react-leaflet: wie Zoom basierend auf Geojson setzen

Question

Ich benutze react-leaflet und meine Karte zeigt bis jetzt gut. Ich habe auch erfolgreich <GeoJson> verwendet, um ein Polygon zu überlagern.

Momentan habe ich meine Center- und Zoom-Werte fest codiert, aber ich möchte, dass mein Standardzoom so eingestellt wird, dass das gesamte GeoJSON-Polygon sichtbar ist. Ich kämpfe mit den Unterlagen/Antworten, die ich im Internet gefunden habe (ich bin nur Anfänger/Fortgeschrittene JS).

Hier ist meine Komponente:

import React from 'react'; 
import { StyleSheet, css } from 'aphrodite/no-important'; 
import L from 'leaflet'; 
import { Map, TileLayer, Marker, Popup, GeoJson } from 'react-leaflet'; 
import axios from 'axios'; 

const styles = StyleSheet.create({ 
    map: { 
    height: 240, 
    width: '100%' 
    } 
}); 

const geodatas = { "type": "Polygon", "coordinates": [ [ [ 0.901409326032148, 51.87846074983652 ], [ 0.900728205963941, 51.87844428860128 ], [ 0.899345524616457, 51.8784325381963 ], [ 0.898758899468915, 51.878417331772674 ], [ 0.898382518544509, 51.87839424237513 ], [ 0.897325195329164, 51.878223304667991 ], [ 0.89594922021314, 51.877976588301692 ], [ 0.894955640203439, 51.877846407999037 ], [ 0.894280316390969, 51.877785709788448 ], [ 0.893320356777677, 51.877703150758911 ], [ 0.892628493048771, 51.877632959777358 ], [ 0.892139172447305, 51.877548791413972 ], [ 0.891852225577892, 51.877468544876464 ], [ 0.891748332612011, 51.877548514557468 ], [ 0.891456640213901, 51.877849701135801 ], [ 0.891291905863462, 51.878157745192553 ], [ 0.891212527716225, 51.878460992695949 ], [ 0.891079390830871, 51.879306113637384 ], [ 0.891068489722895, 51.879386403461886 ], [ 0.890532814748409, 51.879394179295069 ], [ 0.890012032842571, 51.879477202674821 ], [ 0.889375209183071, 51.879561187317655 ], [ 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[ 0.901409326032148, 51.87846074983652 ] ] ] } 

class MapHolder extends React.Component { 
    constructor() { 
    super(); 
    this.state = { 
     geodatas: geodatas, 
     lat: 51.881403, 
     lng: 0.918583, 
     zoom: 17, 
    }; 
    } 


    render() { 
const accessToken = 'pk.eyJ1IjoiZ2F6YXN0b24iLCJhIjoiY2loa21hNzRoMG50eHQ0bHp2azNpeHhwaiJ9.h81FekBCVUufbqxc9ywySQ' 
const position = [this.state.lat, this.state.lng]; 

console.log(this.refs.geojson); 
console.log(this.refs.foo.leafletElement); 

this.refs.foo.leafletElement.fitBounds(this.refs.geojson.getBounds()); 

return (
    <div> 
    <Map ref="foo" style={{height: "260px"}} center={position} zoom={this.state.zoom} scrollWheelZoom={false} > 
    <TileLayer 
     attribution='&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors' 
     url={`https://api.mapbox.com/styles/v1/gazaston/cihkojpjh00whrom498ghjoc5/tiles/256/{z}/{x}/{y}?access_token=${accessToken}`} 
     id='gazaston.o9phia6g' 
     detectRetina={true} 
    /> 
    <GeoJson ref="geojson" data={this.state.geodatas} /> 
    </Map> 
    </div> 
); 

} 

export default MapHolder; 

UPDATE:

Wenn ich die Entwickler-Tools Reagieren verwenden, wählen Sie meine <MapHolder> Komponente, wechseln auf die Konsole, und führen

$r.refs.foo.leafletElement.fitBounds($r.refs.geojson.leafletElement.getBounds());

alles funktioniert wie erwartet. Doch in meinem Code

this.refs.foo.leafletElement.fitBounds(this.refs.geojson.leafletElement.getBounds());

kehrt Uncaught TypeError: Cannot read property 'leafletElement' of undefined

Ich bin so nah! Was vermisse ich?

Answer 1

Basierend auf @IvanSanchez Antwort und wie reagieren-Faltblatt Arbeiten würde ich

<GeoJson ref="geojson" data={this.state.geodatas} /> 

dann Zugriff auf die Karte mit ref

this.refs.foo.leafletElement.fitBounds(this.refs.geojson.leafletElement.getBounds()) 

Answer 2

Wegen der eine ref auf Ihre GeoJSON Schicht zuerst hinzufügen vorschlagen So wie das reactive-leaflet seine lifecycle handhabt, in der es die Kontrolle auf das Flugblatt umkehrt, sobald es die Map-Komponente mountet, kann es schwierig sein, auf Unterkomponentenreferenzen zuzugreifen.

Ich löste dieses Problem auf zwei Arten.

Mein erster Versuch beinhaltete das Speichern der Anzahl von Features, die innerhalb meines äußeren Komponentenstatus hinzugefügt wurden, Anfügen eines map-object Ereignishandlers für layeradd, wie oben empfohlen, und dann Zugreifen auf die Geojson ref, sobald alle Polygone hinzugefügt wurden.

`` `

componentDidMount() { 
    let count = 0; 
    const map = this.refs.map.leafletElement; 
    map.on('layeradd',() => { 
     count += 1; 
     if (count > this.state.polygonCount) { 
      setTimeout(()=>{DO STUFF}, 200) 
     } 
    }); 
} 

` ``

Das funktioniert zwar, es riecht.

Die zweite Möglichkeit, die ich gelöst habe, war, turf-bbox zu verwenden, um die Grenzen des Geojons vorzurechnen, die ich dann in meiner Rendermethode an das Map-Objekt übergeben habe.

`` `

const bboxArray = bbox(geojson); 
const corner1 = [bboxArray[1], bboxArray[0]]; 
const corner2 = [bboxArray[3], bboxArray[2]]; 
this.state.bounds = [corner1, corner2]; 

` ``

und dann

`` `

<Map bounds={this.state.bounds} ref="map"> 

` ``

Der zweite Weg ist viel sauberer wenn du keine brauchst etwas mehr mit dem GeoJSON leafletElement, aber die erste Möglichkeit lässt Sie eine beliebige Anzahl von Event-Handlern einrichten, usw.