状态恢复MKMapView稍微缩小

Question

为mapView恢复状态时，它会在保存期间略微缩小。我创建了一个iOS单视图应用程序，其中只包含一个填充整个视图的MKMapView来尝试对此进行故障排除。我的调试打印语句显示正在保存和恢复地图值，但跨度纬度或经度最终会发生变化。我错过了什么？

编辑：

这个问题与以下主题相同： MKMapView setRegion "snaps" to predefined zoom levels? MKMapView show incorrectly saved region

作为实验，我添加了一个MKCoordinateRegion类型的类变量，并将decodeRestorableState方法中读取的区域分配给它。我还为视图控制器添加了一个按钮和动作处理程序，它将mapView的区域设置为添加的变量的值。点击按钮时，地图会缩放到恢复期望的位置。我很奇怪，位置坐标在decodeRestorableState方法中工作不正确，但这些相同的坐标在按钮的动作处理程序中正常工作。

import UIKit
import MapKit

class ViewController: UIViewController {
    @IBOutlet weak var mapView: MKMapView!
}

extension MKMapView {
    override open func encodeRestorableState(with coder: NSCoder) {
        super.encodeRestorableState(with: coder)
        region.encodeRestorableState(with: coder)
        camera.encodeRestorableState(with: coder)
    }

    override open func decodeRestorableState(with coder: NSCoder) {
        super.decodeRestorableState(with: coder)
        region.decodeRestorableState(with: coder)
        camera.decodeRestorableState(with: coder)
    }
}

extension MKCoordinateRegion {
    private static let KEY_LATITUDE  = "Region.latitude"
    private static let KEY_LONGITUDE = "Region.longitude"
    private static let KEY_WIDTH     = "Region.spanWidth"
    private static let KEY_HEIGHT    = "Region.spanHeight"

    func encodeRestorableState(with coder: NSCoder) {
        coder.encode(center.latitude, forKey: MKCoordinateRegion.KEY_LATITUDE)
        coder.encode(center.longitude, forKey: MKCoordinateRegion.KEY_LONGITUDE)
        coder.encode(span.latitudeDelta, forKey: MKCoordinateRegion.KEY_HEIGHT)
        coder.encode(span.longitudeDelta, forKey: MKCoordinateRegion.KEY_WIDTH)
    }

    mutating func decodeRestorableState(with coder: NSCoder) {
        center.latitude = coder.decodeDouble(forKey: MKCoordinateRegion.KEY_LATITUDE)
        center.longitude = coder.decodeDouble(forKey: MKCoordinateRegion.KEY_LONGITUDE)
        span.latitudeDelta = coder.decodeDouble(forKey: MKCoordinateRegion.KEY_HEIGHT)
        span.longitudeDelta = coder.decodeDouble(forKey: MKCoordinateRegion.KEY_WIDTH)
    }
}

extension MKMapCamera {
    private static let KEY_ALTITUDE  = "Camera.altitude"
    private static let KEY_HEADING   = "Camera.heading"
    private static let KEY_PITCH     = "Camera.pitch"
    private static let KEY_LATITUDE  = "Camera.latitude"
    private static let KEY_LONGITUDE = "Camera.longitude"

    func encodeRestorableState(with coder: NSCoder) {
        coder.encode(altitude, forKey: MKMapCamera.KEY_ALTITUDE)
        coder.encode(heading, forKey: MKMapCamera.KEY_HEADING)
        coder.encode(Double(pitch), forKey: MKMapCamera.KEY_PITCH)
        coder.encode(centerCoordinate.latitude, forKey: MKMapCamera.KEY_LATITUDE)
        coder.encode(centerCoordinate.longitude, forKey: MKMapCamera.KEY_LONGITUDE)
    }

    func decodeRestorableState(with coder: NSCoder) {
        altitude = coder.decodeDouble(forKey: MKMapCamera.KEY_ALTITUDE)
        heading = coder.decodeDouble(forKey: MKMapCamera.KEY_HEADING)
        pitch = CGFloat(coder.decodeDouble(forKey: MKMapCamera.KEY_PITCH))
        centerCoordinate.latitude = coder.decodeDouble(forKey: MKMapCamera.KEY_LATITUDE)
        centerCoordinate.longitude = coder.decodeDouble(forKey: MKMapCamera.KEY_LONGITUDE)
    }
}

Answer 1

有同样的问题。我的解决方法是在视图控制器的viewDidAppear中设置mapView.camera。

let mapCameraKey = "MapCameraKey"
var restoredCamera: MKMapCamera?

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    if let restoredCamera = restoredCamera {
        mapView.camera = restoredCamera
    }
}

override func encodeRestorableState(with coder: NSCoder) {
    super.encodeRestorableState(with: coder)

    coder.encode(mapView.camera, forKey: mapCameraKey)
}

override func decodeRestorableState(with coder: NSCoder) {
    super.decodeRestorableState(with: coder)

    restoredCamera = coder.decodeObject(forKey: mapCameraKey) as? MKMapCamera
}