Leaflet: Map container not found

问题:

I have the below react class which fetches the geolocation through the browser.

I am mapping a leaflet map. I want to geolocation to be an input to the setView, for such that the map "zooms" into the region of the client browser location.

Here's the react class:

    import React from 'react';
    import L from 'leaflet';
    import countries from './countries.js'; 

    var Worldmap = React.createClass({

        render: function() {

            let geolocation = [];

            navigator.geolocation.getCurrentPosition(function(position) {
                let lat = position.coords.latitude;
                let lon = position.coords.longitude;
                geolocation.push(lat, lon);
                locationCode()
            });

            function locationCode() {
                if(geolocation.length <= 0)
                    geolocation.push(0, 0);
            }


            let map = L.map('leafletmap').setView(geolocation, 3);

            L.geoJSON(countries, {
                style: function(feature) {
                    return {
                        fillColor: "#FFBB78",
                        fillOpacity: 0.6,
                        stroke: true,
                        color: "black",
                        weight: 2
                    };
                }
            }).bindPopup(function(layer) {
                return layer.feature.properties.name;
            }).addTo(map);

            return (
                <div id="leafletmap" style={{width: "100%", height: "800px" }}/>
            )
        }
    });

    export default Worldmap

It's called in a main file where the HTML is rendered as <WorldMap />.

I get the error Uncaught Error: Map container not found. when loading the page. Looking around, usually it would be because the map is trying to be displayed in a div before being provided values((gelocation, 3) in this case). However, it shouldn't display it before being returned from the render function below.

What could the issue be?

Printing out the geolocation in the console correctly fetches the coordinates, so that doesn't seem to be the issue.

回答1:

The <div id="leafletmap"> must be added to the dom before calling L.map('leafletmap').

回答2:

In addition to @IvanSanchez's response, You could add the geolocation and L.map(...) code to componentDidMount() React lifecycle method (depending on what other goals you hope to achieve). You could also create and bind event handlers for location found as well.

This way must have been added the dom and leaflet can find it.

Happy to help with this if it's still unclear.