为什么加载图像时，我的TabView会变回"主页"选项卡

Question

我创建了一个带有两个选项卡的TabView。一个是Home，另一个加载来自NASA当天API图片的文本和图像。当我切换到NASA当天的图片时，我会看到"加载数据"，直到数据加载。数据加载后，由于某种原因，选项卡会切换回"主页"选项卡。发生此错误后，我可以正常地在两个选项卡之间来回切换，所有内容都已加载。为什么选项卡会切换回主页选项卡？非常感谢。

APIImageView代码：

import SwiftUI
struct ApiImageView: View {
@ObservedObject var apiImage = ApiImage()
var body: some View {
Group {
if apiImage.dataHasLoaded {
VStack {
Text(apiImage.title!)
.font(.largeTitle)
Image(uiImage: apiImage.image!).resizable()
.cornerRadius(10)
.padding()
ScrollView(.vertical, showsIndicators: false) {
Text(apiImage.explanation!)
.font(.subheadline)
.padding()
}
}
} else {
Text("Loading Data")
}
}.onAppear {
self.apiImage.loadImageFromApi(urlString: "https://api.nasa.gov/planetary/apod?api_key=eaRYg7fgTemadUv1bQawGRqCWBgktMjolYwiRrHK")
}
}
}
struct ApiImageView_Previews: PreviewProvider {
static var previews: some View {
ApiImageView()
}
}

API图像代码：

import SwiftUI
class ApiImage: ObservableObject {
@Published var dataHasLoaded = false
@Published var image: UIImage? = nil
@Published var title: String? = nil
@Published var explanation: String? = nil
}
extension ApiImage {
func loadImageFromApi(urlString: String) {
let url = URL(string: urlString)!
var request = URLRequest(url: url)
request.httpMethod = "GET"
let task = URLSession.shared.dataTask(with: request, completionHandler: parseJsonObject)
task.resume()
}
func parseJsonObject(data: Data?, urlResponse: URLResponse?, error: Error?) {
guard error == nil else {
print("(error!)")
return
}
guard let content = data else {
print("No data")
return
}
let json = try! JSONSerialization.jsonObject(with: content)
let jsonmap = json as! [String : Any]
let titleText = jsonmap["title"] as! String
let explanationText = jsonmap["explanation"] as! String
let urlString = jsonmap["url"] as! String
print("(urlString)")
print("(titleText)")
print("(explanationText)")
DispatchQueue.main.async {
self.title = titleText
self.explanation = explanationText
}
let url = URL(string: urlString)!
var request = URLRequest(url: url)
request.httpMethod = "GET"
let task = URLSession.shared.dataTask(with: request, completionHandler: setImageFromData)
task.resume()
}
func setImageFromData(data: Data?, urlResponse: URLResponse?, error: Error?) {
guard error == nil else {
print("(error!)")
return
}
guard let content = data else {
print("No data")
return
}
DispatchQueue.main.async {
self.image = UIImage(data: content)
self.dataHasLoaded = true
}
}
}

主选项卡视图代码：

import SwiftUI
struct MainTabView: View {
var body: some View {
TabView {
CategoryHome()
.tabItem {
Image(systemName: "house.fill")
Text("Landmarks")
.tag(0)
}
ApiImageView()
.tabItem {
Image(systemName: "flame.fill")
Text("NASA Pic")
//.tag(1)

}
}
}
}
struct MainTabView_Previews: PreviewProvider {
static var previews: some View {
MainTabView()
}
}

Answer 1

也许不是一个直接的解决方案，但也很重要：MainTabView似乎并不完全正确(.tag()应该在.tabItem闭包之外(。这将是一个正确的版本：

import SwiftUI
struct MainTabView: View {
var body: some View {
TabView {
CategoryHome()
.tabItem {
Image(systemName: "house.fill")
Text("Landmarks")
}.tag(0)
ApiImageView()
.tabItem {
Image(systemName: "flame.fill")
Text("NASA Pic")
}.tag(1)
}
}
}
struct MainTabView_Previews: PreviewProvider {
static var previews: some View {
MainTabView()
}
}

也许这已经是解决方案；如果没有，我希望它仍然有帮助！：(