<分区>
我正在尝试在缓存目录中保存带有叠加层的 map 快照，并在它存在时检索它。但是，尽管正在创建文件，但当我尝试检索它时 UIImage(contentsOfFile:) 返回 nil。我已经打印了写入和读取的文件路径，它们是相同的，并且通过下载容器并检查目录和文件确实存在来验证文件是否存在。
知道这里的问题是什么吗？
let cachesDirectory: URL = {
let urls = FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask)
return urls[urls.endIndex - 1]
}()
let mapCachesDirectory = cachesDirectory.appendingPathComponent("map-snapshots", isDirectory: true)
func configureMap(data: NSSet?) {
mapView.isZoomEnabled = false
mapView.isScrollEnabled = false
mapView.isUserInteractionEnabled = false
guard let data = data as? Set<SessionData>, data.count > 0 else { return }
activityIndicatorView.isHidden = false
activityIndicatorView.startAnimating()
DispatchQueue.global(qos: .userInitiated).async {
var points = [CLLocationCoordinate2D]()
for object in data {
guard object.locationLatitude != 0, object.locationLatitude != 0 else { continue }
points.append(CLLocationCoordinate2DMake(object.locationLatitude, object.locationLongitude))
}
DispatchQueue.main.async(execute: {
self.createOverlay(points: points)
self.activityIndicatorView.stopAnimating()
self.activityIndicatorView.isHidden = true
self.cacheMapImage(view: self.mapView)
})
}
}
func cacheMapImage(view: UIView) {
UIGraphicsBeginImageContextWithOptions(view.bounds.size, true, 0)
view.drawHierarchy(in: view.bounds, afterScreenUpdates: true)
let compositeImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
DispatchQueue.global(qos: .userInitiated).async {
if let compositeImage = compositeImage, let info = self.info {
let data = UIImagePNGRepresentation(compositeImage)
do {
var isDirectory: ObjCBool = false
let fileManager = FileManager.default
if fileManager.fileExists(atPath: self.mapCachesDirectory.absoluteString, isDirectory: &isDirectory) == false {
try fileManager.createDirectory(at: self.mapCachesDirectory, withIntermediateDirectories: true, attributes: nil)
}
let fileURL = self.mapCachesDirectory.appendingPathComponent(info.uid).appendingPathExtension("png")
try data?.write(to: fileURL)
print("\(fileURL.absoluteString) Saved")
} catch {
log.error(error)
}
}
}
}
func cachedMapImage() -> UIImage? {
guard let info = info else { return nil }
let filePath = mapCachesDirectory.appendingPathComponent(info.uid).appendingPathExtension("png").absoluteString
let image = UIImage(contentsOfFile: filePath)
print("\(filePath): \(image)")
return image
}
func createOverlay(points: [CLLocationCoordinate2D]) {
guard points.count > 0 else { return }
let overlay = MKGeodesicPolyline(coordinates: points, count: points.count)
mapView.add(overlay)
let inset: CGFloat = 50.0
mapView.setVisibleMapRect(overlay.boundingMapRect, edgePadding: UIEdgeInsetsMake(inset,inset,inset,inset), animated: true)
}