Dynamic google map markers via simple jSon file

After making my previous post on how to simply store comments in a jSon file (and the comment from Brian) I decided to write an additional HOWTO create dynamic markers and store them in a jSon file.

It also includes an automatic geo data lockup via Google GeoCoder and generates a detail html file for-each marker created, which then will be loaded dynamic when the marker is clicked.

Check out the working example or download the code on GitHub.

GitHub

So lets get started with the code.

First we need to add jQuery and the Google map API:

The HTML code is very basic and contains a Title, Input field for new markers and the placeholder for the map. Make sure to add “loadMap()” to the html body.

So lets have a look at the JavaScript, first we set some global variables like data path zoom level etc:

// data file with markers (could also be a PHP file for dynamic markers)
var newDate = new Date;
var markerFile = 'markers.json?time=' + newDate.getTime();

// set default map properties
var defaultLatlng = new google.maps.LatLng(49.00,10.00);

// zoom level of the map
var defaultZoom = 2;

// variable for map
var map;

// variable for marker info window
var infowindow

// List with all marker to check if exist
var markerList = {};

// set error handler for jQuery AJAX requests
$.ajaxSetup({"error":function(XMLHttpRequest,textStatus, errorThrown) 
	alert(textStatus);
	alert(errorThrown);
	alert(XMLHttpRequest.responseText);
}});

// option for google map object
var myOptions = {
	zoom: defaultZoom,
	center: defaultLatlng,
	mapTypeId: google.maps.MapTypeId.HYBRID
}

On page load loadMap is fired which which loads the google map to the myMapDIV, and then fires loadMarkers:

/**
 * Load Map
 */
function loadMap(){

	// create new map make sure a DIV with id myMap exist on page
	map = new google.maps.Map(document.getElementById("myMap"), myOptions);

	// create new info window for marker detail pop-up
	infowindow = new google.maps.InfoWindow();

	// load markers
	loadMarkers();
}

Now we need the markers, loadMarkers loads the existing markers via ajax request directly from the data.json fiel (could of course also be a dynamic PHP files which generates jSon).

/**
 * Load markers via ajax request from server
 */
function loadMarkers(){

	// load marker jSon data
	$.getJSON(markerFile, function(data) {

		// loop all the markers
		$.each(data.markers, function(i,item){

			// add marker to map
			loadMarker(item);
		});
	});
}

Once the markers are loaded they somehow have to go on the map:

/**
 * Load marker to map
 */
function loadMarker(markerData){

	// create new marker location
	var myLatlng = new google.maps.LatLng(markerData['lat'],markerData['long']);

	// create new marker
	var marker = new google.maps.Marker({
	    id: markerData['id'],
	    map: map,
	    title: markerData['name'] ,
	    position: myLatlng
	});

	// add marker to list used later to get content and additional marker information
	markerList[marker.id] = marker;

	// add event listener when marker is clicked
	// currently the marker data contain a dataurl field this can of course be done different
	google.maps.event.addListener(marker, 'click', function() {

		// show marker when clicked
		showMarker(marker.id);
	});

	// add event when marker window is closed to reset map location
	google.maps.event.addListener(infowindow,'closeclick', function() {
		map.setCenter(defaultLatlng);
		map.setZoom(defaultZoom);
	});
}

Each marker has an onclick event which loads the detail marker html file into a google infowindow.

/**
 * Show marker info window
 */
function showMarker(markerId){

	// get marker information from marker list
	var marker = markerList[markerId];

	// check if marker was found
	if( marker ){

		// get marker detail information from server
		$.get( 'data/' + marker.id + '.html' , function(data) 

			// show marker window
			infowindow.setContent(data);
			infowindow.open(map,marker);
		});
	}else{
		alert('Error marker not found: ' + markerId);
	}
}

Here the logic for lockup new markers and post them via AJAX jSon request to the server.

 /**
 * Adds new marker to list
 */

function newMarker(){

	// get new city name
	var markerAddress = $('#newMarker').val();

	// create new geocoder for dynamic map lookup
	var geocoder = new google.maps.Geocoder();

	geocoder.geocode( { 'address': markerAddress}, function(results, status) {

		// check response status
		if (status == google.maps.GeocoderStatus.OK) {

			// Fire Google Goal
			_gaq.push(['_trackPageview', '/tracking/marker-submit']);

			// set new maker id via timestamp
			var newDate = new Date;
			var markerId = newDate.getTime();

			// get name of creator
			var markerCreator = prompt("Please enter your name","");

			// create new marker data object
			var markerData = {
				'id': markerId,
				'lat': results[0].geometry.location.lat(),
				'long': results[0].geometry.location.lng(),
				'creator': markerCreator,
				'name': markerAddress,
			};

			// save new marker request to server
			$.ajax({
				type: 'POST',
				url: "data.php",
				data: {
					marker: markerData
				},

				dataType: 'json',
				async: false,
				success: function(result){

					// add marker to map
					loadMarker(result);

					// show marker detail
					showMarker(result['id']);
				}
			});
		}else if( status == google.maps.GeocoderStatus.OVER_QUERY_LIMIT){
			alert("Marker not found:" + status);
		}
	});
}

The PHP code to save the marker is pretty much the same as in my previous post, and returns the newly create marker data:

/* get markes from file */
$dataPath = '/var/www/gmap/data/';
$markerDataFile = 'markers.json';
$markerText = file_get_contents($markerDataFile);

/* create array list from markers */
$markerList = json_decode($markerText,true);

/* check if new marker is posted */
if( !empty($_POST['marker'])  ){

	/* get new marker data */
	$markerData =  $_POST['marker'];

	/* add additional marker information */
	$markerData['ip'] = $_SERVER['REMOTE_ADDR'];
	$markerData['created'] = time();

	/*  create detail marker content file */
	$markerContent = $markerData['creator'] . "-> " . $markerData['name'];

	$markerContent .= date("D M j G:i:s T Y");

	/* save marker file to server */
	$markerFile = $dataPath . $markerData['id'] . ".html";
	file_put_contents($markerFile  , $markerContent);

        /* add new marker to existing list */
        $markerList['markers'][] = $markerData;

        /* convert comments to string */
        $markerText = json_encode($markerList);

        /* save comment to file */
        file_put_contents($markerDataFile, $markerText);

        /* return newly created marker */
	echo json_encode($markerData);
}else{
	echo "Invalid request";
}

This should give a good start on how to dynamically add and display markers via Google map.

The code

Check out the working example or download the code on GitHub.

GitHub