iOS 10 heading arrow for MKUserLocation dot

问题

The Maps app in iOS 10 now includes a heading direction arrow on top of the MKUserLocation MKAnnotationView. Is there some way I can add this to MKMapView in my own apps?

Edit: I'd be happy to do this manually, but I'm not sure if it's possible? Can I add an annotation to the map and have it follow the user's location, including animated moves?

回答1:

I also experienced this same issue (needing an orientation indicator without having the map spin around, similar to the Apple Maps app). Unfortunately Apple has not yet made the 'blue icon for heading' API available.

I created the following solution derived from @alku83's implementation.

Ensure the class conforms to MKViewDelegate

Add the delegate method to add a blue arrow icon to the maps location dot

func mapView(_ mapView: MKMapView, didAdd views: [MKAnnotationView]) {
    if views.last?.annotation is MKUserLocation {
        addHeadingView(toAnnotationView: views.last!)
    }
}

Add the method to create the 'blue arrow icon'.

func addHeadingView(toAnnotationView annotationView: MKAnnotationView) {
    if headingImageView == nil {
        let image = #YOUR BLUE ARROW ICON#
        headingImageView = UIImageView(image: image)
        headingImageView!.frame = CGRect(x: (annotationView.frame.size.width - image.size.width)/2, y: (annotationView.frame.size.height - image.size.height)/2, width: image.size.width, height: image.size.height)
        annotationView.insertSubview(headingImageView!, at: 0)
        headingImageView!.isHidden = true
     }
}

Add var headingImageView: UIImageView? to your class. This is mainly needed to transform/rotate the blue arrow image.

(In a different class/object depending on your architecture) Create a location manager instance, with the class conforming to CLLocationManagerDelegate protocol

lazy var locationManager: CLLocationManager = {
    let manager = CLLocationManager()
    // Set up your manager properties here
    manager.delegate = self
    return manager
}()

Ensure your location manager is tracking user heading data locationManager.startUpdatingHeading() and that it stops tracking when appropriate locationManager.stopUpdatingHeading()
Add var userHeading: CLLocationDirection? which will hold the orientation value

Add the delegate method to be notified of when the heading values change, and change the userHeading value appropriately

func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
     if newHeading.headingAccuracy < 0 { return }

     let heading = newHeading.trueHeading > 0 ? newHeading.trueHeading : newHeading.magneticHeading
     userHeading = heading
     NotificationCenter.default.post(name: Notification.Name(rawValue: #YOUR KEY#), object: self, userInfo: nil)
    }

Now in your class conforming to MKMapViewDelegate, add the method to 'transform' the orientation of the heading image

   func updateHeadingRotation() {
        if let heading = # YOUR locationManager instance#,
            let headingImageView = headingImageView {

            headingImageView.isHidden = false
            let rotation = CGFloat(heading/180 * Double.pi)
            headingImageView.transform = CGAffineTransform(rotationAngle: rotation)
        }
    }

回答2:

Yes, you can do this manually.

The basic idea is to track user's location with CLLocationManager and use it's data for placing and rotating annotation view on the map.

Here is the code. I'm omitting certain things that are not directly related to the question (e.g. I'm assuming that user have already authorized your app for location access, etc.), so you'll probably want to modify this code a little bit

ViewController.swift

import UIKit
import MapKit

class ViewController: UIViewController, CLLocationManagerDelegate, MKMapViewDelegate {
    @IBOutlet var mapView: MKMapView!
    lazy var locationManager: CLLocationManager = {
        let manager = CLLocationManager()
        manager.delegate = self
        return manager
    }()

    var userLocationAnnotation: UserLocationAnnotation!

    override func viewDidLoad() {
        super.viewDidLoad()

        locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation

        locationManager.startUpdatingHeading()
        locationManager.startUpdatingLocation()

        userLocationAnnotation = UserLocationAnnotation(withCoordinate: CLLocationCoordinate2D(), heading: 0.0)

        mapView.addAnnotation(userLocationAnnotation)
    }

    func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
        userLocationAnnotation.heading = newHeading.trueHeading
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        userLocationAnnotation.coordinate = locations.last!.coordinate
    }

    public func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
        if let annotation = annotation as? UserLocationAnnotation {
            let annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: "UserLocationAnnotationView") ?? UserLocationAnnotationView(annotation: annotation, reuseIdentifier: "UserLocationAnnotationView")
            return annotationView
        } else {
            return MKPinAnnotationView(annotation: annotation, reuseIdentifier: nil)
        }
    }

}

Here we are doing basic setup of the map view and starting to track user's location and heading with the CLLocationManager.

UserLocationAnnotation.swift

import UIKit
import MapKit

class UserLocationAnnotation: MKPointAnnotation {
    public init(withCoordinate coordinate: CLLocationCoordinate2D, heading: CLLocationDirection) {
        self.heading = heading

        super.init()
        self.coordinate = coordinate
    }

    dynamic public var heading: CLLocationDirection
}

Very simple MKPointAnnotation subclass that is capable of storing heading direction. dynamic keyword is the key thing here. It allows us to observe changes to the heading property with KVO.

UserLocationAnnotationView.swift

import UIKit
import MapKit

class UserLocationAnnotationView: MKAnnotationView {

    var arrowImageView: UIImageView!

    private var kvoContext: UInt8 = 13

    override public init(annotation: MKAnnotation?, reuseIdentifier: String?) {
        super.init(annotation: annotation, reuseIdentifier: reuseIdentifier)

        arrowImageView = UIImageView(image: #imageLiteral(resourceName: "Black_Arrow_Up.svg"))
        addSubview(arrowImageView)
        setupObserver()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

        arrowImageView = UIImageView(image: #imageLiteral(resourceName: "Black_Arrow_Up.svg"))
        addSubview(arrowImageView)
        setupObserver()
    }

    func setupObserver() {
        (annotation as? UserLocationAnnotation)?.addObserver(self, forKeyPath: "heading", options: [.initial, .new], context: &kvoContext)
    }

    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if context == &kvoContext {
            let userLocationAnnotation = annotation as! UserLocationAnnotation
            UIView.animate(withDuration: 0.2, animations: { [unowned self] in
                self.arrowImageView.transform = CGAffineTransform(rotationAngle: CGFloat(userLocationAnnotation.heading / 180 * M_PI))
            })
        }
    }

    deinit {
        (annotation as? UserLocationAnnotation)?.removeObserver(self, forKeyPath: "heading")
    }
}

MKAnnotationView subclass that does the observation of the heading property and then sets the appropriate rotation transform to it's subview (in my case it's just an image with the arrow. You can create more sophisticated annotation view and rotate only some part of it instead of the whole view.)

UIView.animate is optional. It is added to make rotation smoother. CLLocationManager is not capable of observing heading value 60 times per second, so when rotating fast, animation might be a little bit choppy. UIView.animate call solves this tiny issue.

Proper handling of coordinate value updates is already implemented in MKPointAnnotation, MKAnnotationView and MKMapView classes for us, so we don't have to do it ourselves.

回答3:

I solved this by adding a subview to the MKUserLocation annotationView, like so

func mapView(mapView: MKMapView, didAddAnnotationViews views: [MKAnnotationView]) {
if annotationView.annotation is MKUserLocation {
    addHeadingViewToAnnotationView(annotationView)
    }
}

func addHeadingViewToAnnotationView(annotationView: MKAnnotationView) {
    if headingImageView == nil {
        if let image = UIImage(named: "icon-location-heading-arrow") {
            let headingImageView = UIImageView()
            headingImageView.image = image
            headingImageView.frame = CGRectMake((annotationView.frame.size.width - image.size.width)/2, (annotationView.frame.size.height - image.size.height)/2, image.size.width, image.size.height)
            self.headingImageView = headingImageView
        }
    }

    headingImageView?.removeFromSuperview()
    if let headingImageView = headingImageView {
        annotationView.insertSubview(headingImageView, atIndex: 0)
    }

    //use CoreLocation to monitor heading here, and rotate headingImageView as required
}

回答4:

I wonder why no one offered a delegate solution. It does not rely on MKUserLocation but rather uses the approach proposed by @Dim_ov for the most part i.e. subclassing both MKPointAnnotation and MKAnnotationView (the cleanest and the most generic way IMHO). The only difference is that the observer is now replaced with a delegate method.

Create the delegate protocol:

protocol HeadingDelegate : AnyObject {
    func headingChanged(_ heading: CLLocationDirection)
}

Create MKPointAnnotation subclass that notifies the delegate. The headingDelegate property will be assigned externally from the view controller and triggered every time the heading property changes:

class Annotation : MKPointAnnotation {
    weak var headingDelegate: HeadingDelegate?
    var heading: CLLocationDirection {
        didSet {
            headingDelegate?.headingChanged(heading)
        }
    }

    init(_ coordinate: CLLocationCoordinate2D, _ heading: CLLocationDirection) {
        self.heading = heading
        super.init()
        self.coordinate = coordinate
    }
}

Create MKAnnotationView subclass that implements the delegate:

class AnnotationView : MKAnnotationView , HeadingDelegate {
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override init(annotation: MKAnnotation?, reuseIdentifier: String?) {
        super.init(annotation: annotation, reuseIdentifier: reuseIdentifier)
    }

    func headingChanged(_ heading: CLLocationDirection) {
        // For simplicity the affine transform is done on the view itself
        UIView.animate(withDuration: 0.1, animations: { [unowned self] in
            self.transform = CGAffineTransform(rotationAngle: CGFloat(heading / 180 * .pi))
        })
    }
}

Considering that your view controller implements both CLLocationManagerDelegate and MKMapViewDelegate there is very little left to do (not providing full view controller code here):

    // Delegate method of the CLLocationManager
    func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
        userAnnotation.heading = newHeading.trueHeading
    }

    // Delegate method of the MKMapView
    func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {        
        var annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: NSStringFromClass(Annotation.self))
        if (annotationView == nil) {
            annotationView = AnnotationView(annotation: annotation, reuseIdentifier: NSStringFromClass(Annotation.self))
        } else {
            annotationView!.annotation = annotation
        }

        if let annotation = annotation as? Annotation {
            annotation.headingDelegate = annotationView as? HeadingDelegate
            annotationView!.image = /* arrow image */
        }

        return annotationView
    }

The most important part is where the delegate property of the annotation (headingDelegate) is assigned with the annotation view object. This binds the annotation with it's view such that every time the heading property is modified the view's headingChanged() method is called.

NOTE: didSet{} and willSet{} property observers used here were first introduced in Swift 4.

来源：https://stackoverflow.com/questions/39762732/ios-10-heading-arrow-for-mkuserlocation-dot

标签

ios

mkmapview

ios10

mkuserlocation