How do I get the latlng after the dragend event in leaflet? - event-handling

I'm trying to update the lat/lng value of a marker after it is moved. The example provided uses a popup window to display the lat/lng.
I have a "dragend" event listener for the marker, but when I alert the value of e.latlng it returns undefined.
javascript:
function markerDrag(e){
alert("You dragged to: " + e.latlng);
}
function initialize() {
// Initialize the map
var map = L.map('map').setView([38.487, -75.641], 8);
L.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
attribution: 'Map data © OpenStreetMap contributors, CC-BY-SA',
maxZoom: 18
}).addTo(map);
// Event Handlers
map.on('click', function(e){
var marker = new L.Marker(e.latlng, {draggable:true});
marker.bindPopup("<strong>"+e.latlng+"</strong>").addTo(map);
marker.on('dragend', markerDrag);
});
}
$(document).ready(initialize());
http://jsfiddle.net/rhewitt/Msrpq/4/

Use e.target.getLatLng() to get the latlng of the updated position.
// Script for adding marker on map click
function onMapClick(e) {
var marker = L.marker(e.latlng, {
draggable:true,
title:"Resource location",
alt:"Resource Location",
riseOnHover:true
}).addTo(map)
.bindPopup(e.latlng.toString()).openPopup();
// #12 : Update marker popup content on changing it's position
marker.on("dragend",function(e){
var chagedPos = e.target.getLatLng();
this.bindPopup(chagedPos.toString()).openPopup();
});
}
JSFiddle demo

latlng value is not in e.latlng but in e.target._latlng .
Use console.

While using e.target._latlng works (as proposed by this other answer), it's better practice to use
e.target.getLatLng();
That way we're not exposing any private variables, as is recommended by Leaflet:
Private properties and methods start with an underscore (_). This doesn’t make them private, just recommends developers not to use them directly.

I think the API changed.
Nowadays is: const { lat, lng } = e.target.getCenter();

if anyone is using react than you should use :
const map = useMap()
map.addEventListener("dragend" , ()=> {
const {lat , lng} = map.getCenter()
})

Related

Leaflet current position multiple markers

Hello everyone I have some problems its about the current positionmarker in my leaflet its supposed to update every 3 second and it does but it everytime it puts a new "position" marker on the map and the old one stays how can i fix this?
L.tileLayer('https://api.mapbox.com/styles/v1/{id}/tiles/{z}/{x}/{y}?access_token={accessToken}', {
attribution: '© Leaflet 2021',
tileSize: 512,
zoomOffset: -1,
id: 'mapbox/streets-v11',
accessToken: '######'
}).addTo(map);
var greenIcon = L.icon({
iconUrl: 'person.png',
iconSize: [35, 35], // size of the icon // the same for the shadow
popupAnchor: [0, -20] // point from which the popup should open relative to the iconAnchor
});
// placeholders for the L.marker and L.circle representing user's current position and accuracy
var current_position, current_accuracy;
function onLocationFound(e) {
var radius = e.accuracy / 2;
var marker;
L.marker(e.latlng, {icon: greenIcon}).addTo(map)
}
// wrap map.locate in a function
function locate() {
map.locate({setView: true, maxZoom: 15});
}
map.on('locationfound', onLocationFound);
// call locate every 3 seconds... forever
setInterval(locate, 3000);
An efficient way to fix this is to keep a reference to the marker you create, so that you can update its position rather than creating a new marker each time you get a location update. The reference needs to be held in a variable that is outside your callback function, but in scope when the callback is created.
For instance, your callback can check whether the marker already exists, and either create it and attach it to the map object for easy re-use, or just update its coordinates if it is already there:
function onLocationFound(e) {
var radius = e.accuracy / 2;
if (map._here_marker) {
// Update the marker if it already exists.
map._here_marker.setLatLng(e.latlng);
} else {
// Create a new marker and add it to the map
map._here_marker = L.marker(e.latlng, {icon: greenIcon}).addTo(map);
}
}
Having this reference will also let you edit the marker from other functions, e.g. to change the icon or popup, hide it from view, etc.
You can do it, for example, in the following way.
Add an ID (customId) to the marker:
const marker = L.marker([lng, lat], {
id: customId
});
And when you add a new marker remove the existing one with the code below:
map.eachLayer(function(layer) {
if (layer.options && layer.options.pane === "markerPane") {
if (layer.options.id !== customId) {
map.removeLayer(layer);
}
}
});

Defining Leaflet map as dynamic map id (Cannot read property '_container' of undefined)

I have 2 different divs which using by leaflet as map object. I want to define my map objects into a function such as
html
<div id="mymap"></div>
<div id="mymap2"></div>
javascript
var map;
function define_map(map_id) {
var osmUrl = 'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',
osm = L.tileLayer(osmUrl, {
maxZoom: 7
}),
map = new L.Map(map_id, {
center: new L.LatLng(51.505, -0.04),
zoom: 7
}),
drawnItems = L.featureGroup().addTo(map);
});
define_map("mymap");
define_map("mymap2");
$(".btnmarker").on("click", function() {
console.log(map);
L.DomUtil.addClass(map._container, 'my_crosshair-cursor-enabled'); // ON THIS LINE GETTING ERROR CODE Cannot read property '_container' of undefined
selected_tool = $(this).attr("id");
});
There is no problem, my maps seems working good until accessing features of them from button click event (this button will add a marker class to a map which i clicked on it)
But i'm getting map is not defined error. map is a variable and defined on top line of page.
Thanks inadvance

Icon url in mapbox

How to add a custom icon in mapbox?
var map = L.mapbox.map('map', 'mapbox.streets').setView([0, 0], 1);
var geojson = { type: 'LineString', coordinates: value};
var start = value[0];
var end = value[value.length-1];
geojson.coordinates.push((start,end).slice());
// Add this generated geojson object to the map.
L.geoJson(geojson).addTo(map);
// Create a marker and add it to the map.
var marker = L.marker(end, {
icon: L.mapbox.marker.icon({
"iconUrl": "https://www.mapbox.com/mapbox.js/assets/images/astronaut2.png"
})
}).addTo(map);
});
I can't able to add a custom icon in above code. Please help me..
Thanks.
First you will have to create a var, for example 'myIcon', then simply replace the iconUrl with a path that specifies the custom marker you want to use.
You can use the iconSize option to specify the size of your marker
You can use the iconAnchor option to specify which part of your masker should be placed on the latlng.
myIcon=L.icon({
iconUrl:'img/custom-marker.png',
iconSize: [25,30]
});
Then create the marker, set the lat lng where you want your marker to be placed. And specify the icon you want to use.
var Marker = new L.Marker ( latlng, {icon:myIcon});
Finally add your market to the map:
map.addlayer(Marker);

How to get all markers on Leaflet

I have a listener that will detect changes of the location of objects on databases. It will pass all the information of the object that is being changed.
I want to get all markers from the current map and find the marker that is affected. Once found, update the location.
But, I am still looking for the best ways to get all markers from the map and then I can update the location.
var map = L.map('map').setView([37.78541,-122.40787], 13);
var markers = new L.FeatureGroup();
var mapLink =
'OpenStreetMap';
L.tileLayer(
'https://{s}.tiles.mapbox.com/v4/examples.map-i87786ca/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoiZ2Vja29iIiwiYSI6IndzVjRGN0kifQ.lToORsjE0lkt-VQ2SXOb-Q', {
attribution: '© ' + mapLink + ' Contributors',
maxZoom: 18,
}).addTo(map);
var marker = createCircleMarker([44.977368, -93.232659]);
marker._id = "69"; // Id of the marker
map.addLayer(marker);
var socket = io();
socket.on('update location', function(obj) {
// Get all markers and find markers with attribute obj.name to
// update the location to [obj.lat,obj.lon]
});
Use eachLayer method on L.map. Like
map.eachLayer(function (layer) {
if (layer.options.name === 'XXXXX') {
layer.setLatLng([newLat,newLon])
}
});
Documentation at http://leafletjs.com/reference-1.2.0.html#map-eachlayer
To add an option without using map.eachLayer; all layers within the map are internally stored in map._layers.
Use
map._layers.forEach(function (layer) {
...
});
to iterate over ALL Layer elements. Not just the ones currently visible.

Mapbox Filter Markers loaded via json

I am looking for solution to add filter (not checkbox) to my site. I have this code loading blank map from Mapbox and added Markers from JSON file. I was trying to add setFilter function, but probably I am using it wrong. I would like to filter items by category property from my JSON file.
<script>
L.mapbox.accessToken = '*************';
var baseLayer = L.mapbox.tileLayer('test****');
var markers = L.markerClusterGroup();
// CALL THE GEOJSON HERE
jQuery.getJSON("locations.geojson", function(data) {
var geojson = L.geoJson(data, {
onEachFeature: function (feature, layer) {
// USE A CUSTOM MARKER
layer.setIcon(L.mapbox.marker.icon({'marker-symbol': 'circle-stroked', 'marker-color': '004E90'}));
// ADD A POPUP
layer.bindPopup("<h1>" + feature.properties.title + "</h1><p>" + feature.properties.description + "</p><p><a href=' + feature.properties.website + '>" + feature.properties.website + "</a></p>");
layer.on('mouseover', function (e) {
this.openPopup();
});
layer.on('mouseout', function (e) {
this.closePopup();
});
}
});
markers.addLayer(geojson);
// CONSTRUCT THE MAP
var map = L.map('map', {
searchControl: {layer: markers},
zoom: 6,
center: [51.505, -0.09],
maxZoom: 13
})
.setView([62.965, 19.929], 5)
.fitBounds(markers.getBounds());
baseLayer.addTo(map);
markers.addTo(map);
L.control.fullscreen().addTo(map);
});
</script>
Could you please help me add filter buttons (something like here: https://www.mapbox.com/mapbox.js/example/v1.0.0/filtering-markers)
PS: I think I tried all examples from Mapbox website, yet seems my skills are very limited here.
Thank you
I was trying to add setFilter function, but probably I am using it wrong. I would like to filter items by category property from my JSON file.
This code example is using L.geoJson to load the markers into your map. Like the Mapbox example, you'll need to use L.mapbox.featureLayer instead, since it includes the setFilter function and L.geoJson does not.
tmcw's answer is correct, L.mapbox.featureLayer is confusing
this tutorial helped me!
https://www.mapbox.com/mapbox.js/example/v1.0.0/custom-marker-tooltip/