我的应用程序使用Geojson文件.我使用
MapBox SDK将MGLpolyline添加到地图中.但问题是我的文件太大,以至于应用程序崩溃并收到错误：来自调试器的消息：由于内存问题而终止.我在第一次循环时面对66234个对象.我试图将数组块化为新数组,但没有成功.请帮我解决问题.这是我在地图上绘制的代码,这里是我的
test project on github use Xcode 8.1如果有任何不同的第三方可以解决我的问题也欢迎：
func drawpolyline() { // Parsing GeoJSON can be cpu intensive,do it on a background thread dispatchQueue.global(qos: .background).async { // Get the path for example.geojson in the app's bundle let jsonPath = Bundle.main.path(forResource: "KMLMAPNew",ofType: "json") let jsonData = NSData(contentsOfFile: jsonPath!) do { // Load and serialize the GeoJSON into a dictionary filled with properly-typed objects guard let jsonDict = try JSONSerialization.jsonObject(with: jsonData! as Data,options: []) as? Dictionary<String,AnyObject>,let features = jsonDict["features"] as? Array<AnyObject> else{return} for feature in features { guard let feature = feature as? Dictionary<String,let geometry = feature["geometry"] as? Dictionary<String,AnyObject> else{ continue } if geometry["type"] as? String == "Linestring" { // Create an array to hold the formatted coordinates for our line var coordinates: [CLLocationCoordinate2D] = [] if let locations = geometry["coordinates"] as? Array<AnyObject> { // Iterate over line coordinates,stored in GeoJSON as many lng,lat arrays for location in locations { // Make a CLLocationCoordinate2D with the lat,lng if let location = location as? Array<AnyObject>{ let coordinate = CLLocationCoordinate2DMake(location[1].doubleValue,location[0].doubleValue) // Add coordinate to coordinates array coordinates.append(coordinate) } } } let line = MGLpolyline(coordinates: &coordinates,count: UInt(coordinates.count)) // Optionally set the title of the polyline,which can be used for: // - Callout view // - Object identification line.title = "Crema to Council Crest" // Add the annotation on the main thread dispatchQueue.main.async { // UNowned reference to self to prevent retain cycle [uNowned self] in self.mapBoxView.addAnnotation(line) } } } } catch { print("GeoJSON parsing Failed") } } }
编辑:: @ Alessandro Ornano和@fragilecat非常感谢.但这些解决方案仍然无法解决iPad终止应用的问题.我认为很难改变当前的代码以使其正常工作,因为数据太大了.我想我需要另一种适用于大数据的解决方案.就像将数组分块到小数组中一样,然后通过队列加载它们.但我不知道如何开始:(
解决方法
这里的问题与有效的内存管理有关.您正在通过json文件加载大量数据.您意识到您需要在后台队列(线程)上完成大部分工作,但问题是如何通过dispatchQueue.main.async函数更新UI.在当前版本的drawpolyline()方法中,在给定第一个循环中的对象数量的情况下,您将在后台队列和主队列之间切换66234次.您还创建了相同数量的CLLocationCoordinate2D数组.
这导致巨大的内存占用.您没有提到有关如何渲染线条的任何要求.因此,如果我们重新构建drawpolyline()方法以使用CLLocationCoordinate2D数组的实例变量,那么我们只使用一个,然后在更新UI之前处理所有json文件.内存使用量下降到更可管理的664.6 MB.
当然,渲染可能并不完全符合您的要求,如果是这种情况,您可能希望将CLLocationCoordinate2D数组重组为更合适的数据结构.
下面是您的ViewController类,其中重写的drawpolyline()为drawpolyline2()
import UIKit import MapBox class ViewController: UIViewController,MGLMapViewDelegate { @IBOutlet var mapBoxView: MGLMapView! fileprivate var coordinates = [[CLLocationCoordinate2D]]() fileprivate var jsonData: NSData? override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view,typically from a nib. mapBoxView = MGLMapView(frame: view.bounds) mapBoxView.autoresizingMask = [.flexibleWidth,.flexibleHeight] // mapBoxView.setCenter(CLLocationCoordinate2D(latitude: 45.5076,longitude: -122.6736),// zoomLevel: 11,animated: false) mapBoxView.setCenter(CLLocationCoordinate2D(latitude: 1.290270,longitude: 103.851959),zoomLevel: 11,animated: false) view.addSubview(self.mapBoxView) mapBoxView.delegate = self mapBoxView.allowsZooming = true drawpolyline2() //newWay() } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // dispose of any resources that can be recreated. } func drawpolyline2() { dispatchQueue.global(qos: .background).async { if let path = Bundle.main.path(forResource: "KMLMAPNew",ofType: "json") { let fileURL = URL(fileURLWithPath: path) if let data = try? Data(contentsOf: fileURL) { do { let dictionary = try JSONSerialization.jsonObject(with: data as Data,AnyObject> if let features = dictionary?["features"] as? Array<AnyObject> { print("** START **") for feature in features { guard let feature = feature as? Dictionary<String,AnyObject> else { continue } if geometry["type"] as? String == "Linestring" { // Create an array to hold the formatted coordinates for our line if let locations = geometry["coordinates"] as? Array<AnyObject> { // Iterate over line coordinates,lat arrays var featureCoordinates = [CLLocationCoordinate2D]() for location in locations { // Make a CLLocationCoordinate2D with the lat,lng if let location = location as? Array<AnyObject>{ let coordinate = CLLocationCoordinate2DMake(location[1].doubleValue,location[0].doubleValue) // Add coordinate to coordinates array featureCoordinates.append(coordinate) } } // Uncomment if you need to store for later use. //self.coordinates.append(featureCoordinates) dispatchQueue.main.async { let line = MGLpolyline(coordinates: &featureCoordinates,count: UInt(featureCoordinates.count)) // Optionally set the title of the polyline,which can be used for: // - Callout view // - Object identification line.title = "Crema to Council Crest" self.mapBoxView.addAnnotation(line) } } } } print("** FINISH **") } } catch { print("GeoJSON parsing Failed") } } } } } func drawSmallListObj(list: [Dictionary<String,AnyObject>]){ for obj in list{ // print(obj) if let feature = obj as? Dictionary<String,AnyObject> { if let geometry = feature["geometry"] as? Dictionary<String,AnyObject> { if geometry["type"] as? String == "Linestring" { // Create an array to hold the formatted coordinates for our line var coordinates: [CLLocationCoordinate2D] = [] if let locations = geometry["coordinates"] as? Array<AnyObject> { // Iterate over line coordinates,which can be used for: // - Callout view // - Object identification line.title = "Crema to Council Crest" // Add the annotation on the main thread dispatchQueue.main.async { // UNowned reference to self to prevent retain cycle [uNowned self] in self.mapBoxView.addAnnotation(line) } } } } } } func mapView(_ mapView: MGLMapView,alphaForShapeAnnotation annotation: MGLShape) -> CGFloat { // Set the alpha for all shape annotations to 1 (full opacity) return 1 } func mapView(_ mapView: MGLMapView,linewidthForpolylineAnnotation annotation: MGLpolyline) -> CGFloat { // Set the line width for polyline annotations return 2.0 } func mapView(_ mapView: MGLMapView,strokeColorForShapeAnnotation annotation: MGLShape) -> UIColor { // Give our polyline a unique color by checking for its `title` property if (annotation.title == "Crema to Council Crest" && annotation is MGLpolyline) { // MapBox cyan return UIColor(red: 59/255,green:178/255,blue:208/255,alpha:1) } else { return UIColor.red } } }
