Question

因此，我正在尝试制作一张地图，以便在我旅行时显示特定的纪念碑。我希望它在我在屏幕上移动地图时更新可用的纪念碑。我正在使用带有GET参数的php页面来返回我的数据库中可用的点数。我目前已将它设置为起点，但在拖动地图后我无法弄清楚如何更新它。我希望它能够根据地图的中心进行更新，无论哪里可能是dragend。这是带有JavaScript的地图页面。

<!DOCTYPE html >
  <head>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
    <meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
    <title>NGS Dynamic Map with Google Maps</title>
    <style>
      #main{
        height:90%;
      }
      /* 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;
      }
    </style>
  </head>

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



        function initMap() {
        var map = new google.maps.Map(document.getElementById('map'), {
          center: new google.maps.LatLng(30.27,-98.87),
          zoom: 12
        });
        var infoWindow = new google.maps.InfoWindow;
    var NewMapCenter = map.getCenter();
    var vlat = NewMapCenter.lat();
    var vlong = NewMapCenter.lng();


          // Change this depending on the name of your PHP or XML file
          downloadUrl('makePoints.php?lat=' + vlat + '&long=' + vlong, function(data) {
            var xml = data.responseXML;
            var markers = xml.documentElement.getElementsByTagName('marker');
            Array.prototype.forEach.call(markers, function(markerElem) {
              var id = markerElem.getAttribute('id');
              var name = markerElem.getAttribute('name');
              var county = markerElem.getAttribute('county');
              var state = markerElem.getAttribute('state');
          var elevation = markerElem.getAttribute('elevation');
          var data_source = markerElem.getAttribute('data_source');

              var point = new google.maps.LatLng(
                  parseFloat(markerElem.getAttribute('lat')),
                  parseFloat(markerElem.getAttribute('lng')));

              var infowincontent = document.createElement('div');
              var strong = document.createElement('strong');
              strong.textContent = "PID# " + name
              infowincontent.appendChild(strong);
              infowincontent.appendChild(document.createElement('br'));

              var text = document.createElement('text');
              text.textContent = county + " County"
              infowincontent.appendChild(text);
              infowincontent.appendChild(document.createElement('br'));

              var text = document.createElement('text');
              text.textContent = elevation + " (US Survey Ft.)"
              infowincontent.appendChild(text);
              infowincontent.appendChild(document.createElement('br'));


              var newlink = document.createElement('a');
              newlink.textContent = data_source
              newlink.setAttribute('target', '_new');
              newlink.setAttribute('href', data_source);
              infowincontent.appendChild(newlink);
              infowincontent.appendChild(document.createElement('br'));

              var marker = new google.maps.Marker({
                map: map,
                position: point
              });
              marker.addListener('click', function() {
                infoWindow.setContent(infowincontent);
                infoWindow.open(map, marker);
              });
            });
          });
        }



      function downloadUrl(url, callback) {
        var request = window.ActiveXObject ?
            new ActiveXObject('Microsoft.XMLHTTP') :
            new XMLHttpRequest;

        request.onreadystatechange = function() {
          if (request.readyState == 4) {
            request.onreadystatechange = doNothing;
            callback(request, request.status);
          }
        };

        request.open('GET', url, true);
        request.send(null);
      }

      function doNothing() {}
    </script>
    <script async defer
    src="https://maps.googleapis.com/maps/api/js?key=AIzaSyD_wB5WVi2nupVm9WzQ9C8Px_iYB1JZJv0&callback=initMap">
    </script>
  </body>
</html>

我想我可以保留我的downloadUrl参数的变量并在dragend事件上更新它们，这也会重新初始化调用和处理downloadUrl（）数据的函数。然后地图会更新，但我不确定这是实现它的正确方法。

此外，downloadUrl页面只需要通过GET传递的纬度/经度并访问我的数据库，然后抓住经过它的纬度/经度半径10英里范围内的所有内容。 php返回XML。我真的不太了解.js了解如何使这项工作。任何想法都将不胜感激。

Answer 1

你需要的是地图上dragend的事件监听器，重复你的PHP文件的ajax请求。在其自己的函数中调用该ajax请求。将map变量设为全局变量，以便可以在两个函数中访问它。

这样的事情：

var map;

function initMap() {
    map = new google.maps.Map(document.getElementById('map'), {
        center: new google.maps.LatLng(30.27, -98.87),
        zoom: 12
    });

    getPoints(30.27, -98.87);

    map.addListener('dragend', function() {
        var NewMapCenter = this.getCenter();
        var vlat = NewMapCenter.lat();
        var vlong = NewMapCenter.lng();
        getPoints(vlat, vlong);
    });
}

function getPoints(vlat, vlong) {
    downloadUrl('makePoints.php?lat=' + vlat + '&long=' + vlong, function(data) {
        var xml = data.responseXML;
        var markers = xml.documentElement.getElementsByTagName('marker');
        var infoWindow = new google.maps.InfoWindow();

        markers.forEach(function(markerElem) {
            var id = markerElem.getAttribute('id');
            var name = markerElem.getAttribute('name');
            var county = markerElem.getAttribute('county');
            var state = markerElem.getAttribute('state');
            var elevation = markerElem.getAttribute('elevation');
            var data_source = markerElem.getAttribute('data_source');

            var point = new google.maps.LatLng(
                parseFloat(markerElem.getAttribute('lat')),
                parseFloat(markerElem.getAttribute('lng')));

            var infowincontent = // ... etc

            var marker = new google.maps.Marker({
                map: map,
                position: point
            });
            marker.addListener('click', function() {
                infoWindow.setContent(infowincontent);
                infoWindow.open(map, marker);
            });
        });
    }); 
}

如何根据新位置

1 个答案: