ios - SwiftUI - 根据条件添加导航栏按钮

Question

鉴于我有这样的看法..

@State var tabIndex: Int = 0
           
 var body: some View {

  TabView(selection: $tabIndex)
  {
   Text("Tab 1").tabItem({
    Image(systemName: "message")
   }).tag(0)           
                
   Text("Tab 2").tabItem({
    Image(systemName: "arkit")
   }).tag(1)             
          
   Text("Tab 3").tabItem({
    Image(systemName: "battery.100")
   }).tag(2)
  }.navigationBarTitle("Tabbed View")
            
 }

这会产生这样的 View ，这是预期的:

向我可以使用的栏添加导航按钮

 .navigationBarItems(trailing:
  Button(action: {print("Button was tapped")}) {
   Image(systemName: "plus")
    .resizable().frame(width: 20, height: 20)
  })

它将按钮添加为 expected
有没有办法只根据条件添加(或显示)按钮？

if (self.tabIndex == 1){
  show button
}
else {
 don't show button
}

Answer 1

这是可能的方法

.navigationBarItems(trailing: self.tabIndex == 1 ? 
    AnyView(self.trailingButton) : AnyView(EmptyView()))

低于body

var trailingButton: some View {
  Button(action: {print("Button was tapped")}) {
   Image(systemName: "plus")
    .resizable().frame(width: 20, height: 20)
  }
}