SwiftUI 工作表不更新变量答案

【问题标题】：SwiftUI Sheet not updating variableSwiftUI 工作表不更新变量
【发布时间】：2020-05-14 08:44:28
【问题描述】：

如果我通过选择另一个项目来更改值，我正在尝试将一个项目传递给工作表。工作表一直显示第一项，即使我从未使用第一项调用工作表。

这是一个错误还是我做错了什么？

锻炼列表.swift

import SwiftUI

struct WorkoutList: View {
    private var workouts = workoutData
    @State var showWorkoutDetails = false

    var body: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 20) {
                ForEach(workouts) { workoutCard in
                    GeometryReader { geometry in
                        Button(action: {self.showWorkoutDetails.toggle()}) {
                            WorkoutCardView(workout: workoutCard)
                                .rotation3DEffect(Angle(degrees: Double((geometry.frame(in: .global).minX - 30) / -30)), axis: (x: 0, y: 10, z: 0))
                                .sheet(isPresented: self.$showWorkoutDetails) {
                                    WorkoutDetails(workout: workoutCard)
                                }
                        }
                    }
                    .frame(width:246, height: 360)

                }
            }
        .padding(30)
        }
    }
}

private let workoutData = [
    Workout(name: "Workout #1", imageName: "workoutImage", color: Color.orange),
    Workout(name: "Workout #2", imageName: "workoutImage", color: Color.green),
    Workout(name: "Workout #3", imageName: "workoutImage", color: Color.red),
    Workout(name: "Workout #4", imageName: "workoutImage", color: Color.blue)
]

WorkoutDetails.swift

import SwiftUI

struct WorkoutDetails: View {
    var workout = Workout(name: "", imageName: "", color: Color.black)

    var body: some View {
        GeometryReader { geometry in
            ZStack {
                Rectangle()
                    .fill(self.workout.color)

                VStack(alignment: .leading) {
                    VStack(alignment: .leading) {
                        Text(self.workout.name)
                            .foregroundColor(.white)
                            .font(.title)
                            .fontWeight(.heavy)
                            .lineLimit(nil)
                            .frame(minWidth: 0, maxWidth: .infinity, alignment: .leading)
                            .frame(height: 70)
                    }
                    .frame(width: 180)

                    Image(self.workout.imageName)
                        .resizable()
                        .aspectRatio(contentMode: .fit)
                        .frame(width: geometry.size.width-60, height: 200)
                        .padding()

                    Spacer()
                }
                .padding(.top, 40)
                .padding(.leading, 10)
            }
        }
        .edgesIgnoringSafeArea(.bottom)
    }
}

我想在这里显示锻炼。但无论我改变它，我总是得到“锻炼#1”，我不知道我做错了什么。

【问题讨论】：

标签： swift swiftui

【解决方案1】：

使用可选锻炼创建绑定。 Nil 将是不显示工作表的情况，将锻炼分配给此变量会显示相应的工作表。

struct WorkoutList: View {
  private var workouts = workoutData
  @State var selectedWorkout: Workout?

  var body: some View {
    ScrollView(.horizontal, showsIndicators: false) {
      HStack(spacing: 20) {
        ForEach(workouts) { workoutCard in
          GeometryReader { geometry in
            Button(action: { self.selectedWorkout = workoutCard }) {
              WorkoutCardView(workout: workoutCard).rotation3DEffect(Angle(degrees: Double((geometry.frame(in: .global).minX - 30) / -30)), axis: (x: 0, y: 10, z: 0)).sheet(item: self.$selectedWorkout) { workout in
                WorkoutDetails(workout: workout)
              }
            }
          }.frame(width:246, height: 360) 
        }
      }.padding(30)
    }
  }
}

【讨论】：

【解决方案2】：

我有类似的问题。您想将锻炼卡分配给 @State 和内部 .sheet 有一些逻辑来决定要显示什么视图

这里有更多关于你的问题：Multiple sheet(isPresented:) doesn't work in SwiftUI

【讨论】：

【解决方案3】：

基本上我们需要在点击按钮时存储selectedWorkout。

@State var isDetailPresented = false
@State var selectedWorkout: Workout?

...

Button(action: {
    self.selectedWorkout = workoutCard
    self.isDetailPresented.toggle()
}, label: {
    //Your view here
}).buttonStyle(PlainButtonStyle())
  .sheet(isPresented: $isDetailPresented) {
    WorkoutDetails(workout: self.selectedWorkout!)
}
...

【讨论】：

【解决方案4】：

传递绑定而不是 @State 变量的值

在工作表中包含的视图主体中使用 Binding 的值

struct WorkoutList: View {
    @State var isDetailPresented = false
    @State var selectedWorkout: Workout?

    var body: some View {
        Button(action: {
            self.selectedWorkout = workouts[yourIndex]
            self.showWorkoutDetails.toggle()
        }) {
            Text("Test")
        }
        .sheet(isPresented: self.$showWorkoutDetails) {
            WorkoutDetails(workout: selectedWorkout)
        }
    }
}
struct WorkoutDetails: View {
    @Binding var workout: Workout?

    var body: some View {
        ZStack {
            Rectangle()
                .fill(self.workout.color)
            // your code
        }
    }
}

【讨论】：

【解决方案5】：

我认为这里解释得更好 SwiftUI sheet doesn't access the latest value of state variables on first appearance

struct DemoView: View {
  @State var showDetails: Bool = false
  var body: some View {
    VStack {
        Button(action: {
          showDetails = true
        }) {
            Text("Show sheet")
        }
    }.sheet(isPresented: $showDetails){
        SheetDetailView(flag: $showDetails)
    }
  }
}

struct SheetDetailView: View {
  @Binding var flag: Bool
     var body: some View {
       VStack {
          Text("showDetails: \(flag ? "yes" : "no")")
           }
     }
}

只需在表单视图绑定中制作参数，并发送绑定参数，您仍然可以保留布尔切换。

【讨论】：