我有一个将[CLLocation]
作为输入的函数。在while
循环内,它将其分成多个块,每个块发出一个MKDirection
请求,将响应存储在新的[CLLocation]
中,并在完成后返回。
问题在于新数组中的所有块都不是连续的,因此生成的路由会在整个位置上跳跃。我该如何等待上一个请求获得响应,然后再做出新请求?我尝试了DispatchQueue.global().sync
和DispatchQueue.main.sync
,但没有任何区别。
我尝试从Cannot wait for the result of MKDirections.calculate, getting nil instead of it实施第一个答案,这似乎是我的同样问题,但我不了解如何使其适应我的情况。
您能帮我按顺序获得答复吗?
这是函数,注释掉的部分用于路由的最新点,这将是最后一个请求。
一如既往,非常感谢您的帮助和时间。
func repositionLocation2(route: [CLLocation], completion: @escaping ([CLLocation]) -> Void) {
let group = DispatchGroup()
var pos = 0
var nextPos = 3
var repositioned = [CLLocation]()
// repositioned.append(route.first!)
guard route.count > nextPos else {print("Reposision Location failed, not enough positions");return}
let request = MKDirections.Request()
request.requestsAlternateRoutes = false
request.transportType = .walking
while pos < route.count - nextPos {
print(" pos in \(pos)")
// repositioned.removeAll()
group.enter()
// get a small chunk of the input route
let a = route[pos].coordinate//repositioned.last!.coordinate//
let b = route[pos + nextPos].coordinate
// get directions for the small chunk
request.source = MKMapItem(placemark: MKPlacemark(coordinate: a))
request.destination = MKMapItem(placemark: MKPlacemark(coordinate: b))
let directions = MKDirections(request: request)
// DispatchQueue.main.sync {
// DispatchQueue.global().sync {
// group.enter()
directions.calculate { [unowned self] response, error in
if let err = error {
print("direction error : \(err)")
}
guard let unwrappedResponse = response else {print("no suggested routes available"); return }
print("Response is: \(unwrappedResponse.debugDescription)")
guard let coord = unwrappedResponse.routes.first?.steps else {print("No coordinates");return}
print("coord is: \(coord)")
// save response coordinates into a new array
for location in coord {
let point: CLLocation = CLLocation(latitude: location.polyline.coordinate.latitude, longitude: location.polyline.coordinate.longitude)
print("point is: \(point)") // prints a correct CLLocation with coordinates
repositioned.append(point)
print("repositioned in for loop is : \(repositioned)") // prints just first appended location CLLocation with coordinates
// group.leave()
}
// group.wait() // hangs the app
completion(repositioned)
}
// }
print("repositioned in while loop is : \(repositioned)")
// shift to nex addiacent chunk
pos += 3
nextPos += 3
}
// // last chunk
// let a = route[pos - 5].coordinate//repositioned.last!.coordinate
// let b = route.last?.coordinate
// request.source = MKMapItem(placemark: MKPlacemark(coordinate: a))
// request.destination = MKMapItem(placemark: MKPlacemark(coordinate: b!))
// let directions = MKDirections(request: request)
// directions.calculate { [unowned self] response, error in
// if let err = error {
// print("direction error : \(err)")
// }
// guard let unwrappedResponse = response else {print("no suggested routes available"); return }
// print("Response is: \(unwrappedResponse.debugDescription)")
// guard let coord = unwrappedResponse.routes.first?.steps else {print("No coordinates");return}
// print("coord is: \(coord)")
// for location in coord {
//
// let point: CLLocation = CLLocation(latitude: location.polyline.coordinate.latitude, longitude: location.polyline.coordinate.longitude)
// print("point is: \(point)")
// repositioned.append(point)
// print("repositioned in for loop is : \(repositioned)")
// }
// completion(repositioned)
// }
// print("repositioned in while loop is : \(repositioned)")
}
答案 0 :(得分:1)
当您有一系列异步任务(可以按任意顺序完成)需要按顺序排列结果时,只需将其保存到与顺序无关紧要的结构中,最后对其进行排序即可。例如,您可以使用由整数索引索引的字典:
var routes: [Int: [CLLocationCoordinate2D]] = [:]
然后,当任何给定的循环结束时,就可以更新此字典:
routes[i] = ...
如果要在末尾进行排序的平面数组
let coordinates = steps.sorted { $0.0 < $1.0 }
.flatMap { $0.1 }
或者,您可以使用预先填充的可选数组,您可以在其中将特定路线插入数组中的正确位置:
var routes: [[CLLocationCoordinate2D]?] = Array(repeating: nil, count: pointCount - 1)
当您要更新一个时:
routes[i-1] = ...
然后,最后,您可以使用compactMap
删除可选内容,并使用flatMap
对其进行展平:
let coordinates = steps.compactMap { $0 }.flatMap { $0 }
因此:
func fetchDirections(_ locations: [CLLocation], completion: @escaping ([CLLocationCoordinate2D]) -> Void) {
let pointCount = locations.count
guard pointCount > 1 else { return }
var routes: [[CLLocationCoordinate2D]?] = Array(repeating: nil, count: pointCount - 1)
let group = DispatchGroup()
for i in 1 ..< pointCount {
group.enter()
directions(from: locations[i-1], to: locations[i]).calculate { response, error in
defer { group.leave() }
guard
error == nil,
let response = response,
let route = response.routes.first
else { return }
routes[i-1] = self.coordinates(for: route.steps)
}
}
group.notify(queue: .main) {
let coordinates = routes.compactMap { $0 }.flatMap { $0 }
completion(coordinates)
}
}
func directions(from: CLLocation, to: CLLocation) -> MKDirections {
let request = MKDirections.Request()
request.source = MKMapItem(placemark: MKPlacemark(coordinate: from.coordinate))
request.destination = MKMapItem(placemark: MKPlacemark(coordinate: to.coordinate))
request.requestsAlternateRoutes = false
request.transportType = .walking
return MKDirections(request: request)
}
func coordinates(for steps: [MKRoute.Step]) -> [CLLocationCoordinate2D] {
guard !steps.isEmpty else { return [] }
var coordinates: [CLLocationCoordinate2D] = []
for step in steps {
let count = step.polyline.pointCount
let pointer = step.polyline.points()
for i in 0 ..< count {
let coordinate = pointer[i].coordinate
if coordinate.latitude != coordinates.last?.latitude, coordinate.longitude != coordinates.last?.longitude {
coordinates.append(coordinate)
}
}
}
return coordinates
}
位置:
fetchDirections(locations) { coordinates in
let polyline = MKPolyline(coordinates: coordinates, count: coordinates.count)
self.mapView.addOverlay(polyline)
}
屈服,在Apple大楼内漫步:
顺便说一句,请注意,我不仅在使用coordinate
的{{1}}中的polyline
。那是折线的中心。您大概想遍历points()
。
话虽这么说,当我获得路线指示时,通常只是将其显示在地图上,所以我通常只是直接将MKRoute.Step
添加为叠加层,而不必理会将其分解为polyline
,但我认为您还有其他理由要这样做。