ios - GMSMutablePath 删除/替换坐标问题，折线

Question

我正在构建一个应用程序，该应用程序使用 Google Maps Directions API 为我提供路线折线，以便我可以在我的 mapView 上向用户显示。有点像 Google Maps turn-by-turn 服务，但在我的应用程序中。

这张 map 上的标记是 Google Directions 给出的折线的坐标

所有上述坐标(标记)都存储在变量“路径”中，这是一个 GMSMutablePath。每当用户的位置靠近路径上的坐标时(按顺序移动，所以首先坐标 0，然后 1..)我通过 removeCoordinateAtIndex() 从路径中删除该坐标，以便多段线消失(例如:从标记 0 到标记 1) 来 self 的 map 。目的是我希望多段线始终从用户位置开始显示，而不是我的路线起点。

问题: 但是，我不确定为什么，但是导致 removeCoordinateAtIndex() 的 if 语句似乎只在我在路径(我的 GMSMutablePath)上的索引 0.. 2.. 4(偶数)上删除，所以在两者之间跳过一个.

这是我的 locationManager 函数

pathIndex = 0

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    let location = locations[locations.count - 1]

    /*
        For each GPS update, check location of user against next waypoint 
    on route. If distance is within 6 meters (18 feet), increment pathIndex 
    and now draw polyline from current location to NEXT waypoint (if there  
    is one), and then compare user location to NEXT waypoint again, etc.
    */

    //Replace polyline to start display from where you are
    path.replaceCoordinateAtIndex(UInt(0), withCoordinate: CLLocationCoordinate2DMake(location.coordinate.latitude, location.coordinate.longitude))
    polyline.path = path

    //Get distance from current to next waypoint in path
    let waypoint = CLLocation(latitude: path.coordinateAtIndex(UInt(pathIndex)).latitude, longitude: path.coordinateAtIndex(UInt(pathIndex)).longitude) //Coordinate of next waypoint
    let locToWaypoint = location.distanceFromLocation(waypoint) //Returns distance in meters
    print("dist: ", locToWaypoint, ", index: ", pathIndex)

    //If closer than 6 meters, remove polyline of that segment from map
    if (locToWaypoint < 6) {
        //If not on last step
        if (pathIndex < Int(path.count()) - 1) {
            pathIndex++
            //Remove last path
            print("Removing: ", path.coordinateAtIndex(UInt(0)))
            path.removeCoordinateAtIndex(UInt(0))

        }
    }
}

我感觉它正在跳过删除，因为

中的 0

path.removeCoordinateAtIndex(Uint(0))
path.replaceCoordinateAtIndex(UInt(0), withCoordinate: ...)

但是在改变它之后，我仍然遇到同样的问题，所以我认为这可能是另一回事。

这是调试日志。请注意，只有第一次和第三次调用会删除坐标，第二次调用会删除坐标。当我将 pathIndex 设置为 1 时，这会更改为第二次和第四次调用(中间总是跳过一次):

dist: 0.0 , index:  0       
Removing:  CLLocationCoordinate2D(latitude: 36.131648, longitude: -80.275542)  //First time, so is removed. This is the origin.
dist: 40.3950268964149 , index:  1     //Now showing dist to next waypoint

dist: 14.8659227375514 , index:  1  //Second time; NOT removed. Somehow it just skips the coordinate at the index and goes on to calculate the distance to the NEXT waypoint (thus 14.86)

dist: 1.34445248711346 , index:  1  
Removing:  CLLocationCoordinate2D(latitude: 36.131931, longitude: -80.2758)   //Third time, IS removed.
dist: 45.4634994640154 , index:  2     //Now showing dist to next waypoint

它在做什么，让它跳过第二个航路点/坐标？

PS: 当我调用 removeCoordinateAtIndex(0) 时，是否所有内容都向下滑动到一个位置？例如，如果删除前的路径是:[0, 1, 2, 3]，删除后的路径将是:[1, 2, 3](如此调整大小)，或者实际上 [ , 1, 2, 3] 与索引 0 处的空白？

Answer 1

发现问题了!

线

let waypoint = CLLocation(latitude: path.coordinateAtIndex(UInt(pathIndex)).latitude, longitude: path.coordinateAtIndex(UInt(pathIndex)).longitude)

应该阅读:

let waypoint = CLLocation(latitude: path.coordinateAtIndex(UInt(1)).latitude, longitude: path.coordinateAtIndex(UInt(1)).longitude)

相反。注意 pathIndex -> 1 的变化，所以现在 distanceFromLocation 将始终只与路径中的下一个坐标进行比较。