果使用点击图像，绑定 activeBlock 应该被打开 true/false。但是，当我 select 一个缩略图时，所有的缩略图都会 highlighted.I 想出一些想法 like

@State var selectedBlocks:[Bool] 
// which should contain wether or not a certain block is selected.

但是不知道怎么实现。

这是我的代码：

子视图

@Binding var activeBlock:Bool
var thumbnail: String
var body: some View {
    VStack {
        ZStack {
            Image(thumbnail)
               .resizable()
               .frame(width: 80, height: 80)
                    .background(Color.black)
                    .cornerRadius(10)
            if activeBlock {
               RoundedRectangle(cornerRadius: 10)
                    .stroke(style: StrokeStyle(lineWidth: 2))
                    .frame(width: 80, height: 80)
                    .foregroundColor(Color("orange"))           
            }
        }
}

BlockBView

struct VideoData: Identifiable{
    var id = UUID()
    var thumbnails: String
}

struct BlockView: View {
        var videos:[VideoData] = [
        VideoData(thumbnails: "test"), VideoData(thumbnails: "test2"), VideoData(thumbnails: "test1")
    ]
    
    @State var activeBlock = false

    var body: some View {
        ScrollView(.horizontal){
                HStack {
                    ForEach(0..<videos.count) { _ in
                        Button(action: {
                            self.activeBlock.toggle()
                        }, label: {
                            
                            ChildView(activeBlock: $activeBlock, thumbnail: "test")  
                        })           
                    }
                }                
            }
}

感谢您的帮助！

Answer 1

这是一个可能的方法演示 - 我们通过视频计数初始化 Bool 数组，并通过索引将激活标志传递到子视图中。

使用 Xcode 12.1 / iOS 14.1 测试（带有一些复制代码）

struct BlockView: View {
    var videos:[VideoData] = [
        VideoData(thumbnails: "flag-1"), VideoData(thumbnails: "flag-2"), VideoData(thumbnails: "flag-3")
    ]
    
    @State private var activeBlocks: [Bool]    // << declare
    
    init() {
        // initialize state with needed count of bools
        self._activeBlocks = State(initialValue: Array(repeating: false, count: videos.count))
    }
    
    var body: some View {
        ScrollView(.horizontal){
            HStack {
                ForEach(videos.indices, id: \.self) { i in
                    Button(action: {
                        self.activeBlocks[i].toggle()       // << here !!
                    }, label: {
                        ChildView(activeBlock: activeBlocks[i],       // << here !!
                                  thumbnail: videos[i].thumbnails)
                    })
                }
            }
        }
    }
}

struct ChildView: View {
    var activeBlock:Bool       // << value, no binding needed
    var thumbnail: String
    
    var body: some View {
        VStack {
            ZStack {
                Image(thumbnail)
                    .resizable()
                    .frame(width: 80, height: 80)
                    .background(Color.black)
                    .cornerRadius(10)
                if activeBlock {
                    RoundedRectangle(cornerRadius: 10)
                        .stroke(style: StrokeStyle(lineWidth: 2))
                        .frame(width: 80, height: 80)
                        .foregroundColor(Color.orange)
                }
            }
        }
    }
}

Answer 2

最终结果

首先构建您的元素和模型。我正在使用 MVVM，

 class RowModel : ObservableObject, Identifiable {
     @Published var isSelected = false
     @Published var thumnailIcon: String
     @Published var name: String

     var id : String

     var cancellables = Set<AnyCancellable>()

     init(id: String, name: String, icon: String) {
         self.id = id
         self.name = name
         self.thumnailIcon = icon
     }
 }

 //Equivalent to your BlockView
 struct Row : View {
     @ObservedObject var model: RowModel

     var body: some View {
         GroupBox(label:
             Label(model.name, systemImage: model.thumnailIcon)
                 .foregroundColor(model.isSelected ? Color.orange : .gray)
         ) {
             HStack {
                 Capsule()
                     .fill(model.isSelected ? Color.orange : .gray)
                     .onTapGesture {
                         model.isSelected = !model.isSelected
                     }

                 //Two way binding
                 Toggle("", isOn: $model.isSelected)
             }

         }.animation(.spring())
     }
 }

在您的父视图中准备数据和处理操作

 struct ContentView: View {
     private let layout = [GridItem(.flexible()),GridItem(.flexible())]

     @ObservedObject var model = ContentModel()

     var body: some View {
         VStack {
             ScrollView {
                 LazyVGrid(columns: layout) {
                     ForEach(model.rowModels) { model in
                         Row(model: model)
                     }
                 }
             }

             if model.selected.count > 0 {
                 HStack {
                     Text(model.selected.joined(separator: ", "))
                     Spacer()
                     Button(action: {
                         model.clearSelection()
                     }, label: {
                         Text("Clear")
                     })
                 }
             }
         }
         .padding()
         .onAppear(perform: prepare)
     }

     func prepare() {
         model.prepare()
     }
 }

 class ContentModel: ObservableObject {
     @Published var rowModels = [RowModel]()

     //I'm handling by ID for futher use
     //But you can convert to your Array of Boolean
     @Published var selected = Set<String>()

     func prepare() {
         for i in 0..<20 {
             let row = RowModel(id: "\(i)", name: "Block \(i)", icon: "heart.fill")

             row.$isSelected
                 .removeDuplicates()
                 .receive(on: RunLoop.main)
                 .sink(receiveValue: { [weak self] selected in
                     guard let `self` = self else { return }
                     print(selected)
                     if selected {
                         self.selected.insert(row.name)
                     }else{
                         self.selected.remove(row.name)
                     }
                 }).store(in: &row.cancellables)

             rowModels.append(row)
         }
     }

     func clearSelection() {
         for r in rowModels {
             r.isSelected = false
         }
     }
 }

不要忘记 import Combine 框架。

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