ios - 在 Swift 中将图像发送到 ViewController 的多个实例

Question

我在程序中从 CloudKit 下载了几个“事件”。每一张都包含图片、标题和位置。后两个立即使用，没有问题。仅当用户单击注释上的信息按钮(使用单独的 View Controller 显示图片)时才能看到该图像。我在使用 ViewController 之前无法将图像传递到 ViewController，同时又保持每个事件的图片独立。

这里是从 CloudKit 查询每条记录并将其放入 for 循环中，然后发送到下面的方法:

func loadEvent(_ completion: @escaping (_ error:NSError?, _ records:[CKRecord]?) -> Void)
    {
        //...record is downloaded from cloudkit

                for record in records
                {
                    if let asset = record["Picture"] as? CKAsset,
                        let data = NSData(contentsOf: asset.fileURL),
                        let image1 = UIImage(data: data as Data)
                    {
                        self.drawEvents(record["LocationF"] as! CLLocation, title1: record["StringF"] as! String, pic1: image1)
                    }
                }
            }

这里是分配变量并用于创建点注释的位置(它是包含图像的自定义注释):

func drawEvents(_ loc: CLLocation, title1: String, pic1: UIImage)
    {
        mapView.delegate = self
        let center = CLLocationCoordinate2D(latitude: loc.coordinate.latitude, longitude: loc.coordinate.longitude)
        let lat: CLLocationDegrees = center.latitude
        let long: CLLocationDegrees = center.longitude
        self.pointAnnotation1 = CustomPointAnnotation()
        self.pointAnnotation1.imageName = pic1
        self.pointAnnotation1.title = title1
        self.pointAnnotation1.subtitle = "Event"
        self.pointAnnotation1.coordinate = CLLocationCoordinate2D(latitude: lat, longitude: long)
        self.pinAnnotationView = MKPinAnnotationView(annotation: self.pointAnnotation1, reuseIdentifier: nil)
        self.mapView.addAnnotation(self.pinAnnotationView.annotation!)
    }

下面是当单击 MKMapAnnotation 上的信息按钮时使 EventPage 显示的函数:

    func mapView(_ mapView: MKMapView, annotationView view: MKAnnotationView, calloutAccessoryControlTapped control: UIControl) {

            let eventPageViewController:EventPageViewController = storyboard?.instantiateViewController(withIdentifier: "EventPage") as! EventPageViewController

            self.present(eventPageViewController, animated: true, completion: nil)
        }

这是 EventPage 的 ViewController:

class EventPageViewController: UIViewController {

    @IBOutlet weak var eventPic: UIImageView!

    var photo: UIImage!

    override func viewDidLoad() {
        super.viewDidLoad()

        let firstViewController:FirstViewController = storyboard?.instantiateViewController(withIdentifier: "Home") as! FirstViewController

        photo = firstViewController.pointAnnotation1.imageName 
        //photo is nil

        eventPic.image = photo
   }
}

Answer 1

不要将注释存储在单个实例属性中(这意味着您只能访问最后一个注释)，而是将它们存储在数组中，尽管您根本不需要存储它们来响应点击.

var annotations = [CustomPointAnnotation]()

func drawEvents(_ loc: CLLocation, title1: String, pic1: UIImage)
{
    mapView.delegate = self
    let center = CLLocationCoordinate2D(latitude: loc.coordinate.latitude, longitude: loc.coordinate.longitude)
    let lat: CLLocationDegrees = center.latitude
    let long: CLLocationDegrees = center.longitude
    var newAnnotation = CustomPointAnnotation()
    newAnnotation = CustomPointAnnotation()
    newAnnotation.imageName = pic1
    newAnnotation.title = title1
    newAnnotation.subtitle = "Event"
    newAnnotation.coordinate = CLLocationCoordinate2D(latitude: lat, longitude: long)
    self.mapView.addAnnotation(newAnnotation)
    self.annotations.append(newAnnotation)
}

点击的注释 View 将传递给您的委托(delegate)方法，因此您知道它是哪个项目。注释 View 的注释属性是您的 CustomPointAnnotation 实例。

func mapView(_ mapView: MKMapView, annotationView view: MKAnnotationView, calloutAccessoryControlTapped control: UIControl) {

    let eventPageViewController:EventPageViewController = storyboard?.instantiateViewController(withIdentifier: "EventPage") as! EventPageViewController

    if let annotation = view.annotation as CustomPointAnnotation {
        eventPageViewController.photo = annotation.imageName
    }

    self.present(eventPageViewController, animated: true, completion: nil)
}