谷歌地图API：在特定区域从数据库搜索标记。

Question

谷歌地图API：在特定区域从数据库搜索标记。

4

我已经设置了谷歌地图API，从MySQL数据库加载数据并显示标记。我面临的问题是无论我在搜索位置字段中输入什么，所有标记都会同时显示出来..............我想只显示搜索区域和该区域内的标记。它不应该一次性显示所有标记，而只显示搜索区域内的标记。我的意思是我想将地图缩放到搜索区域。当前，如果我只有一个标记，地图会缩放以显示该标记，但如果我有多个标记，则地图会缩小以显示所有标记。这是我正在处理的地图"http://funfeat.com/clients/gmap/gmap3.html"。现在，我将标记设置得非常远，但地图仍然通过缩小来显示所有标记。

gmap.php是提供来自MySQL数据库的XML结果的文件。以下代码是我用来显示地图的：

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="content-type" content="text/html; charset=utf-8"/>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
    <title>Google Maps AJAX + mySQL/PHP Example</title>
    <script src="http://maps.googleapis.com/maps/api/js?sensor=false"
            type="text/javascript"></script>
    <script type="text/javascript">
    //<![CDATA[
    var map;
    var markers = [];
    var infoWindow;
    var locationSelect;

    function load() {
      map = new google.maps.Map(document.getElementById("map"), {
        center: new google.maps.LatLng(40, -100),
        zoom: 10,
        mapTypeId: 'roadmap',
        mapTypeControlOptions: {style: google.maps.MapTypeControlStyle.DROPDOWN_MENU}
      });
      infoWindow = new google.maps.InfoWindow();

      locationSelect = document.getElementById("locationSelect");
      locationSelect.onchange = function() {
        var markerNum = locationSelect.options[locationSelect.selectedIndex].value;
        if (markerNum != "none"){
          google.maps.event.trigger(markers[markerNum], 'click');
        }
      };
   }

   function searchLocations() {
     var address = document.getElementById("addressInput").value;
     var geocoder = new google.maps.Geocoder();
     geocoder.geocode({address: address}, function(results, status) {
       if (status == google.maps.GeocoderStatus.OK) {
        searchLocationsNear(results[0].geometry.location);
       } else {
         alert(address + ' not found');
       }
     });
   }

   function clearLocations() {
     infoWindow.close();
     for (var i = 0; i < markers.length; i++) {
       markers[i].setMap(null);
     }
     markers.length = 0;

     locationSelect.innerHTML = "";
     var option = document.createElement("option");
     option.value = "none";
     option.innerHTML = "See all results:";
     locationSelect.appendChild(option);
   }

   function searchLocationsNear(center) {
     clearLocations();

     var radius = document.getElementById('radiusSelect').value;
     var searchUrl = 'gmap.php?lat=' + center.lat() + '&lng=' + center.lng() + '&radius=' + radius;
     downloadUrl(searchUrl, function(data) {
       var xml = parseXml(data);
       var markerNodes = xml.documentElement.getElementsByTagName("marker");
       var bounds = new google.maps.LatLngBounds();
       for (var i = 0; i < markerNodes.length; i++) {
         var name = markerNodes[i].getAttribute("name");
         var address = markerNodes[i].getAttribute("address");
         var distance = parseFloat(markerNodes[i].getAttribute("distance"));
         var latlng = new google.maps.LatLng(
              parseFloat(markerNodes[i].getAttribute("lat")),
              parseFloat(markerNodes[i].getAttribute("lng")));

         createOption(name, distance, i);
         createMarker(latlng, name, address);
         bounds.extend(latlng);
       }
       map.fitBounds(bounds);
       locationSelect.style.visibility = "visible";
       locationSelect.onchange = function() {
         var markerNum = locationSelect.options[locationSelect.selectedIndex].value;
         google.maps.event.trigger(markers[markerNum], 'click');
       };
      });
    }

    function createMarker(latlng, name, address) {
      var html = "<b>" + name + "</b> <br/>" + address;
      var marker = new google.maps.Marker({
        map: map,
        position: latlng
      });
      google.maps.event.addListener(marker, 'click', function() {
        infoWindow.setContent(html);
        infoWindow.open(map, marker);
      });
      markers.push(marker);
    }

    function createOption(name, distance, num) {
      var option = document.createElement("option");
      option.value = num;
      option.innerHTML = name + "(" + distance.toFixed(1) + ")";
      locationSelect.appendChild(option);
    }

    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.responseText, request.status);
        }
      };

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

    function parseXml(str) {
      if (window.ActiveXObject) {
        var doc = new ActiveXObject('Microsoft.XMLDOM');
        doc.loadXML(str);
        return doc;
      } else if (window.DOMParser) {
        return (new DOMParser).parseFromString(str, 'text/xml');
      }
    }

    function doNothing() {}

    //]]>
  </script>
  </head>

  <body style="margin:0px; padding:0px;" onLoad="load()">
    <div>
     <input type="text" id="addressInput" size="10"/>
    <select id="radiusSelect">
      <option value="25" selected>25mi</option>
      <option value="100">100mi</option>
      <option value="200">200mi</option>
    </select>

    <input type="button" onClick="searchLocations()" value="Search"/>
    </div>
    <div><select id="locationSelect" style="width:100%;visibility:hidden"></select></div>
    <div id="map" style="width: 100%; height: 80%"></div>
  </body>
</html>

- AbsarAkram

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- david strachan · Accepted Answer

http://funfeat.com/clients/gmap/gmap.php?lat=47&lng=-122&radius=2 生成有效的XML，但是您的查询可能有误。它会提取出10个标记，其中9个是正确的，但第10个会产生<marker name="Pakistan" address="Chowk Azam, Layyah" lat="31.008364" lng="71.224342" type="cITY"/>，这肯定不在坐标范围内2英里之内。您的查询不应该从数据库中选取最后一个标记。

由于mysql_函数的使用不被鼓励，因此可以使用以下代码使用PDO

//dependant on your setup
$host= "WWW";
$username="XXX";
$password="YYY";
$database="ZZZ";
// Get parameters from URL
$center_lat = $_GET["lat"];
$center_lng = $_GET["lng"];
$radius = $_GET["radius"];

// Start XML file, create parent node
$dom = new DOMDocument("1.0");
$node = $dom->createElement("markers");
$parnode = $dom->appendChild($node);
//Connect to database
$dbh = new PDO("mysql:host=$host;dbname=$database", $username, $password);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
try {
    // Prepare statement
    $stmt = $dbh->prepare("SELECT  name, lat, lng, ( 3959 * acos( cos( radians(?) ) * cos( radians( lat ) ) * cos( radians( lng ) - radians(?) ) + sin( radians(?) ) * sin( radians( lat ) ) ) ) AS distance FROM gbstn HAVING distance < ? ORDER BY distance ASC LIMIT 0 , 20");
    // Assign parameters
    $stmt->bindParam(1,$center_lat);
    $stmt->bindParam(2,$center_lng);
    $stmt->bindParam(3,$center_lat);
    $stmt->bindParam(4,$radius);
    //Execute query
    $stmt->setFetchMode(PDO::FETCH_ASSOC);
    $stmt->execute();

编辑：添加了代码以捕获没有记录的错误。

    if ($stmt->rowCount()==0) {
    $node = $dom->createElement("marker");
    $newnode = $parnode->appendChild($node);
    $newnode->setAttribute("name", "No Records Found");
    $newnode->setAttribute("lat", $center_lat);//Sends marker to search location 
    $newnode->setAttribute("lng", $center_lng);
    $newnode->setAttribute("distance", 0);
            } 
   else {

EDIT结束

    // Iterate through the rows, adding XML nodes for each
    while($row = $stmt->fetch()) {
        $node = $dom->createElement("marker");
        $newnode = $parnode->appendChild($node);
        $newnode->setAttribute("name", $row['name']);
        $newnode->setAttribute("address", $row['address']);
        $newnode->setAttribute("lat", $row['lat']);
        $newnode->setAttribute("lng", $row['lng']);
        $newnode->setAttribute("distance", $row['distance']);
        }
    }
echo $dom->saveXML();

}


catch(PDOException $e) {
    echo "I'm sorry I'm afraid you can't do that.". $e->getMessage() ;// Remove or modify after testing 
    file_put_contents('PDOErrors.txt',date('[Y-m-d H:i:s]').", gmap.php, ". $e->getMessage()."\r\n", FILE_APPEND);  
 }
//Close the connection
$dbh = null;

上述查询中的 HAVING distance < '%s' 部分应该可以过滤掉最后一个标记。

如果搜索找不到任何记录并且将地图发送到纬度/经度为0,0，则我已添加错误捕获。请见此处查看我的实现。