[英]Navigation Bar Items with @EnvironmentObject
我想使用 SwiftUI 創建一個Settings
視圖。 我主要是拿蘋果官方關於SwiftUI的例子來實現我的代碼。 設置視圖應該可以切換是否顯示我的收藏夾項目。
現在我有一個地標列表和一個設置視圖。
struct Landmark: Hashable, Codable, Identifiable {
var id: Int
var imageName: String
var title: String
var isFavorite: Bool
var description: String
enum CodingKeys: String, CodingKey {
case id, imageName, title, description
}
}
final class UserData: ObservableObject {
@Published var showFavoriteOnly: Bool = false
@Published var items: [Landmark] = landmarkData
@Published var showProfile: Bool = false
}
struct ItemList: View {
@EnvironmentObject var userData: UserData
@State var trailing: Bool = false
init() {
UITableView.appearance().separatorStyle = .none
}
var body: some View {
NavigationView {
List {
VStack {
CircleBadgeView(text: String(landmarkData.count), thickness: 2)
Text("Tutorials available")
}.frame(minWidth:0, maxWidth: .infinity)
ForEach(userData.items) { landmark in
if !self.userData.showFavoriteOnly || landmark.isFavorite {
ZStack {
Image(landmark.imageName)
.resizable()
.frame(minWidth: 0, maxWidth: .infinity)
.cornerRadius(10)
.overlay(ImageOverlay(text: landmark.title), alignment: .bottomTrailing)
Text(String(landmark.isFavorite))
NavigationLink(destination: TutorialDetailView(landmark: landmark)) {
EmptyView()
}.buttonStyle(PlainButtonStyle())
}
}
}
}.navigationBarTitle("Tutorials")
.navigationBarItems(trailing: trailingItem())
}
}
}
extension ItemList {
func trailingItem () -> some View {
return HStack {
if userData.showProfile {
NavigationLink(destination: ProfileView()) {
Image(systemName: "person.circle")
.imageScale(.large)
.accessibility(label: Text("Profile"))
}
}
NavigationLink(destination: SettingsView().environmentObject(userData)) {
Image(systemName: "gear")
.imageScale(.large)
.accessibility(label: Text("Settings"))
}
}
}
}
如您所見,可以從我的 NavigationView 的navigationBarItems
訪問我的SettingsView
。 我不知道這是否是問題所在,但是當我將 Toggle 放入ListView
它會按預期工作。 但是現在當我觸發切換以僅啟用最喜歡的應用程序時,我的應用程序會立即崩潰。
我試圖從SettingsView
觸發Show profile
切換並且它有效。
struct SettingsView: View {
@EnvironmentObject var userData: UserData
var body: some View {
Form {
Section(header: Text("General")) {
Toggle(isOn: $userData.showProfile) {
Text("Show profile")
}
Toggle(isOn: $userData.showFavoriteOnly) {
Text("Favorites only")
}
}
Section(header: Text("UI")) {
Toggle(isOn: .constant(false)) {
Text("Dark mode")
}
NavigationLink(destination: Text("third")) {
Text("Third navigation")
}
}
}.navigationBarTitle(Text("Settings"), displayMode: .inline)
}
}
簡而言之,當我觸發Show only favorite
Toggle 時,崩潰出現在我的SettingsView
,然后我嘗試返回上一個視圖,即ItemListView
我能得到的關於錯誤的唯一信息是Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
你可以在我的 GitHub 上找到整個項目: https : //github.com/Hurobaki/swiftui-tutorial
一些幫助將不勝感激:)
這是您的示例代碼的最小版本,它有效:
struct Landmark: Hashable, Codable, Identifiable {
var id: Int
var imageName: String
var title: String
var isFavorite: Bool
var description: String
}
final class UserData: ObservableObject {
@Published var showFavoriteOnly: Bool = false
@Published var items: [Landmark] = [
Landmark(id: 1, imageName: "a", title: "a", isFavorite: true, description: "A"),
Landmark(id: 2, imageName: "b", title: "b", isFavorite: false, description: "B")
]
}
struct ContentView: View {
@EnvironmentObject var userData: UserData
var body: some View {
NavigationView {
List(userData.items.filter { !userData.showFavoriteOnly || $0.isFavorite }) { landmark in
Text(String(landmark.isFavorite))
}
.navigationBarTitle("Tutorials")
.navigationBarItems(trailing: trailingItem())
}
}
func trailingItem () -> some View {
return HStack {
NavigationLink(destination: SettingsView()) {
Text("Settings")
}
}
}
}
struct SettingsView: View {
@EnvironmentObject var userData: UserData
var body: some View {
Form {
Section(header: Text("General")) {
Toggle(isOn: $userData.showFavoriteOnly) {
Text("Favorites only")
}
}
}.navigationBarTitle(Text("Settings"), displayMode: .inline)
}
}
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