javascript – Google Maps V3:定期更新标记
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我已经按照谷歌地图上的PHP / MYSQL教程找到了here.
我希望每隔5秒左右从数据库中更新标记.
这是我的理解我需要使用Ajax周期性更新标记,但我很难理解在哪里添加函数以及在哪里使用setTimeout()等
我发现的所有其他例子并没有真正解释发生了什么,一些有用的指导将是非常棒的!
这是我的代码(与Google示例相同,有一些var更改):
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() {}
我希望有人可以帮助我!
解决方法:
请注意我没有测试过这个,因为我没有带xml的数据库
首先,您需要将load()函数拆分为初始化地图和函数的函数.在domready上加载标记,以及稍后用于处理xml&用地图更新地图.这需要完成,因此您不必在每次加载时重新初始化地图.
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,您可以选择重绘标记(重建阵列)或只更新现有阵列.我的示例显示了您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);
}
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