出身背景

我在一个网站上工作,我有父组件和子组件。下面的代码片段是一个谷歌地图包装器和一个地图组件。

密码

import React, { useEffect, useState, useRef } from "react";

// reactstrap components
import { Card, Container, Row } from "reactstrap";

// core components
import Header from "components/Headers/Header.js";
import LocationSearchInput from "../../components/Places";
import { useAuthenticator } from "@aws-amplify/ui-react";
import * as queries from "../../graphql/queries";
import { API, graphqlOperation } from "aws-amplify";
import { geocodeByAddress, getLatLng } from "react-places-autocomplete";
import * as _ from "lodash";
import { collapseTextChangeRangesAcrossMultipleVersions } from "typescript";

const ChildComponent = (data, loc) => {
  const mapRef = useRef(null);
  console.log("child props", data, loc);

  console.log("foo child", loc);
  // THIS WONT WORK BECAUSE WHEN IT FIRST LOADS ITS EMPTY
  // geocodeByAddress(loc[0].HomeLocation)
  //     .then(results => getLatLng(results[0]))
  //     .then(latLng => console.log('Success', latLng))
  //     .catch(error => console.error('Error', error))

  useEffect(() => {
console.log("child mount");
    let google = window.google;
    let map = mapRef.current;
    let lat = "40.748817";
    let lng = "-73.985428";
    const myLatlng = new google.maps.LatLng(lat, lng);
    const mapOptions = {
      zoom: 12,
      center: myLatlng,
      scrollwheel: false,
      zoomControl: true,
      styles: [
        {
          featureType: "administrative",
          elementType: "labels.text.fill",
          stylers: [{ color: "#444444" }],
        },
        {
          featureType: "landscape",
          elementType: "all",
          stylers: [{ color: "#f2f2f2" }],
        },
        {
          featureType: "poi",
          elementType: "all",
          stylers: [{ visibility: "off" }],
        },
        {
          featureType: "road",
          elementType: "all",
          stylers: [{ saturation: -100 }, { lightness: 45 }],
        },
        {
          featureType: "road.highway",
          elementType: "all",
          stylers: [{ visibility: "simplified" }],
        },
        {
          featureType: "road.arterial",
          elementType: "labels.icon",
          stylers: [{ visibility: "off" }],
        },
        {
          featureType: "transit",
          elementType: "all",
          stylers: [{ visibility: "off" }],
        },
        {
          featureType: "water",
          elementType: "all",
          stylers: [{ color: "#5e72e4" }, { visibility: "on" }],
        },
      ],
    };

    map = new google.maps.Map(map, mapOptions);

    const marker = new google.maps.Marker({
      position: myLatlng,
      map: map,
      animation: google.maps.Animation.DROP,
      title: "Light Bootstrap Dashboard PRO React!",
    });

    const contentString =
      '<div class="info-window-content"><h2>Light Bootstrap Dashboard PRO React</h2>' +
      "<p>A premium Admin for React-Bootstrap, Bootstrap, React, and React Hooks.</p></div>";

    const infowindow = new google.maps.InfoWindow({
      content: contentString,
    });

    google.maps.event.addListener(marker, "click", function () {
      infowindow.open(map, marker);
    });
  }, []);

  console.log("child render");
  return (
    <>
      <div
        style={{ height: `600px` }}
        className="map-canvas"
        id="map-canvas"
        ref={mapRef}
      ></div>
    </>
  );
};



//PARENT COMPONENT
const Parent = () => {
  const [foo, setFoo] = useState([]);

  const { user, signOut } = useAuthenticator((context) => [context.user]);
  // console.log("user map", user);

  const [pin, setPin] = useState([]);

  const fetchFoo = async () => {
    console.log(user.attributes.email);
    try {
      const todoData = API.graphql(
        graphqlOperation(queries.listEmployees, {
          filter: {
            Email: {
              eq: user.attributes.email,
            },
          },
        })
      ).then((response) => {
          console.log("fetch resp", response);
          setFoo(response.data.listEmployees.items);
        })
        .catch((err) => {
          console.log(err);
        });
    } catch (err) {
      console.log("error facing Todos:", err);
    }
  };
  console.log("parent render");

  useEffect(() => {
    console.log("parent mount")
    fetchFoo();
  }, []);

  var json = [{a: "a", b:"b"}]

  return (
    <>
      <Header />
      {/* Page content */}
      {/* {foo} */}
      <Container className="mt--7" fluid>
        <Row>
          <div className="col">
            {/* <LocationSearchInput /> */}
          </div>
        </Row>
        <Row>
          <div className="col">
            <Card className="shadow border-0">
              {/* <> */}
              <ChildComponent data={json} loc={{foo}}/>
              {/* </> */}
            </Card>
          </div>
        </Row>
      </Container>
    </>
  );
};

export default Parent;

输出

问题

子组件首次读取数据时为空,但在第二次加载时填充。我已经尝试过调整useEffect以使其工作,但唯一的区别是,如果移除空数组,它将执行无限循环。