Apple ARKitVision示例在ViewController.swift文件中具有以下声明:
// The view controller that displays the status and "restart experience" UI.
private lazy var statusViewController: StatusViewController = {
return children.lazy.compactMap({ $0 as? StatusViewController }).first!
}()
但是，如果我复制相同的视图和源文件并将它们合并到另一个测试情节提要/项目中，则会收到错误消息“实例成员'children'不能用于'StatusViewController'类型”
那么，为什么这在ARKitVision示例中起作用，但是如果我从头开始进行设置却不起作用？ ARKitVision示例还需要做什么才能使它正常工作？谢谢😊
StatusViewController的完整类定义为:
/*
See LICENSE folder for this sample’s licensing information.
Abstract:
Utility class for showing messages above the AR view.
*/
import Foundation
import ARKit
/**
Displayed at the top of the main interface of the app that allows users to see
the status of the AR experience, as well as the ability to control restarting
the experience altogether.
- Tag: StatusViewController
*/
class StatusViewController: UIViewController {
// MARK: - Types
enum MessageType {
case trackingStateEscalation
case planeEstimation
case contentPlacement
case focusSquare
static var all: [MessageType] = [
.trackingStateEscalation,
.planeEstimation,
.contentPlacement,
.focusSquare
]
}
// MARK: - IBOutlets
@IBOutlet weak private var messagePanel: UIVisualEffectView!
@IBOutlet weak private var messageLabel: UILabel!
@IBOutlet weak private var restartExperienceButton: UIButton!
// MARK: - Properties
/// Trigerred when the "Restart Experience" button is tapped.
var restartExperienceHandler: () -> Void = {}
/// Seconds before the timer message should fade out. Adjust if the app needs longer transient messages.
private let displayDuration: TimeInterval = 6
// Timer for hiding messages.
private var messageHideTimer: Timer?
private var timers: [MessageType: Timer] = [:]
// MARK: - Message Handling
func showMessage(_ text: String, autoHide: Bool = true) {
// Cancel any previous hide timer.
messageHideTimer?.invalidate()
messageLabel.text = text
// Make sure status is showing.
setMessageHidden(false, animated: true)
if autoHide {
messageHideTimer = Timer.scheduledTimer(withTimeInterval: displayDuration, repeats: false, block: { [weak self] _ in
self?.setMessageHidden(true, animated: true)
})
}
}
func scheduleMessage(_ text: String, inSeconds seconds: TimeInterval, messageType: MessageType) {
cancelScheduledMessage(for: messageType)
let timer = Timer.scheduledTimer(withTimeInterval: seconds, repeats: false, block: { [weak self] timer in
self?.showMessage(text)
timer.invalidate()
})
timers[messageType] = timer
}
func cancelScheduledMessage(`for` messageType: MessageType) {
timers[messageType]?.invalidate()
timers[messageType] = nil
}
func cancelAllScheduledMessages() {
for messageType in MessageType.all {
cancelScheduledMessage(for: messageType)
}
}
// MARK: - ARKit
func showTrackingQualityInfo(for trackingState: ARCamera.TrackingState, autoHide: Bool) {
showMessage(trackingState.presentationString, autoHide: autoHide)
}
func escalateFeedback(for trackingState: ARCamera.TrackingState, inSeconds seconds: TimeInterval) {
cancelScheduledMessage(for: .trackingStateEscalation)
let timer = Timer.scheduledTimer(withTimeInterval: seconds, repeats: false, block: { [unowned self] _ in
self.cancelScheduledMessage(for: .trackingStateEscalation)
var message = trackingState.presentationString
if let recommendation = trackingState.recommendation {
message.append(": \(recommendation)")
}
self.showMessage(message, autoHide: false)
})
timers[.trackingStateEscalation] = timer
}
// MARK: - IBActions
@IBAction private func restartExperience(_ sender: UIButton) {
restartExperienceHandler()
}
// MARK: - Panel Visibility
private func setMessageHidden(_ hide: Bool, animated: Bool) {
// The panel starts out hidden, so show it before animating opacity.
messagePanel.isHidden = false
guard animated else {
messagePanel.alpha = hide ? 0 : 1
return
}
UIView.animate(withDuration: 0.2, delay: 0, options: [.beginFromCurrentState], animations: {
self.messagePanel.alpha = hide ? 0 : 1
}, completion: nil)
}
}
extension ARCamera.TrackingState {
var presentationString: String {
switch self {
case .notAvailable:
return "TRACKING UNAVAILABLE"
case .normal:
return "TRACKING NORMAL"
case .limited(.excessiveMotion):
return "TRACKING LIMITED\nExcessive motion"
case .limited(.insufficientFeatures):
return "TRACKING LIMITED\nLow detail"
case .limited(.initializing):
return "Initializing"
case .limited(.relocalizing):
return "Recovering from interruption"
}
}
var recommendation: String? {
switch self {
case .limited(.excessiveMotion):
return "Try slowing down your movement, or reset the session."
case .limited(.insufficientFeatures):
return "Try pointing at a flat surface, or reset the session."
case .limited(.relocalizing):
return "Return to the location where you left off or try resetting the session."
default:
return nil
}
}
}
ViewController类的定义是:
/*
See LICENSE folder for this sample’s licensing information.
Abstract:
Main view controller for the ARKitVision sample.
*/
import UIKit
import SpriteKit
import ARKit
import Vision
class ViewController: UIViewController, UIGestureRecognizerDelegate, ARSKViewDelegate, ARSessionDelegate {
@IBOutlet weak var sceneView: ARSKView!
// The view controller that displays the status and "restart experience" UI.
private lazy var statusViewController: StatusViewController = {
return children.lazy.compactMap({ $0 as? StatusViewController }).first!
}()
// MARK: - View controller lifecycle
override func viewDidLoad() {
super.viewDidLoad()
// Configure and present the SpriteKit scene that draws overlay content.
let overlayScene = SKScene()
overlayScene.scaleMode = .aspectFill
sceneView.delegate = self
sceneView.presentScene(overlayScene)
sceneView.session.delegate = self
// Hook up status view controller callback.
statusViewController.restartExperienceHandler = { [unowned self] in
self.restartSession()
}
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
// Create a session configuration
let configuration = ARWorldTrackingConfiguration()
// Run the view's session
sceneView.session.run(configuration)
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
// Pause the view's session
sceneView.session.pause()
}
// MARK: - ARSessionDelegate
// Pass camera frames received from ARKit to Vision (when not already processing one)
/// - Tag: ConsumeARFrames
func session(_ session: ARSession, didUpdate frame: ARFrame) {
// Do not enqueue other buffers for processing while another Vision task is still running.
// The camera stream has only a finite amount of buffers available; holding too many buffers for analysis would starve the camera.
guard currentBuffer == nil, case .normal = frame.camera.trackingState else {
return
}
// Retain the image buffer for Vision processing.
self.currentBuffer = frame.capturedImage
classifyCurrentImage()
}
// MARK: - Vision classification
// Vision classification request and model
/// - Tag: ClassificationRequest
private lazy var classificationRequest: VNCoreMLRequest = {
do {
// Instantiate the model from its generated Swift class.
let model = try VNCoreMLModel(for: Inceptionv3().model)
let request = VNCoreMLRequest(model: model, completionHandler: { [weak self] request, error in
self?.processClassifications(for: request, error: error)
})
// Crop input images to square area at center, matching the way the ML model was trained.
request.imageCropAndScaleOption = .centerCrop
// Use CPU for Vision processing to ensure that there are adequate GPU resources for rendering.
request.usesCPUOnly = true
return request
} catch {
fatalError("Failed to load Vision ML model: \(error)")
}
}()
// The pixel buffer being held for analysis; used to serialize Vision requests.
private var currentBuffer: CVPixelBuffer?
// Queue for dispatching vision classification requests
private let visionQueue = DispatchQueue(label: "com.example.apple-samplecode.ARKitVision.serialVisionQueue")
// Run the Vision+ML classifier on the current image buffer.
/// - Tag: ClassifyCurrentImage
private func classifyCurrentImage() {
// Most computer vision tasks are not rotation agnostic so it is important to pass in the orientation of the image with respect to device.
let orientation = CGImagePropertyOrientation(UIDevice.current.orientation)
let requestHandler = VNImageRequestHandler(cvPixelBuffer: currentBuffer!, orientation: orientation)
visionQueue.async {
do {
// Release the pixel buffer when done, allowing the next buffer to be processed.
defer { self.currentBuffer = nil }
try requestHandler.perform([self.classificationRequest])
} catch {
print("Error: Vision request failed with error \"\(error)\"")
}
}
}
// Classification results
private var identifierString = ""
private var confidence: VNConfidence = 0.0
// Handle completion of the Vision request and choose results to display.
/// - Tag: ProcessClassifications
func processClassifications(for request: VNRequest, error: Error?) {
guard let results = request.results else {
print("Unable to classify image.\n\(error!.localizedDescription)")
return
}
// The `results` will always be `VNClassificationObservation`s, as specified by the Core ML model in this project.
let classifications = results as! [VNClassificationObservation]
// Show a label for the highest-confidence result (but only above a minimum confidence threshold).
if let bestResult = classifications.first(where: { result in result.confidence > 0.5 }),
let label = bestResult.identifier.split(separator: ",").first {
identifierString = String(label)
confidence = bestResult.confidence
} else {
identifierString = ""
confidence = 0
}
DispatchQueue.main.async { [weak self] in
self?.displayClassifierResults()
}
}
// Show the classification results in the UI.
private func displayClassifierResults() {
guard !self.identifierString.isEmpty else {
return // No object was classified.
}
let message = String(format: "Detected \(self.identifierString) with %.2f", self.confidence * 100) + "% confidence"
statusViewController.showMessage(message)
}
// MARK: - Tap gesture handler & ARSKViewDelegate
// Labels for classified objects by ARAnchor UUID
private var anchorLabels = [UUID: String]()
// When the user taps, add an anchor associated with the current classification result.
/// - Tag: PlaceLabelAtLocation
@IBAction func placeLabelAtLocation(sender: UITapGestureRecognizer) {
let hitLocationInView = sender.location(in: sceneView)
let hitTestResults = sceneView.hitTest(hitLocationInView, types: [.featurePoint, .estimatedHorizontalPlane])
if let result = hitTestResults.first {
// Add a new anchor at the tap location.
let anchor = ARAnchor(transform: result.worldTransform)
sceneView.session.add(anchor: anchor)
// Track anchor ID to associate text with the anchor after ARKit creates a corresponding SKNode.
anchorLabels[anchor.identifier] = identifierString
}
}
// When an anchor is added, provide a SpriteKit node for it and set its text to the classification label.
/// - Tag: UpdateARContent
func view(_ view: ARSKView, didAdd node: SKNode, for anchor: ARAnchor) {
guard let labelText = anchorLabels[anchor.identifier] else {
fatalError("missing expected associated label for anchor")
}
let label = TemplateLabelNode(text: labelText)
node.addChild(label)
}
// MARK: - AR Session Handling
func session(_ session: ARSession, cameraDidChangeTrackingState camera: ARCamera) {
statusViewController.showTrackingQualityInfo(for: camera.trackingState, autoHide: true)
switch camera.trackingState {
case .notAvailable, .limited:
statusViewController.escalateFeedback(for: camera.trackingState, inSeconds: 3.0)
case .normal:
statusViewController.cancelScheduledMessage(for: .trackingStateEscalation)
// Unhide content after successful relocalization.
setOverlaysHidden(false)
}
}
func session(_ session: ARSession, didFailWithError error: Error) {
guard error is ARError else { return }
let errorWithInfo = error as NSError
let messages = [
errorWithInfo.localizedDescription,
errorWithInfo.localizedFailureReason,
errorWithInfo.localizedRecoverySuggestion
]
// Filter out optional error messages.
let errorMessage = messages.compactMap({ $0 }).joined(separator: "\n")
DispatchQueue.main.async {
self.displayErrorMessage(title: "The AR session failed.", message: errorMessage)
}
}
func sessionWasInterrupted(_ session: ARSession) {
setOverlaysHidden(true)
}
func sessionShouldAttemptRelocalization(_ session: ARSession) -> Bool {
/*
Allow the session to attempt to resume after an interruption.
This process may not succeed, so the app must be prepared
to reset the session if the relocalizing status continues
for a long time -- see `escalateFeedback` in `StatusViewController`.
*/
return true
}
private func setOverlaysHidden(_ shouldHide: Bool) {
sceneView.scene!.children.forEach { node in
if shouldHide {
// Hide overlay content immediately during relocalization.
node.alpha = 0
} else {
// Fade overlay content in after relocalization succeeds.
node.run(.fadeIn(withDuration: 0.5))
}
}
}
private func restartSession() {
statusViewController.cancelAllScheduledMessages()
statusViewController.showMessage("RESTARTING SESSION")
anchorLabels = [UUID: String]()
let configuration = ARWorldTrackingConfiguration()
sceneView.session.run(configuration, options: [.resetTracking, .removeExistingAnchors])
}
// MARK: - Error handling
private func displayErrorMessage(title: String, message: String) {
// Present an alert informing about the error that has occurred.
let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
let restartAction = UIAlertAction(title: "Restart Session", style: .default) { _ in
alertController.dismiss(animated: true, completion: nil)
self.restartSession()
}
alertController.addAction(restartAction)
present(alertController, animated: true, completion: nil)
}
}
最佳答案
这表明您的类StatusViewController不会从UIViewController继承，因为children的属性已在UIViewController的子类中使用了一段时间。
您是否可以分享您的StatusViewController组成方式？