谷歌地图V3：定期更新标记

Question

我已经按照谷歌地图上的PHP/MYSQL教程发现here。

我希望标记每5秒左右从数据库更新一次。

这是我的理解，我需要使用Ajax周期性更新的标志，但我努力理解在哪里添加功能以及在何处使用的setTimeout（）等

所有其他的例子我我发现并没有真正解释发生了什么，一些有用的指导将会非常棒！

这是我的代码（同谷歌例如一些VAR变化）：

function load() { 
    var map = new google.maps.Map(document.getElementById("map"), { 
    center: new google.maps.LatLng(37.80815648152641, 140.95355987548828), 
    zoom: 13, 
    mapTypeId: 'roadmap' 
    }); 
    var infoWindow = new google.maps.InfoWindow; 

    // Change this depending on the name of your PHP file 

    downloadUrl("nwmxml.php", function(data) { 
    var xml = data.responseXML; 
    var markers = xml.documentElement.getElementsByTagName("marker"); 
    for (var i = 0; i < markers.length; i++) { 
     var host = markers[i].getAttribute("host"); 
     var type = markers[i].getAttribute("active"); 
     var lastupdate = markers[i].getAttribute("lastupdate"); 
     var point = new google.maps.LatLng(
      parseFloat(markers[i].getAttribute("lat")), 
      parseFloat(markers[i].getAttribute("lng"))); 
     var html = "<b>" + "Host: </b>" + host + "<br>" + "<b>Last Updated: </b>" + lastupdate + "<br>"; 
     var icon = customIcons[type] || {}; 
     var marker = new google.maps.Marker({ 
     map: map, 
     position: point, 
     icon: icon.icon, 
     shadow: icon.shadow 
     }); 
     bindInfoWindow(marker, map, infoWindow, html); 

    } 

    }); 
} 

function bindInfoWindow(marker, map, infoWindow, html) { 
    google.maps.event.addListener(marker, 'click', function() { 
    infoWindow.setContent(html); 
    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() {} 

我希望有人能帮帮我！

Answer 1

请注意我没有测试过这个，因为我没有使用XML得心应手分贝

所有你需要你的load（）函数分成初始化地图&负载标记上domready中函数的第一个并且稍后您将使用该函数来处理xml &以更新地图。这需要完成，以便在每次加载时都不重新初始化映射。

其次，您需要决定如何处理已在地图上绘制的标记。为此，您需要在将它们添加到地图时将它们添加到数组中。在第二次更新时，您可以选择重新绘制标记（重建数组）或仅更新现有数组。我的例子显示了只需从屏幕上清除旧标记的情况（这更简单）。

//global array to store our markers 
    var markersArray = []; 
    var map; 
    function load() { 
     map = new google.maps.Map(document.getElementById("map"), { 
      center : new google.maps.LatLng(37.80815648152641, 140.95355987548828), 
      zoom : 13, 
      mapTypeId : 'roadmap' 
     }); 
     var infoWindow = new google.maps.InfoWindow; 

     // your first call to get & process inital data 

     downloadUrl("nwmxml.php", processXML); 
    } 

    function processXML(data) { 
     var xml = data.responseXML; 
     var markers = xml.documentElement.getElementsByTagName("marker"); 
     //clear markers before you start drawing new ones 
     resetMarkers(markersArray) 
     for(var i = 0; i < markers.length; i++) { 
      var host = markers[i].getAttribute("host"); 
      var type = markers[i].getAttribute("active"); 
      var lastupdate = markers[i].getAttribute("lastupdate"); 
      var point = new google.maps.LatLng(parseFloat(markers[i].getAttribute("lat")), parseFloat(markers[i].getAttribute("lng"))); 
      var html = "<b>" + "Host: </b>" + host + "<br>" + "<b>Last Updated: </b>" + lastupdate + "<br>"; 
      var icon = customIcons[type] || {}; 
      var marker = new google.maps.Marker({ 
       map : map, 
       position : point, 
       icon : icon.icon, 
       shadow : icon.shadow 
      }); 
      //store marker object in a new array 
      markersArray.push(marker); 
      bindInfoWindow(marker, map, infoWindow, html); 


     } 
      // set timeout after you finished processing & displaying the first lot of markers. Rember that requests on the server can take some time to complete. SO you want to make another one 
      // only when the first one is completed. 
      setTimeout(function() { 
       downloadUrl("nwmxml.php", processXML); 
      }, 5000); 
    } 

//clear existing markers from the map 
function resetMarkers(arr){ 
    for (var i=0;i<arr.length; i++){ 
     arr[i].setMap(null); 
    } 
    //reset the main marker array for the next call 
    arr=[]; 
} 
    function bindInfoWindow(marker, map, infoWindow, html) { 
     google.maps.event.addListener(marker, 'click', function() { 
      infoWindow.setContent(html); 
      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); 
    } 

Answer 2

setInterval(function() { 
    downloadUrl("conection/cargar_tecnicos.php", function(data) { 

     var xml = data.responseXML; 
     markers = xml.documentElement.getElementsByTagName("marker"); 
     removeAllMarkers(); 
     for (var i = 0; i < markers.length; i++) { 
       var name = markers[i].getAttribute("name"); 
      var fecha = markers[i].getAttribute("fecha"); 
      var id_android = markers[i].getAttribute("id_android"); 
      var celular = markers[i].getAttribute("celular"); 
      var id = markers[i].getAttribute("id"); 
      var logo = markers[i].getAttribute("logo"); 
      var type = markers[i].getAttribute("type"); 
      var point = new google.maps.LatLng(
        parseFloat(markers[i].getAttribute("lat")), 
        parseFloat(markers[i].getAttribute("lng"))); 

      var html = "<div class='infowindow'>" 
         +"<br/><div style='text-align:center;'><img src="+logo+"><br/>"  
         +"<b>" + name + "</b></div><br/>" 
         +"<br/><label><b>Celular:</b></label>" + celular+"" 
         +"<br/><label><b>Id Android:</b></label>" + id_android+"" 
         +"<br/><label><b>Fecha y Hora:</b></label>" + fecha+"" 
         +"<br/><br/><div style='text-align:center;'><a><input style=';' id='pop' type='image' value='"+id+"' class='ASD' img src='img/vermas.png' title='Detalles'/></a></div></div>"; 
      var icon = customIcons[type] || {}; 
      marker[i] = new google.maps.Marker({ 
       position: point, 
       icon: icon.icon, 
       shadow: icon.shadow, 
       title:name 
      }); 

      openInfoWindow(marker[i], map, infoWindow, html); 
      marker[i].setMap(map); 
     } 
    }); 

},10000); 
} 
function removeAllMarkers(){// removes all markers from map 
    for(var i = 0; i < marker.length; i++){ 
      marker[i].setMap(null); 
} 
}