如何沿多段线精确移动标记？

Question

Marker Movement from source to destination

显示标记移动的图像，它是一条直线，标记仅在一个方向上。我想沿着折线移动我的标记，标记方向应该随着折线方向而改变。如何实现这一目标。我现在的代码是这样的：

class MapScreenVC: BaseVC {

var path = GMSMutablePath()
var arrayCoordinates : [CLLocationCoordinate2D] = []
var destCoord = CLLocationCoordinate2D()
var marker = GMSMarker()
var mapView : GMSMapView? = nil
override func viewDidLoad() {
    super.viewDidLoad()

    let camera = GMSCameraPosition.camera(withLatitude: 53.4545, longitude: -2.1811, zoom: 14)
    mapView = GMSMapView.map(withFrame: .zero, camera: camera)
    marker = GMSMarker()
    marker.position = CLLocationCoordinate2DMake(53.4387, -2.1827)
    marker.title = "Source"
    marker.snippet = "Source"
    marker.icon = UIImage(named: "car")
    marker.map = mapView



    let DestinationMarker = GMSMarker()
    self.destCoord = CLLocationCoordinate2DMake(53.4645, -2.1873)
    DestinationMarker.position = CLLocationCoordinate2DMake(53.4643, -2.1869)
    DestinationMarker.title = "Destination"
    DestinationMarker.snippet = "Destination"
    DestinationMarker.icon = UIImage(named: "home")
    DestinationMarker.map = mapView

// 折线

    path.addLatitude(53.4395, longitude:-2.1834)
    path.addLatitude(53.4403, longitude:-2.1854)
    path.addLatitude(53.4414, longitude:-2.1852)
    path.addLatitude(53.4428, longitude:-2.1832)
    path.addLatitude(53.4442, longitude:-2.1818)
    path.addLatitude(53.4449, longitude:-2.1801)
    path.addLatitude(53.4478, longitude:-2.1793)
    path.addLatitude(53.4504, longitude:-2.1798)
    path.addLatitude(53.4526, longitude:-2.1806)
    path.addLatitude(53.4545, longitude:-2.1811)
    path.addLatitude(53.4564, longitude:-2.1811)
    path.addLatitude(53.4584, longitude:-2.1811)
    path.addLatitude(53.4601, longitude:-2.1811)
    path.addLatitude(53.4617, longitude:-2.1821)
    path.addLatitude(53.4630, longitude:-2.1829)
    path.addLatitude(53.4632, longitude:-2.1851)
    path.addLatitude(53.4635, longitude:-2.1869)
    path.addLatitude(53.4638, longitude:-2.1882)
    path.addLatitude(53.4645, longitude:-2.1873)


    let polyline = GMSPolyline(path: path)
    polyline.strokeColor = .blue
    polyline.strokeWidth = 6.0
    polyline.geodesic = true
    polyline.map = mapView
    updateMarker(coordinates: destCoord)
    view = mapView
}

func updateMarker(coordinates: CLLocationCoordinate2D) {
    CATransaction.begin()
    CATransaction.setAnimationDuration(10.0)
    marker.position = coordinates
    CATransaction.commit()
}

}

Answer 1

我不熟悉可以为您提供此功能的库或类似库，因此我将概述一种手动方法，您可以使用它来轻松地完成此操作。

要在折线上移动标记，您需要计算标记从每个点到达下一个点所需的步数。
一种选择是对定义折线的每条线执行以下操作：
1）每2个点定义一条线f(x) = ax + b 如果您在计算直线的斜率时需要帮助，可以进一步阅读 here（上式中的 a）

2) 定义标记到达该行末尾所采取的步骤。您可以将线的长度除以一个常数，这将得到一个常数 step。这并不理想，因为跨短线和长线需要相同数量的步骤，但这是一个开始。另请注意，2 lat/lng 点之间的距离在球体上，并不像二维中那样简单。查看 https://en.wikipedia.org/wiki/Haversine_formula 了解更多信息。

3) 将marker放在第一个点(x1,y1)上，然后移动到(x1+step, f(x1+step)).
你需要判断在线上是向左移动还是向右移动。

4) 每次移动标记后，检查是否到达当前行的终点，然后重新开始下一行。

如何沿多段线精确移动标记？

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