如何使对象回到java map中的起点

分类：编程问答

如何解决如何使对象回到java map中的起点

我想做一些类似于公共汽车跟踪的东西，它绕着一个多边形移动，每秒移动 2 米回到起点。并且每秒对象（？）点坐标。

我什至不知道如何开始。请帮帮我。

多边形代码：

    function initMap() {
        map = new google.maps.Map(document.getElementById("map"),{
            zoom: 12,center: { lat: 0.5164426,lng: 101,4574499 },mapTypeId: "terrain",});
        
        const triangleCoords = [
            { lat: 0.5022181713704478,lng: 101.41882830662435 },{ lat: 0.4975231087415325,lng: 101.39433139688956 },{ lat: 0.5103834896305101,lng: 101.39412725597509 },{ lat: 0.5169157367830446,lng: 101.39923077883651 },{ lat: 0.5350835135799168,lng: 101.4035177380401 },{ lat: 0.5348793815517918,lng: 101.41984901119662 },];
        
        const bermudaTriangle = new google.maps.Polygon({
            paths: triangleCoords,strokeColor: "#0000FF",strokeOpacity: 1,strokeWeight: 2,fillColor: "#FF6633",fillOpacity: 0.35,});
        
        bermudaTriangle.setMap(map);
        bermudaTriangle.addListener("click",showArrays);
        infoWindow = new google.maps.InfoWindow();

基本上如何从 lat: 0.5022181713704478,lng: 101.41882830662435 返回到 lat: 0.5022181713704478,lng: 101.418682330

我的预期：http://www.geocodezip.com/v3_animate_marker_directions.html 但它有 6 点陈述和无休止的移动

解决方法

您发布的代码有几个问题：

  1. : lng 上的 map 之后没有 center：`
center: { lat: 0.5164426,lng 101,4574499 },

应该是：

center: { lat: 0.5164426,lng: 101,
  1. fillColor: "#FF6633" 中的 PolygonOptions 后没有逗号
  2. 在 PolygonOptions panths 应该是 paths
  3. 为了与 my example 保持一致，您需要一个 Polyline（而不是一个 Polygon），这意味着您需要添加最后一个点以完成路径：
  const triangleCoords = [{
      lat: 0.5022181713704478,lng: 101.41882830662435
    },{
      lat: 0.4975231087415325,lng: 101.39433139688956
    },{
      lat: 0.5103834896305101,lng: 101.39412725597509
    },{
      lat: 0.5169157367830446,lng: 101.39923077883651
    },{
      lat: 0.5350835135799168,lng: 101.4035177380401
    },{
      lat: 0.5348793815517918,lng: 101.41984901119662
    },{ // duplicate of first point
      lat: 0.5022181713704478,];

proof of concept fiddle

为了防止地图中心改变，删除改变中心的代码（一个map.setCenter实例，两个map.panTo实例）：
fiddle where map center not modified

screenshot of resulting map

要保持标记围绕循环，请通过调用 animate(0) 更改“结束”条件以重新开始动画：

function animate(d) {
  if (d > eol) {
    map.panTo(polyline.getPath().getAt(polyline.getPath().getLength() - 1));
    marker.setPosition(polyline.getPath().getAt(polyline.getPath().getLength() - 1));
    // continuous loop
    animate(0);
    return;
  }

live example

代码片段：

var polyline,marker;

function initMap() {
  addEpolyFunc();
  map = new google.maps.Map(document.getElementById("map"),{
    zoom: 12,center: {
      lat: 0.5164426,lng: 101.4574499
    },mapTypeId: "terrain",});

  const triangleCoords = [{
      lat: 0.5022181713704478,{
      lat: 0.5022181713704478,];

  const bermudaTriangle = new google.maps.Polygon({
    paths: triangleCoords,strokeColor: "#0000FF",strokeOpacity: 1,strokeWeight: 2,fillColor: "#FF6633",fillOpacity: 0.35,});

  bermudaTriangle.setMap(map);
  infoWindow = new google.maps.InfoWindow();
  polyline = new google.maps.Polyline({
    // map: map,path: triangleCoords,});
  marker = new google.maps.Marker({
    position: polyline.getPath().getAt(0),map: map
  })

  startAnimation();
}
var step = 50; // 5; // metres
var tick = 100; // milliseconds
var eol;
var k = 0;
var stepnum = 0;
var speed = "";
var lastVertex = 1;


//=============== animation functions ======================
function updatePoly(d) {
  // Spawn a new polyline every 20 vertices,because updating a 100-vertex poly is too slow
  if (poly2.getPath().getLength() > 20) {
    poly2 = new google.maps.Polyline([polyline.getPath().getAt(lastVertex - 1)]);
  }

  if (polyline.GetIndexAtDistance(d) < lastVertex + 2) {
    if (poly2.getPath().getLength() > 1) {
      poly2.getPath().removeAt(poly2.getPath().getLength() - 1)
    }
    poly2.getPath().insertAt(poly2.getPath().getLength(),polyline.GetPointAtDistance(d));
  } else {
    poly2.getPath().insertAt(poly2.getPath().getLength(),polyline.getPath().getAt(polyline.getPath().getLength() - 1));
  }
}


function animate(d) {
  if (d > eol) {
    map.panTo(polyline.getPath().getAt(polyline.getPath().getLength() - 1));
    marker.setPosition(polyline.getPath().getAt(polyline.getPath().getLength() - 1));
    // continuous loop
    animate(0);
    return;
  }
  var p = polyline.GetPointAtDistance(d);
  map.panTo(p);
  marker.setPosition(p);
  updatePoly(d);
  timerHandle = setTimeout("animate(" + (d + step) + ")",tick);
}


function startAnimation() {
  eol = google.maps.geometry.spherical.computeLength(polyline.getPath());
  map.setCenter(polyline.getPath().getAt(0));
  poly2 = new google.maps.Polyline({
    path: [polyline.getPath().getAt(0)],strokeWeight: 10
  });
  setTimeout("animate(50)",2000); // Allow time for the initial map display
}

function addEpolyFunc() {
  //=============== ~animation funcitons =====================
  // from epoly_v3.js
  // modified to use geometry library for length of line segments
  // === A method which returns the Vertex number at a given distance along the path ===
  // === Returns null if the path is shorter than the specified distance ===
  google.maps.Polyline.prototype.GetIndexAtDistance = function(metres) {
    // some awkward special cases
    if (metres == 0) return this.getPath().getAt(0);
    if (metres < 0) return null;
    var dist = 0;
    var olddist = 0;
    for (var i = 1;
      (i < this.getPath().getLength() && dist < metres); i++) {
      olddist = dist;
      dist += google.maps.geometry.spherical.computeDistanceBetween(this.getPath().getAt(i),this.getPath().getAt(i - 1));
    }
    if (dist < metres) {
      return null;
    }
    return i;
  }
  // === A method which returns a GLatLng of a point a given distance along the path ===
  // === Returns null if the path is shorter than the specified distance ===
  google.maps.Polyline.prototype.GetPointAtDistance = function(metres) {
    // some awkward special cases
    if (metres == 0) return this.getPath().getAt(0);
    if (metres < 0) return null;
    if (this.getPath().getLength() < 2) return null;
    var dist = 0;
    var olddist = 0;
    for (var i = 1;
      (i < this.getPath().getLength() && dist < metres); i++) {
      olddist = dist;
      dist += google.maps.geometry.spherical.computeDistanceBetween(this.getPath().getAt(i),this.getPath().getAt(i - 1));
    }
    if (dist < metres) {
      return null;
    }
    var p1 = this.getPath().getAt(i - 2);
    var p2 = this.getPath().getAt(i - 1);
    var m = (metres - olddist) / (dist - olddist);
    return new google.maps.LatLng(p1.lat() + (p2.lat() - p1.lat()) * m,p1.lng() + (p2.lng() - p1.lng()) * m);
  }
  // === A method which returns the length of a path in metres ===
  google.maps.Polyline.prototype.Distance = function() {
    var dist = 0;
    for (var i = 1; i < this.getPath().getLength(); i++) {
      dist += google.maps.geometry.spherical.computeDistanceBetween(this.getPath().getAt(i),this.getPath().getAt(i - 1));
    }
    return dist;
  }
}
/* Always set the map height explicitly to define the size of the div
       * element that contains the map. */

#map {
  height: 100%;
}


/* Optional: Makes the sample page fill the window. */

html,body {
  height: 100%;
  margin: 0;
  padding: 0;
}
<!DOCTYPE html>
<html>

<head>
  <title>Simple Polygon</title>
  <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
  <script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk&callback=initMap&libraries=geometry&v=weekly" defer></script>
  <!-- jsFiddle will insert css and js -->
</head>

<body>
  <div id="map"></div>
</body>

</html>

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