Why does my TabView change back to Home tab when image loads? - uiimage

Question

I created a TabView with two tabs. One is Home and the other loads text and an image from NASA pic of the day API. When I change to the NASA pic of the day, I see "Loading data" until the data loads. Once the data is loaded, for some reason the tab switches back to the "Home" tab. After this bug happens, I can switch back and forth between the two tabs normally and everything is loaded. Why does the tab get switched back to the home tab? Thank you!!
APIImageView Code:
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()
}
}
APIImage Code:
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
}
}
}
MainTabView Code:
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

Maybe not directly a solution, but also important: it seems that the MainTabView is not entirely correct (the .tag() should be outside the .tabItem closure). This would be a correct version:
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()
}
}
Maybe this is already the solution; if not, I hope it is still helpful! :)