ngx-leaflet: How to add a custom control?

Question

I have tried for a while now to implement this leaflet tutorial using the ngx-leaflet.

There is absolutely no clear documentation on how to implement a custom control or legend while following along with the tutorial.

var info = L.control();

info.onAdd = function (map) {
    this._div = L.DomUtil.create('div', 'info'); // create a div with a class "info"
    this.update();
    return this._div;
};

// method that we will use to update the control based on feature properties passed
info.update = function (props) {
    this._div.innerHTML = '<h4>US Population Density</h4>' +  (props ?
        '<b>' + props.name + '</b><br />' + props.density + ' people / mi<sup>2</sup>'
        : 'Hover over a state');
};

info.addTo(map);

Same goes for creating a legend.

Can any point me in the right direction to try and get this implemented in Angular 7 with ngx-leaflet lib?

import { control, featureGroup, geoJson, icon, latLng, LatLngExpression, Map, Marker, marker, popup, tileLayer } from 'leaflet';

  onMapReady(map: Map) {
    this.map = map;

    // create info control
    let info = control(
      {
        onAdd: map => {

        }
      }
    )
    info.addTo(map);

I get that you need to do something like this, but I don't want to add a circle or shape, but the custom control in the screenshot above as well as a legend.

Generally, you’d follow the ngx-leaflet readme to get a reference to the map. And then you can add the custom control to the map just like the tutorial does. — reblace, Feb 17 '19 at 15:14
Problem is there is no clear documentation on how to add a custom control. I've tried numerous methods but just end up with run time errors around the custom control. — Dylan, Feb 17 '19 at 15:24
You can't go let info = L.control(); for example as this does not work properly. Also not sure which imports to use. — Dylan, Feb 17 '19 at 15:47

score 6 · Accepted Answer · answered Feb 17 '19 at 16:33

The only thing you need to do to make this example work is to listen to onMapReady event & place all the code of the tutorial inside there. Map reference is what you want and it comes as an argument to this function.

Specifically:

<div
  style="height: 100vh"
  leaflet
  [leafletOptions]="options"
  (leafletMapReady)="onMapReady($event)"
></div>

ts:

onMapReady(map) {
 // place all the tutorial code inside here
 ...

// control that shows state info on hover
let info = L.control();

// here you want the reference to be info, therefore this = info
// so do not use es6 to access the the class instance
info.onAdd = function (map) {
  this._div = L.DomUtil.create('div', 'info');
  this.update();
  return this._div;
};

// also here you want the reference to be info, therefore this = info
// so do not use es6 to access the class instance
info.update = function (props) {
  this._div.innerHTML = '<h4>US Population Density</h4>' + (props ?
    '<b>' + props.name + '</b><br />' + props.density + ' people / mi<sup>2</sup>'
    : 'Hover over a state');
};

info.addTo(map);
...
const legend = L.control({ position: 'bottomright' });

legend.onAdd = map => {

  let div = L.DomUtil.create('div', 'info legend'),
    grades = [0, 10, 20, 50, 100, 200, 500, 1000],
    labels = [],
    from, to;

  for (var i = 0; i < grades.length; i++) {
    from = grades[i];
    to = grades[i + 1];

    labels.push(
      '<i style="background:' + getColor(from + 1) + '"></i> ' +
      from + (to ? '&ndash;' + to : '+'));
  }

  div.innerHTML = labels.join('<br>');
  return div;
};

legend.addTo(map);
}

Check the demo for the full example in Angular 7 using ngx-leaflet

This does work thank you. I thought there would be a more "angular" way to handle this. Also VERY important is the: import * as L from "leaflet" part. — Dylan, Feb 18 '19 at 08:12

ngx-leaflet: How to add a custom control?

1 Answers1