Question

当EditMode更改时，我想执行一个操作。

具体地说，在编辑模式下，用户可以选择一些要删除的项目。他通常随后会按下垃圾桶按钮。但是他也可以按“完成”。当他以后再次按Edit时，仍会选择以前选择的项目。我希望清除所有物品。

struct ContentView: View {
    @State var isEditMode: EditMode = .inactive
    @State var selection = Set<UUID>()
    var items = [Item(), Item(), Item(), Item(), Item()]

    var body: some View {
        NavigationView {
            List(selection: $selection) {
                ForEach(items) { item in
                    Text(item.title)
                }
            }
            .navigationBarTitle(Text("Demo"))
            .navigationBarItems(
                leading: EditButton(),
                trailing: addDelButton
            )
            .environment(\.editMode, self.$isEditMode)
        }
    }

    private var addDelButton: some View {
        if isEditMode == .inactive {
            return Button(action: reset) {
                Image(systemName: "plus")
            }
        } else {
            return Button(action: reset) {
                Image(systemName: "trash")
            }
        }
    }

    private func reset() {
        selection = Set<UUID>()
    }
}

项目定义：

struct Item: Identifiable {
    let id = UUID()
    let title: String

    static var i = 0
    init() {
        self.title = "\(Item.i)"
        Item.i += 1
    }
}

Answer 1

@Casper为我指明了正确的方向。这是我想出的。该解决方案用一块石头抓到两只鸟：

在切换editMode时，整个视图会重新绘制
激活/停用editMode后可以执行特定操作

希望这对其他人有帮助。

struct ContentView: View {
    @State var editMode: EditMode = .inactive
    @State var selection = Set<UUID>()
    @State var items = [Item(), Item(), Item()]

    var body: some View {
        NavigationView {
            List(selection: $selection) {
                ForEach(items) { item in
                    Text(item.title)
                }
            }
            .navigationBarTitle(Text("Demo"))
            .navigationBarItems(
                leading: editButton,
                trailing: addDelButton
            )
            .environment(\.editMode, self.$editMode)
        }
    }

    private var editButton: some View {
        Button(action: {
            self.editMode.toggle()
            self.selection = Set<UUID>()
        }) {
            Text(self.editMode.title)
        }
    }

    private var addDelButton: some View {
        if editMode == .inactive {
            return Button(action: addItem) {
                Image(systemName: "plus")
            }
        } else {
            return Button(action: deleteItems) {
                Image(systemName: "trash")
            }
        }
    }

    private func addItem() {
        items.append(Item())
    }

    private func deleteItems() {
        for id in selection {
            if let index = items.lastIndex(where: { $0.id == id }) {
                items.remove(at: index)
            }
        }
        selection = Set<UUID>()
    }
}

extension EditMode {
    var title: String {
        self == .active ? "Done" : "Edit"
    }

    mutating func toggle() {
        self = self == .active ? .inactive : .active
    }
}

当EditMode更改时，SwiftUI如何执行动作？

1 个答案: