反应叶，打开/关闭弹出窗口时标记会重新渲染

Question

问题是，每次我将鼠标悬停在一个标记上时，都会打开或关闭一个弹出窗口，即使我的状态没有改变，也会导致所有标记重新渲染。每当我将鼠标悬停在标记上时，console.log(myState);就会运行。

我尝试使用useMemo挂钩，但无法弄清楚如何在country.map上使用它。有帮助吗？

这是我的代码：

import React, { useEffect, useState } from 'react';
import { Map, TileLayer, Marker, Popup } from 'react-leaflet';
import axios from 'axios';
import { v4 as uuidv4 } from 'uuid';
import { Icon } from 'leaflet';

const myicon = new Icon({
  iconUrl: './icon.svg',
  iconSize: [20, 20]
});

const MyMap = () => {
  const [myState, setMyState] = useState(null);
  const [activePlace, setActivePlace] = useState(null);

  const getData = async () => {
    let response = await axios
      .get('https://corona.lmao.ninja/v2/jhucsse')
      .catch(err => console.log(err));

    let data = response.data;
    setMyState(data);

    // console.log(data);
  };

  useEffect(() => {
    getData();
  }, []);

  if (myState) {
    console.log(myState);
    return (
        <Map
          style={{ height: '100vh', width: '100vw' }}
          center={[14.561, 17.102]}
          zoom={1}
        >
          <TileLayer
            attribution='&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors &copy; <a href="https://carto.com/attributions">CARTO</a>'
            url={
              'https://{s}.basemaps.cartocdn.com/dark_all/{z}/{x}/{y}{r}.png'
            }
          />

          {myState.map(country => {
            return (
              <Marker
                key={uuidv4()}
                position={[
                  country.coordinates.latitude,
                  country.coordinates.longitude
                ]}
                onmouseover={() => {
                  setActivePlace(country);
                }}
                onmouseout={() => {
                  setActivePlace(null);
                }}
                icon={myicon}
              />
            );
          })}

          {activePlace && (
            <Popup
              position={[
                activePlace.coordinates.latitude,
                activePlace.coordinates.longitude
              ]}
            >
              <div>
                <h4>Country: {activePlace.country}</h4>
              </div>
            </Popup>
          )}
        </Map>
    );
  } else {
    return <div>Nothing</div>;
  }
};

export default MyMap;

Answer 1

尝试一下：

onmouseover={() => {
  setActivePlace({...country});
}}

country调用中的map()指向myState中的同一对象引用，因此，当您更新一个对象时，您将同时更新两个对象。如果您破坏country对象的结构，您将复制一个副本以传递到setActivePlace，并且它不会指向相同的引用。