如何在继续之前等待获取 Firebase 数据?

How to wait for Firebase data to be fetched before progressing?(如何在继续之前等待获取 Firebase 数据?)

问题描述

我正在使用 .onSnapshot 从 Fire 存储中实时获取数据，效果很好，我正在按预期接收数据.问题是我正在接收多组数据，组件并没有等到接收到所有数据才渲染.

I am fetching data from Fire store in real-time with .onSnapshot and it works great, I am receiving the data as expected. The problem is that I am receiving multiple sets of data, and the component does not wait until all the data is received before rendering.

所以我的问题是，对于我当前的代码，它们是否可以让我在显示它们之前等待获取所有数据集?

So my question is, with my current code, is their a way in which I can wait for all sets of my data to be fetched before displaying them?

我当前的代码是:

import React, {useEffect, useState} from 'react';
import {ActivityIndicator, Dimensions, Text, View} from 'react-native';
import firestore from '@react-native-firebase/firestore';
import Icon from 'react-native-vector-icons/MaterialCommunityIcons';
import FolloweringScreens from './FolloweringScreens';
import {TouchableOpacity} from 'react-native-gesture-handler';

const {width, height} = Dimensions.get('screen');

function Following({urlname, navigation}) {
  const [followingData, setfollowingData] = useState([]);

  // Follower counts, displayname, image
  const fetchData = () => {
    const dataRef = firestore().collection('usernames');

    dataRef
      .doc(urlname)
      .collection('Following')
      .onSnapshot((snapshot) => {
        snapshot.forEach((doc) => {
          dataRef.doc(doc.id.toLowerCase()).onSnapshot((followerDoc) => {
            const data = followerDoc.data();
            setfollowingData((prev) => [
              ...prev,
              {
                profileName: doc.id,
                displayName: data.userName,
                followerCount:
                  data.followers !== undefined ? data.followers : 0,
                followingCount:
                  data.following !== undefined ? data.following : 0,
                image: data.imageUrl ? data.imageUrl : null,
              },
            ]);
          });
        });
      });
  };

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

  return (
    <>
      <View
        style={{
          left: width * 0.04,
          top: 50,
          flexDirection: 'row',
          alignItems: 'center',
          width: '80%',
          height: '4%',
          marginBottom: 5,
        }}>
        {/* {console.log('followin', followingData)} *