SwiftUI侧边栏不记得状态 [英] SwiftUI Sidebar doesn't remember state
问题描述
我有这个应用程序,它使用iOS14中针对iPad os引入的新侧边栏,但我不知道为什么它不记得隐藏时的状态
I Have this app that uses the new sidebar introduced in iOS14 for iPad os but I can't figure out why it doesn't remember the state when its hidden
这是侧边栏结构
import SwiftUI
struct Sidebar: View {
@Environment(\.managedObjectContext) var moc
@Binding var selection : Set<NavigationItem>
var body: some View {
List(selection: $selection) {
NavigationLink(destination: AgendaView().environment(\.managedObjectContext, moc).navigationTitle("Agenda"), label: {
Label("Agenda", systemImage: "book")
})
.tag(NavigationItem.agenda)
NavigationLink(destination: Text("Subjects"), label: {
Label("Materie", systemImage: "tray.full")
})
.tag(NavigationItem.subjects)
NavigationLink(destination: Text("Calendario"), label: {
Label("Calendario", systemImage: "calendar")
})
.tag(NavigationItem.calendar)
NavigationLink(destination: SettingsView().environment(\.managedObjectContext, moc).navigationTitle("Impostazioni"), label: {
Label("Impostazioni", systemImage: "gear")
})
.tag(NavigationItem.settings)
}
.listStyle(SidebarListStyle())
}
}
为了标记元素,我使用了一个名为NavigationItem的自定义结构
for tagging the elements I use a custom struct called NavigationItem
enum NavigationItem {
case agenda
case calendar
case ...
}
这是我在内容视图中放置侧边栏的位置,您可以看到该设备是否是iPad(使用sizeClasses检测到),我使用侧边栏,否则,如果是iPhone,则我使用TabBar
and here is where I placed the Sidebar in the content view, as you can see if the device is an iPad (detected using sizeClasses) I use the sidebar, otherwise if its an iPhone I use the TabBar
import SwiftUI
struct ContentView: View {
@Environment(\.horizontalSizeClass) var horizontalSizeClass
@Environment(\.managedObjectContext) var moc
@State private var selection : Set<NavigationItem> = [.agenda]
@ViewBuilder
var body: some View {
if horizontalSizeClass == .compact {
TabBar(selection: $selection)
.environment(\.managedObjectContext, moc)
} else {
NavigationView {
Sidebar(selection: $selection)
.environment(\.managedObjectContext, moc)
.navigationTitle("Menu")
}
}
}
}
推荐答案
List(selection: $selection)
仅用于macOS.看到标题中的以下注释:
List(selection: $selection)
for selection binding is macOS only. See this comment in the header:
/// On iOS and tvOS, you must explicitly put the list into edit mode for
/// the selection to apply.
作为解决方法,您可以使之前选择的行显示为粗体,例如
As a workaround you could make the previously selected row appear bold, e.g.
NavigationLink(
destination: HomeView(),
tag: Screen.home,
selection: $selection,
label: {
Label("Home", systemImage: "house" )
})
.font(Font.headline.weight(selection == Screen.home ? .bold : .regular))
有关更多信息,请参见 answer .
For more see this answer.
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