javascript - this.setMap() 不适用于自定义叠加层

Question

我正在为 Google map 编写自定义叠加层。我有很多经纬度点，我想要带有指向和来自它们的箭头的图像。我正在关注 Google 的自定义叠加层教程 (https://developers.google.com/maps/documentation/javascript/overlays#CustomOverlays)。

在我的覆盖层的“构造函数”中，此行失败:'this.setMap(this.map_);'

我需要做什么才能让它发挥作用？

这是我的叠加层的“构造函数”。虚线位于底部。当我测试时，所有对“警报”的调用都在那里。最后一次调用未到达，这就是为什么我认为“this.setMap()”不起作用。

 //This serves as a constructor for a link overlay
 function LinkOverlay(startNodeCoordinates, endNodeCoordinates, map)
 {
    alert("constructor start");
    this.map_ = map;

    //These are the lat-long coordinates of where the link starts and ends
    this.startNodeCoordinates_ = startNodeCoordinates;
    this.endNodeCoordinates_ = endNodeCoordinates;

    alert("constructor coordinates stored");

    // We define a property to hold the image's
    // div. We'll actually create this div
    // upon receipt of the add() method so we'll
    // leave it null for now.
    this.div_ = null;

    alert("constructor div saved");

    //We need to know if we draw the arrow up or down and left or right.
    //We calculate this by finding the bearing between the two nodes. If
    //the bearing is N to NE, then the arrow goes up and to the right,
    //for example. If the bearing is E to SE, then the arrow goes down
    //and to the right, and so on.

    //Calculate bearing
    /*
     * This algorithm determines the bearing (or angle) between two coordinate points.
     * It was adapted from http://www.movable-type.co.uk/scripts/latlong.html
     */
    alert("constructor calculating bearing")
    this.bearing_ = null;
    var lat1 = this.startNodeCoordinates_.lat();
    var lat2 = this.endNodeCoordinates_.lat();
    var dLon = this.startNodeCoordinates_.lng() - this.endNodeCoordinates_.lng();
    var y = Math.sin(dLon) * Math.cos(lat2);
    var x = Math.cos(lat1)*Math.sin(lat2) -
        Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
    this.bearing_ = Math.atan2(y, x);

    alert("constructor bearing found (bearing = " + this.bearing_ + ")");

    this.arrowUp_ = null;
    this.arrowRight_ = null;
    this.image_ = null;

    alert("constructor picking image");

    if((this.bearing_ >= 0 && this.bearing_ < (Math.PI * 0.5)) || this.bearing_ == (Math.PI * 2))
    {
        alert("constructor NE");
        //If bearing is N to NE, the arrow goes up and to the right
        this.arrowUp_ = new Boolean(true);
        this.arrowRight_ = new Boolean(true);
        this.image_ = "../../Content/map_images/link_overlay/up_right_black.png";
    }
    else if(this.bearing_ >= (Math.PI * 0.5) && this.bearing_ < Math.PI)
    {
        alert("constructor SE");
        //If bearing is E to SE, the arrow goes down and to the right
        this.arrowUp_ = new Boolean(false);
        this.arrowRight_ = new Boolean(true);
        this.image_ = "../../Content/map_images/link_overlay/down_right_black.png";
    }
    else if(this.bearing_ >= Math.PI && this.bearing_ < (Math.PI * 1.5))
    {
        alert("constructor SW");
        //If bearing is S to SW, the arrow goes down and to the left
        this.arrowUp_ = new Boolean(false);
        this.arrowRight_ = new Boolean(false);
        this.image_ = "../../Content/map_images/link_overlay/down_left_black.png";
    }
    else
    {
        alert("constructor NW");
        //If bearing is W to NW, the arrow goes up and to the left
        this.arrowUp_ = new Boolean(true);
        this.arrowRight_ = new Boolean(false);
        this.image_ = "../../Content/map_images/link_overlay/up_left_black.png";
    }

    alert("constructor adding to map");

    // Explicitly call setMap() on this overlay
    this.setMap(this.map_);

    alert("constructor end");
 }

 //This "subclasses" a link overlay from Google Map's OverlayView class
 LinkOverlay.prototype = new google.maps.OverlayView();

这是创建新 LinkOverlays 的代码(采用 Razor 语法):

@:var startNodeCoordinates = new google.maps.LatLng('@startNode.Latitude', '@startNode.Longitude');
@:var endNodeCoordinates = new google.maps.LatLng('@endNode.Latitude', '@endNode.Longitude');
@:var routeLine = new LinkOverlay(startNodeCoordinates, endNodeCoordinates, networkMap);

Answer 1

我也遇到了同样的问题。我使用"new"来实例化我的自定义覆盖层来修复它。在您的情况下，您确定在实例化覆盖层时使用:

linkOverlay = new LinkOverlay(s, e, map)