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<script>
// holds an instance of XMLHttpRequest
var xmlHttp = createXmlHttpRequestObject();
// creates an XMLHttpRequest instance
function createXmlHttpRequestObject()
{
// will store the reference to the XMLHttpRequest object
var xmlHttp;
// this should work for all browsers except IE6 and older
try
{
// try to create XMLHttpRequest object
xmlHttp = new XMLHttpRequest();
}
catch(e)
{
// assume IE6 or older
var XmlHttpVersions = new Array("MSXML2.XMLHTTP.6.0",
"MSXML2.XMLHTTP.5.0",
"MSXML2.XMLHTTP.4.0",
"MSXML2.XMLHTTP.3.0",
"MSXML2.XMLHTTP",
"Microsoft.XMLHTTP");
// try every prog id until one works
for (var i=0; i<XmlHttpVersions.length && !xmlHttp; i++)
{
try
{
// try to create XMLHttpRequest object
xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
}
catch (e) {}
}
}
// return the created object or display an error message
if (!xmlHttp)
<?fwrite($log,"Error creating the XMLHttpRequest object.")?>;
else
return xmlHttp;
}
// read a file from the server
function process()
{
// only continue if xmlHttp isn't void
if (xmlHttp)
{
// try to connect to the server
try
{
// initiate reading a file from the server
xmlHttp.open("GET", "update.php?id=".$_GET['id']."", true);
xmlHttp.onreadystatechange = handleRequestStateChange;
xmlHttp.send(null);
}
// display the error in case of failure
catch (e)
{
<? fwrite($log,"Can't connect to server:\n")?>;
}
}
}
// function called when the state of the HTTP request changes
function handleRequestStateChange()
{
// when readyState is 4, we are ready to read the server response
if (xmlHttp.readyState == 4)
{
// continue only if HTTP status is "OK"
if (xmlHttp.status == 200)
{
try
{
// do something with the response from the server
handleServerResponses();
}
catch(e)
{
// display error message
<? fwrite($log,"Error reading the response: ");?>
}
}
else
{
// display status message
<? fwrite($log,"There was a problem retrieving the data:\n");?>
}
}
}
// handles the response received from the server
function handleServerResponses()
{
// read the message from the server
var xmlResponse = xmlHttp.responseXML;
// catching potential errors with IE and Opera
if (!xmlResponse || !xmlResponse.documentElement)
throw("Invalid XML structure:\n" + xmlHttp.responseText);
// catching potential errors with Firefox
var rootNodeName = xmlResponse.documentElement.nodeName;
if (rootNodeName == "parsererror") throw("Invalid XML structure");
// obtain the XML's document element
xmlRoot = xmlResponse.documentElement;
// obtain arrays with book titles and ISBNs
titleArray = xmlRoot.getElementsByTagName("title");
isbnArray = xmlRoot.getElementsByTagName("isbn");
// generate HTML output
// iterate through the arrays and create an HTML structure
latc = titleArray.item(0).firstChild.data;
lonc = isbnArray.item(0).firstChild.data;
lonc = parseFloat(lonc);
latc = parseFloat(latc);
setInterval('process()',17000);
var lonLat1 = new OpenLayers.LonLat(lonc,latc)
.transform(new OpenLayers.Projection("EPSG:4326"), // преобразование из WGS 1984
new OpenLayers.Projection("EPSG:900913")
);
map.setCenter(lonLat1, 16);
var icon = new OpenLayers.Icon('images/car.png', size, offset);
var size = new OpenLayers.Size(21,25);
var offset = new OpenLayers.Pixel(-(size.w/2), -size.h);
marker2 = new OpenLayers.Layer.Markers("Car");
map.addLayer(marker2);
marker2.addMarker(new OpenLayers.Marker(lonLat1,icon));
}
function init()
{
map = new OpenLayers.Map("basicMap");
var mapnik = new OpenLayers.Layer.OSM();
map.addLayer(mapnik);
lat = <? //echo $lat ?>;
lon = <? //echo $lon ?>;
var lonLat = new OpenLayers.LonLat(lon,lat)
.transform(new OpenLayers.Projection("EPSG:4326"), // преобразование из WGS 1984
new OpenLayers.Projection("EPSG:900913")
);
marker = new OpenLayers.Layer.Markers("Marker");
map.addLayer(marker);
var size = new OpenLayers.Size(21,25);
var offset = new OpenLayers.Pixel(-(size.w/2), -size.h);
var icon = new OpenLayers.Icon('images/marker-def.png', size, offset);
marker.addMarker(new OpenLayers.Marker(lonLat,icon.clone()));
}
</script>
</head>
<body onload="process(); init()">
如何在更新新標記2後刪除以前的標記2？如何刪除以前的標記？