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ios - 只有一个(自定义)注释从一组其他注释中旋转

转载 作者：搜寻专家 更新时间：2023-10-31 08:33:08 24 4
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我的应用程序即将进入最后阶段，它显示实时公交车 map 。所以，基本上，我有一个计时器，它定期从提供公交车实时位置的 xml 表中获取公交车的纬度和经度。我能够设置 xml 解析器，为公交车的运动设置动画并为公交车设置自定义(箭头)图像。

但是，问题是，从多条总线的数组中，我只能得到一条总线进行轮换。查看 xml 数据，它始终是旋转的 xml 表中的第一条总线。早些时候，我什至无法旋转单辆公共(public)汽车，所以用户“Good Doug”帮助了我，我能够让它工作。你可以在这里看到帖子:Custom annotation image rotates only at the beginning of the Program (Swift- iOS) .我尝试通过为每条总线制作一个 MKAnnotationView 数组来使用相同的解决方案。我不确定这是否是正确的方法。如果有人能帮我解决这个问题，我会很高兴:)

首先，XML 表是这样的(在这个例子中，有两辆车，所以我们只需要跟踪其中的两辆车):

<body>
        <vehicle id="3815" routeTag="connector" dirTag="loop" lat="44.98068" lon="-93.18071" secsSinceReport="3" predictable="true" heading="335" speedKmHr="12" passengerCount="16"/>
        <vehicle id="3810" routeTag="connector" dirTag="loop" lat="44.97313" lon="-93.24041" secsSinceReport="3" predictable="true" heading="254" speedKmHr="62" passengerCount="1"/>
</body>

这是我实现的一个单独的 Bus 类(在 Bus.swift 文件中)。这可能需要一些改进。

class Bus : MKPointAnnotation, MKAnnotation  {
    var oldCoord : CLLocationCoordinate2D!
    var addedToMap = false

    init(coord: CLLocationCoordinate2D) {
        self.oldCoord = coord
    }
}

这是我的 ViewController.swift 中的代码-

var busArray: [Bus!] = []           //Array to hold custom defined "Bus" types (from Bus.swift file)
var busViewArray : [MKAnnotationView?] = [nil, nil]                //Array to hold MKAnnotationView of each bus. We're assuming 2 buses are active in this case.
var vehicleCount = 0                // variable to hold the number of buses
var vehicleIndex = 0                // variable to check which bus the xml parser is currently on.
var trackingBusForTheVeryFirstTime = true

// My xml parser function:
func parser(parser: NSXMLParser!, didStartElement elementName: String!, namespaceURI: String!, qualifiedName qName: String!, attributes attributeDict: NSDictionary!) {
   if (elementName == "vehicle" ) {             
                let latitude = attributeDict["lat"]?.doubleValue                // Get latitude of current bus
                let longitude = attributeDict["lon"]?.doubleValue                // Get longitude of current bus
                let dir = attributeDict["heading"]?.doubleValue                        // Get direction of current bus

                var currentCoord = CLLocationCoordinate2DMake(latitude!, longitude!)                // Current coordinates of the bus

                // Checking the buses for the VERY FIRST TIME. This is usually the start of the program
                if (trackingBusForTheVeryFirstTime || vehicleCount == 0) {                  
                        let bus = Bus(coord: currentCoord)
                        self.busArray.append(bus)                        // Put current bus to the busArray
                        self.vehicleCount++                                        
                }
                else {        // UPDATE BUS Location. (Note: this is not the first time)

                        // If index exceeded count, that means number of buses changed, so we need to start over
                        if (self.vehicleIndex >= self.vehicleCount) {                         
                                self.trackingBusForTheVeryFirstTime = true                       
                                // Reset count and index for buses
                                self.vehicleCount = 0
                                self.vehicleIndex = 0
                                return
                        }

                        let oldCoord = busArray[vehicleIndex].oldCoord                   

                        if (oldCoord.latitude == latitude && oldCoord.longitude == longitude) {
                                // if oldCoordinates and current coordinates are the same, the bus hasn't moved. So do nothing.
                                return
                        }
                        else {                       
                                // Move and Rotate the bus:                       
                                UIView.animateWithDuration(0.5) {
                                        self.busArray[self.vehicleIndex].coordinate = CLLocationCoordinate2DMake(latitude!, longitude!)

                                        // if bus annotations have not been added to the map yet, add them:
                                        if (self.busArray[self.vehicleIndex].addedToMap == false) {
                                                self.map.addAnnotation(self.busArray[self.vehicleIndex])
                                                self.busArray[self.vehicleIndex].addedToMap = true
                                                return
                                        }

                                        if let pv = self.busViewArray[self.vehicleIndex] {
                                                pv.transform = CGAffineTransformRotate(self.map.transform, CGFloat(self.degreesToRadians(dir!)))         // Rotate bus
                                        }                          
                                }
                                if (vehicleIndex < vehicleCount - 1) 
                                        self.vehicleIndex++
                                }
                                else {
                                        self.vehicleIndex = 0
                                }
                                return     
                        }
                }
   }

这是我实现的 viewForAnnotation:

func mapView(mapView: MKMapView!, viewForAnnotation annotation: MKAnnotation!) -> MKAnnotationView! {

        let reuseId = "pin\(self.vehicleIndex)"
        busViewArray[self.vehicleIndex] = mapView.dequeueReusableAnnotationViewWithIdentifier(reuseId)

        if busViewArray[self.vehicleIndex] == nil {          
                self.busViewArray[self.vehicleIndex] = MKAnnotationView(annotation: annotation, reuseIdentifier: reuseId)       
                busViewArray[vehicleIndex]!.image = imageWithImage(UIImage(named:"arrow.png")!, scaledToSize: CGSize(width: 21.0, height: 21.0))     
                self.view.addSubview(busViewArray[self.vehicleIndex]!)
        }
        else {
                busViewArray[self.vehicleIndex]!.annotation = annotation
        }  
        return busViewArray[self.vehicleIndex]
}

我对我的 viewForAnnotation 实现表示怀疑。我也不确定是否可以使用 MKAnnotationView 数组。也许，我对注释 View 在 iOS 中的工作方式的理解是错误的。如果有人可以帮助我解决这个问题，我会很高兴，因为我已经坚持了一段时间。即使整体实现需要更改，我也很乐意尝试一下。这是问题的屏幕截图。

screenshot

再次请注意，所有巴士都出现在正确的位置并平稳移动，但只有其中一辆真正旋转。提前致谢。

最佳答案

我认为解析代码直接操作注释 View 是不合适的。你不知道它们是否可见，它们是否已经被实例化等等。 map View 负责管理注释 View ，而不是你。

如果您需要维护总线和注释之间的交叉引用，请这样做，但不要维护对注释 View 的引用。您的应用程序与注释的交互应仅限于注释本身。因此，创建一个具有 angle 属性的注解子类。 

class MyAnnotation : MKPointAnnotation {
    @objc dynamic var angle: CGFloat = 0.0
}

然后您可以让注释 View 子类“观察”自定义注释子类，随着注释的角度 变化而旋转。例如，在 Swift 4 中:

class MyAnnotationView : MKAnnotationView {

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

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

    // Remember, since annotation views can be reused, if the annotation changes,
    // remove the old annotation's observer, if any, and add new one's.

    override var annotation: MKAnnotation? {
        willSet { token = nil        }
        didSet  { addAngleObserver() }
    }

    // add observer

    var token: NSKeyValueObservation!

    private func addAngleObserver() {
        if let annotation = annotation as? MyAnnotation {
            transform = CGAffineTransform(rotationAngle: annotation.angle)
            token = annotation.observe(\.angle) { [weak self] annotation, _ in
                UIView.animate(withDuration: 0.25) {
                    self?.transform = CGAffineTransform(rotationAngle: annotation.angle)
                }
            }
        }
    }
}

或者在 Swift 3 中:

private var angleObserverContext = 0

class MyAnnotationView : MKAnnotationView {
    override init(annotation: MKAnnotation?, reuseIdentifier: String?) {
        super.init(annotation: annotation, reuseIdentifier: reuseIdentifier)
        addAngleObserver()
    }

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

    // add observer

    private func addAngleObserver() {
        if let annotation = annotation as? MyAnnotation {
            transform = CGAffineTransform(rotationAngle: annotation.angle)
            annotation.addObserver(self, forKeyPath: #keyPath(MyAnnotation.angle), options: [.new, .old], context: &angleObserverContext)
        }
    }

    // remove observer

    private func removeAngleObserver() {
        if let annotation = annotation as? MyAnnotation {
            annotation.removeObserver(self, forKeyPath: #keyPath(MyAnnotation.angle))
        }
    }

    // remember to remove observer when annotation view is deallocated

    deinit {
        removeAngleObserver()
    }

    // Remember, since annotation views can be reused, if the annotation changes,
    // remove the old annotation's observer, if any, and add new one's.

    override var annotation: MKAnnotation? {
        willSet { removeAngleObserver() }
        didSet  { addAngleObserver()    }
    }

    // Handle observation events for the annotation's `angle`, rotating as appropriate

    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        guard context == &angleObserverContext else {
            super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
            return
        }

        UIView.animate(withDuration: 0.5) {
            if let angleNew = change![.newKey] as? CGFloat {
                self.transform = CGAffineTransform(rotationAngle: angleNew)
            }
        }
    }
}

现在，您的应用程序可以维护对已添加到 map 的注释的引用，并设置它们的角度，这将在 map View 中以适当的方式可视化表示。

还有一个使用它的快速而肮脏的例子:

class ViewController: UIViewController {

    @IBOutlet weak var mapView: MKMapView!

    var annotation = MyAnnotation()

    private let reuseIdentifer = Bundle.main.bundleIdentifier! + ".annotation"

    private lazy var manager: CLLocationManager = {
        let manager = CLLocationManager()
        manager.delegate = self
        manager.desiredAccuracy = kCLLocationAccuracyBest
        return manager
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        mapView.register(MyAnnotationView.self, forAnnotationViewWithReuseIdentifier: reuseIdentifer)

        manager.requestWhenInUseAuthorization()
        manager.startUpdatingHeading()
        manager.startUpdatingLocation()

        mapView.addAnnotation(annotation)
    }

}

extension ViewController: MKMapViewDelegate {
    func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
        if annotation is MKUserLocation { return nil }

        return mapView.dequeueReusableAnnotationView(withIdentifier: reuseIdentifer, for: annotation)
    }
}

extension ViewController: CLLocationManagerDelegate {

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        guard let location = locations.last,
            location.horizontalAccuracy >= 0 else {
                return
        }
        annotation.coordinate = location.coordinate
    }

    func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
        guard newHeading.headingAccuracy >= 0 else { return }
        annotation.angle = CGFloat(newHeading.trueHeading * .pi / 180)
    }
}

参见 previous revision of this answer以 Swift 2 为例。

关于ios - 只有一个(自定义)注释从一组其他注释中旋转，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33457226/

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