关于属性更改的SwiftUI动画？

我想在列表中设置项目外观的动画。列表如下所示：

Text("Jim")
Text("Jonas")
TextField("New Player")
TextField("New Player") //should be animated when appearing (not shown until a name is typed in the first "New Player")

最后一个

TextField

应该隐藏到

newPersonName.count>0

之后，再显示动画

代码如下：

struct V_NewSession: View {
    @State var newPersonName: String = ""
    @State var participants: [String] = [
        "Jim",
        "Jonas"
    ]
    var body: some View {
        VStack(alignment: .leading) {
            ForEach(0...self.participants.count + 1, id: \.self) { i in
                // Without this if statement, the animation works
                // but the Textfield shouldn't be shown until a name is typed
                if (!(self.newPersonName.count == 0 && i == self.participants.count + 1)) {
                    HStack {
                        if(i < self.participants.count) {
                            Text(self.participants[i])
                        } else {
                            TextField("New Player",
                                      text: $newPersonName,
                                      onEditingChanged: { focused in
                                if (self.newPersonName.count == 0) {
                                    if (!focused) {
                                        handleNewPlayerEntry()
                                    }
                                }
                           })
                        }
                    }
                }
            }
            .transition(.scale)
            Spacer()
            }
    }
    
    func handleNewPlayerEntry() {
        if(newPersonName.count > 0) {
            withAnimation(.spring()) {
                participants.append(newPersonName)
                newPersonName = ""
            }
        }
    }
}

struct V_NewSession:View{
@状态变量newPersonName:String=“”
@状态变量参与者：[字符串]=[
“吉姆”，
“乔纳斯”
]
var body：一些观点{
VStack（对齐：。前导）{
ForEach（0…self.participants.count+1，id:\.self）{i in
//如果没有此if语句，动画将正常工作
//但文本字段在输入名称之前不应显示
if（！（self.newPersonName.count==0&&i==self.participants.count+1））{
HStack{
如果（i0）{
使用动画（.spring（））{
参与者。追加（newPersonName）
newPersonName=“”
}
}
}
}

我知道

with animation（…）

仅适用于

参与者。append（newPersonName）

，但如何让动画处理if语句中的属性更改？

---

如果（！（self.newPersonName.count==0&&i==self.particients.count+1））.animation（）不起作用。
这是您试图构建的吗

struct ContentView: View {
    @State var newPersonName: String = ""
    @State var participants: [String] = [
        "Jim",
        "Jonas"
    ]
    @State var editingNewPlayer = false

    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            ForEach(participants, id: \.self) { participant in
                Text(participant)
                    .padding(.trailing)
                Divider()
            }
        
            Button(action: handleNewPlayerEntry, label: {
                TextField("New Player", text: $newPersonName, onEditingChanged: { edit in
                    editingNewPlayer = edit
                }, onCommit: handleNewPlayerEntry)
            })
        
            if editingNewPlayer {
                Button(action: handleNewPlayerEntry, label: {
                    TextField("New Player", text: $newPersonName) { edit in
                        editingNewPlayer = false
                    }
                })
            }
        }
        .padding(.leading)
        .frame(maxHeight: .infinity, alignment: .top)
        .transition(.opacity)
        .animation(.easeIn)
    }

    func handleNewPlayerEntry() {
        if newPersonName.count > 0 {
            withAnimation(.spring()) {
                participants.append(newPersonName)
                newPersonName = ""
                editingNewPlayer = false
            }
        }
    }
}

我无法编译您的示例代码，但下面是一个在ViewModel中使用Combine来控制是否根据条件显示第二个
TextField
：


import SwiftUI
import Combine

class ViewModel : ObservableObject {
    @Published var textFieldValue1 = ""
    @Published var textFieldValue2 = "Second field"
    @Published var showTextField2 = false
    
    private var cancellable : AnyCancellable?
    
    init() {
        cancellable = $textFieldValue1.sink { value in
            withAnimation {
                self.showTextField2 = !value.isEmpty
            }
        }
    }
}

struct ContentView: View {
    @StateObject var viewModel = ViewModel()
    
    var body: some View {
        VStack {
            TextField("", text: $viewModel.textFieldValue1)
                .textFieldStyle(RoundedBorderTextFieldStyle())
            if viewModel.showTextField2 {
                TextField("", text: $viewModel.textFieldValue2)
                    .textFieldStyle(RoundedBorderTextFieldStyle())
                    .transition(.scale)
            }
        }
    }
}

我更新了它，现在它可以编译了，正在运行，谢谢：）