问题
I'm working with ARKit, I have trouble getting download progress from SCNScene url. This is my code:
func downloadModel(hitTestResult: ARHitTestResult) {
DispatchQueue.global().async {
// create loading view
// I WANT TO GET DOWNLOAD PROGRESS HERE
let loading = UIAlertController(title: nil, message: "Please wait...\(downloadProgressValueHere)%", preferredStyle: .alert)
let loadingIndicator = UIActivityIndicatorView(frame: CGRect(x: 10, y: 5, width: 50, height: 50))
loadingIndicator.hidesWhenStopped = true
loadingIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.gray
loadingIndicator.startAnimating();
loading.view.addSubview(loadingIndicator)
self.present(loading, animated: true, completion: nil)
// download 3d model from server
let myURL = URL(string: "http://www.mydownloadlink.com")
let scene = try! SCNScene(url: myURL!, options: nil)
let node = (scene.rootNode.childNode(withName: "parentNode", recursively: true))!
self.sceneView.scene.rootNode.addChildNode(node)
// dismiss loading view
loading.dismiss(animated: true, completion: nil)
}
}
How can I get download progress to "Please wait..." message? Thanks all.
回答1:
It is my understanding that whilst it appears that the following method would take a remote URL in actuality it doesn't (although I could be wrong):
convenience init(url: URL,
options: [SCNSceneSource.LoadingOption : Any]? = nil) throws
Anyway to answer your question here is an example for you (which is probably a bit OTT, but hopefully it will help others as well).
Lets say we an SCNScene file at the following URL:
http://stackOverflow.com/stackOverFlow.scn
Firstly we need to create variables for our ProgressInfo like so:
var loading: UIAlertController!
var loadingIndicator: UIActivityIndicatorView!
var downloadString: String = "Downloading"
Then what we will do is create a URLSession to download the file like so:
/// Downloads An SCNFile From A Remote URL
func downloadSceneTask(){
//1. Get The URL Of The SCN File
guard let url = URL(string: "http://stackOverflow.com/stackOverFlow.scn") else { return }
//2. Create The Download Session
let downloadSession = URLSession(configuration: URLSession.shared.configuration, delegate: self, delegateQueue: nil)
//3. Create The Download Task & Run It
let downloadTask = downloadSession.downloadTask(with: url)
downloadTask.resume()
//4. Show The Progress Alert
DispatchQueue.main.async {
self.loading = UIAlertController(title: nil, message: self.downloadString , preferredStyle: .alert)
let loadingIndicator = UIActivityIndicatorView(frame: CGRect(x: 10, y: 5, width: 50, height: 50))
loadingIndicator.hidesWhenStopped = true
loadingIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.gray
loadingIndicator.startAnimating();
self.loading.view.addSubview(loadingIndicator)
self.present(self.loading, animated: true, completion: nil)
}
}
Note that I have create a variable caused downloadString which we change later.
We will then make reference to following URLSession Delegates e.g:
class ViewController: UIViewController, URLSessionDelegate, URLSessionDownloadDelegate {
}
Which for our example will call the following functions:
The 1st to track the progress of our download in which you can handle things like showing the progress in a HUD or using a progressIndicator:
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask,
didWriteData bytesWritten: Int64,
totalBytesWritten: Int64,
totalBytesExpectedToWrite: Int64) {
print("Downloaded \(totalBytesWritten) / Of \(totalBytesExpectedToWrite) Bytes")
DispatchQueue.main.async {
self.loading.message = "Downloaded \(totalBytesWritten) / Of \(totalBytesExpectedToWrite) Bytes"
}
}
The 2nd to handle when the file has downloaded:
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
//1. Remove The Loading View
loading.dismiss(animated: true, completion: nil)
//2. Create The Filename
let fileURL = getDocumentsDirectory().appendingPathComponent("stackOverFlow.scn")
//3. Copy It To The Documents Directory
do {
try FileManager.default.copyItem(at: location, to: fileURL)
print("Successfuly Saved File \(fileURL)")
//4. Load The Model
loadModel()
} catch {
print("Error Saving: \(error)")
}
}
Note that in this method I am making use of the following function to retrieve and copy the downloaded file to the documents directory:
/// Returns The Documents Directory
///
/// - Returns: URL
func getDocumentsDirectory() -> URL {
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let documentsDirectory = paths[0]
return documentsDirectory
}
Once the file has been downloaded and copied across we then (4) call our loadModel function like so:
/// Loads The SCNFile From The Documents Directory
func loadModel(){
//1. Get The Path Of The Downloaded File
let downloadedScenePath = getDocumentsDirectory().appendingPathComponent("stackOverFlow.scn")
do {
//2. Load The Scene Remembering The Init Takes ONLY A Local URL
let modelScene = try SCNScene(url: downloadedScenePath, options: nil)
//3. Create A Node To Hold All The Content
let modelHolderNode = SCNNode()
//4. Get All The Nodes From The SCNFile
let nodeArray = modelScene.rootNode.childNodes
//5. Add Them To The Holder Node
for childNode in nodeArray {
modelHolderNode.addChildNode(childNode as SCNNode)
}
//6. Set The Position
modelHolderNode.position = SCNVector3(0, 0, -1.5)
//7. Add It To The Scene
self.augmentedRealityView?.scene.rootNode.addChildNode(modelHolderNode)
} catch {
print("Error Loading Scene")
}
}
Please note that this is a very crude example, and doesn't cover things like checking if the file exists, scaling etc, but it should be enough to help you achieve what you are looking for...
来源：https://stackoverflow.com/questions/50018196/get-download-progress-from-scnscene-url