Can't preview SwiftUI Canvas with RealityKit scene - swift

Question

I only create a new property of RealityKit.
Xcode won't be able to preview the SwiftUI canvas.
But it can build successfully.
I create the App by Xcode.
Choose Augmented Reality App and set User Interface to SwiftUI.
The project can work normally.
import SwiftUI
import RealityKit
struct ContentView : View {
var body: some View {
return VStack {
Text("123")
ARViewContainer().edgesIgnoringSafeArea(.all)
}
}
}
struct ARViewContainer: UIViewRepresentable {
func makeUIView(context: Context) -> ARView {
let arView = ARView(frame: .zero)
// Load the "Box" scene from the "Experience" Reality File
let boxAnchor = try! Experience.loadBox()
// Add the box anchor to the scene
arView.scene.anchors.append(boxAnchor)
return arView
}
func updateUIView(_ uiView: ARView, context: Context) {}
}
#if DEBUG
struct ContentView_Previews : PreviewProvider {
static var previews: some View {
ContentView()
}
}
#endif
I only create a new property of RealityKit in makeUIView function.
let test: AnchoringComponent.Target.Alignment = .horizontal
The project cannot preview canvas and appear the error
'Alignment' is not a member type of 'AnchoringComponent.Target'
The project still can compile successful.
I am so confused what I met.
Has anyone meet the same issue?

Answer 1

You have to fix several issues:
You can't use anchoring component in iOS Simulator or in SwiftUI Canvas Preview, because it can only be used for pinning a virtual content to the real world surfaces. So no simulator for AR apps.
RealityKit Anchors are useless in iOS Simulator mode and SwiftUI Canvas Preview mode.
// Use it only for compiled AR app, not simulated...
let _: AnchoringComponent.Target.Alignment = .horizontal
Not only anchors are useless in iOS Simulator Mode and SwiftUI Preview Mode but also other session-oriented properties (including ARView.session) like ones you can see on a picture:
Change .backgroundColor in ARView to any other desirable one. Default color sometimes doesn't allow you to see a RealityKit scene. Looks like a bug.
func makeUIView(context: Context) -> ARView {
let arView = ARView(frame: .zero)
let boxAnchor = try! Experience.loadBox()
boxAnchor.steelBox?.scale = SIMD3(5, 5, 5)
boxAnchor.steelBox?.orientation = simd_quatf(angle: Float.pi/4, axis: SIMD3(1,1,0))
arView.backgroundColor = .orange
arView.scene.anchors.append(boxAnchor)
return arView
}
And here's what you can see in SwiftUI Preview Area now:
And, of course, you have to give a Camera Permission before using AR app. And it doesn't matter what you're using: Storyboard or SwiftUI.
You need to add Camera Usage Description property and arkit string in info.plist file:
XML version looks like this:
/* info.plist
<key>NSCameraUsageDescription</key>
<string>Camera access for AR experience</string>
<key>UIRequiredDeviceCapabilities</key>
<array>
<string>armv7</string>
<string>arkit</string>
</array>
*/
After fixing these issues app compiles and works as expected (without any errors):