嘗試使用 react-leaflet-choropleth map choropleth 時出錯：無法讀取未定義的屬性“地圖”

Question

我正在嘗試使用react react-leaflet-choropleth 。

我的 leaflet 工作正常。
現在，當我嘗試使用庫加載geojson （crimes_by_district）時，在映射功能時遇到錯誤，特別是：

Cannot read property 'map' of undefined

看來我沒有准確地將正確的數組引用到 map。

我查看了 git 存儲庫中的問題並嘗試了這些建議，但沒有成功。 我想知道我是否從我正在使用的geoJson中引用了不正確的值。

下面是我的代碼：

Leaf.js （在 App.js 中渲染）

import React, { Component } from 'react';
import { Map, TileLayer } from 'react-leaflet';
import classes from './leaf.module.css'
import Choropleth from 'react-leaflet-choropleth'
import geojson from "./assets/crimes_by_district.geojson";
    
const style = {
   fillColor: '#F28F3B',
   weight: 2,
   opacity: 1,
   color: 'white',
   dashArray: '3',
   fillOpacity: 0.5
};
    
class Leaf extends Component {
   render() { 
      return (         
         <Map>
           <Choropleth
             data= {{type: 'FeatureCollection', features: geojson.features}}
             valueProperty={(feature) => feature.properties.value}
             // visible={(feature) => feature.id !== active.id}
             scale={['#b3cde0', '#011f4b']}
             steps={7}
             mode='e'
             style={style}
             onEachFeature={
               (feature, layer) => layer.bindPopup(feature.properties.label)
             }
             ref={(el) => this.choropleth = el.leafletElement}
           />
         </Map>
      );
   }
}
    
export default Leaf;

Answer 1

使用與您包含的擴展類似的相同 choropleth 庫創建您自己的choropleth wrapper ，因為react-leaflet-choropleth似乎已過時：

function Choropleth() {
  const { map } = useLeaflet();

  useEffect(() => {
    fetch(
      "https://raw.githubusercontent.com/timwis/leaflet-choropleth/gh-pages/examples/basic/crimes_by_district.geojson"
    )
      .then((response) => response.json())
      .then((geojson) => {
        L.choropleth(geojson, {
          valueProperty: "incidents", // which property in the features to use
          scale: ["white", "red"], // chroma.js scale - include as many as you like
          steps: 5, // number of breaks or steps in range
          mode: "q", // q for quantile, e for equidistant, k for k-means
          style,
          onEachFeature: function (feature, layer) {
            layer.bindPopup(
              "District " +
                feature.properties.dist_num +
                "<br>" +
                feature.properties.incidents.toLocaleString() +
                " incidents"
            );
          }
        }).addTo(map);
      });
  }, []);

  return null;
}

然后將其作為 Map 子項導入：

<Map center={position} zoom={11} style={{ height: "100vh" }}>
        <TileLayer
          attribution='&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
          url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
        />
   <Choropleth />
</Map>

您可以通過傳遞所需的各種變量作為道具來進一步擴展它。

演示