ios - CollectionView 单元格内的 MapView 不显示折线 Swift 4

Question

我有一个 CollectionView，它显示保存到 CoreData 中的所有跟踪路线。除了单元格内 map 上缺少多段线之外，一切正常。我认为这是因为我忘记导入 CoreLocation 并将其委托(delegate)分配给 ViewCOntroller，但添加后它仍然没有显示。在cell配置中，我从获取的对象中打印数组，并且它打印正确。在我的主MapViewController中，我使用相同的过程，但这里没有按预期工作。你能看到我错过了什么吗？这是 ViewController` 的代码:

import UIKit
import MapKit
import CoreData
import CoreLocation

class MyRoutesViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, MKMapViewDelegate, CLLocationManagerDelegate {

    @IBOutlet weak var routeCollectionView: UICollectionView!

    @IBOutlet weak var myRoutesButton: UIButton!

    var fetchedResultController: NSFetchedResultsController<Route>!


    override func viewDidLoad() {
        super.viewDidLoad()

        routeCollectionView.dataSource = self
        routeCollectionView.delegate = self

        myRoutesButton.layer.borderWidth = 1
        myRoutesButton.layer.masksToBounds = true
        myRoutesButton.layer.cornerRadius = myRoutesButton.frame.height/4
        myRoutesButton.layer.borderColor = UIColor.white.cgColor
        configureFetchedResultsController()
    }

    func configureFetchedResultsController() {
        let context = AppDelegate.viewContext
        let fetchRequest = NSFetchRequest<Route>(entityName: "Route")
        fetchRequest.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
        fetchedResultController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
        do {
            try fetchedResultController.performFetch()
            print("fetched")
        } catch  {
            fatalError("failed to fetch entities: \(error)")
        }
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        guard let sections = self.fetchedResultController?.sections else {
            fatalError("no sections in fetchedResultController" )
        }
        let sectionInfo = sections[section]
        return sectionInfo.numberOfObjects
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Route Cell", for: indexPath as IndexPath) as! RouteCell
        let route = self.fetchedResultController?.object(at: indexPath)

        cell.titleValueLabel.text = route!.name //RoutesArray.routeArray[indexPath.row].routeName ?? ""
        cell.distanceValueLabel.text = route!.distance //RoutesArray.routeArray[indexPath.row].distance ?? ""
        cell.durationValueLabel.text = route!.duration //RoutesArray.routeArray[indexPath.row].duration ?? ""

        do {
            let decodedCoordinates = try JSONDecoder().decode([CLLocationCoordinate2D].self, from: route!.coordinates!)
            print("decodedCoordinates are: \(decodedCoordinates)")
            let geodesic = MKGeodesicPolyline(coordinates: decodedCoordinates, count: decodedCoordinates.count)
            cell.map.add(geodesic)
            cell.map.setRegion(MKCoordinateRegionForMapRect(geodesic.boundingMapRect), animated: true)
        } catch {
            print(error)
        }
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, shouldShowMenuForItemAt indexPath: IndexPath) -> Bool {
        return true
    }


    @IBAction func MyRoutesButton(_ sender: UIButton) {

        performSegue(withIdentifier: "newRouteSegue", sender: self)
    }


    // RENDER OVERLAYS
    func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
        if overlay is MKCircle {
            let renderer = MKCircleRenderer(overlay: overlay)
            renderer.fillColor = UIColor.black.withAlphaComponent(0.1)
            renderer.strokeColor = UIColor.blue
            renderer.lineWidth = 2
            return renderer
        } else if overlay is MKPolyline {
            let renderer = MKPolylineRenderer(overlay: overlay)
            renderer.strokeColor = UIColor.orange
            renderer.lineWidth = 3
            return renderer
        } else if overlay is MKPolygon {
            let renderer = MKPolygonRenderer(polygon: overlay as! MKPolygon)
            renderer.fillColor = UIColor.black.withAlphaComponent(0.5)
            renderer.strokeColor = UIColor.orange
            renderer.lineWidth = 2
            return renderer
        }
        return MKOverlayRenderer()
    }
}

对于cell自定义类:

import UIKit
import MapKit
import CoreLocation

class RouteCell: UICollectionViewCell, MKMapViewDelegate {

    @IBOutlet weak var map: MKMapView!
    @IBOutlet weak var titleLabel: UILabel!
    @IBOutlet weak var titleValueLabel: UILabel!
    @IBOutlet weak var distanceLabel: UILabel!
    @IBOutlet weak var distanceValueLabel: UILabel!
    @IBOutlet weak var durationLabel: UILabel!
    @IBOutlet weak var durationValueLabel: UILabel!

 }

Answer 1

感谢@vadian 为我指明了正确的方向。我在定义 cell 属性时缺少将 cell 声明为 mapView delegate 。所以我刚刚在 cellForItemAt 函数中添加了 cell.map.delegate = self ，现在它可以正常工作了。再次感谢。