React Native：如果我滚动到屏幕顶部，GiftedChat 只会更新聊天消息？答案

【问题标题】：React Native: GiftedChat only updating chat message if I scroll to top of screen?React Native：如果我滚动到屏幕顶部，GiftedChat 只会更新聊天消息？
【发布时间】：2020-06-15 00:06:11
【问题描述】：

我正在将 Gifted Chat 用于使用 React Native 的聊天应用程序。当我发送文本消息或图像时，代码会执行，但新消息不会出现在屏幕上，除非我滚动到聊天屏幕的顶部。如果我滚动到底部，不，如果我只滚动到一半，仍然不。只有当我滚动到屏幕顶部时它才会更新。任何人都明白为什么会发生这种情况？这是我的代码。

import React, { useState } from 'react';
import { Image, StyleSheet, Text, View, Button, FlatList, TouchableOpacity, Alert } from 'react-native';

import { GiftedChat } from 'react-native-gifted-chat';


const Conversation = (props) => {

  const chatId = props.chatId || "12345";
  const userId = props.userId || "6789";
  const [messages, setMessages] = useState([
    {
      _id: 1,
      text: 'My message',
      createdAt: new Date(Date.UTC(2016, 5, 11, 17, 20, 0)),
      user: {
        _id: userId,
        name: 'Jane',
        avatar: 'https://randomuser.me/api/portraits/women/79.jpg',
      }
    },
    {
      _id: 3,
      text: 'My next message',
      createdAt: new Date(Date.UTC(2016, 5, 11, 17, 21, 0)),
      user: {
        _id: 4,
        name: 'Gerry',
        avatar: 'https://randomuser.me/api/portraits/women/4.jpg',
      },
      image: 'https://media1.giphy.com/media/3oEjHI8WJv4x6UPDB6/100w.gif',
    }
  ]);
  const d = Date.now();

  const onSend = (msg) => {
    console.log("msg : ", msg);
    const message = {
      _id: msg[0]._id,
      text: msg[0].text,
      createdAt: new Date(),
      user: {
        _id: userId,
        avatar: "https://randomuser.me/api/portraits/women/79.jpg",
        name: "Jane"
      }
    }
    const arr = messages;
    arr.unshift(message);
    setMessages(arr);
  }

  return (
    <GiftedChat
      messages={messages}
      onSend={newMessage => onSend(newMessage)}
      user={{
        _id: userId,
        name: "Jane",
        avatar: "https://randomuser.me/api/portraits/women/79.jpg"
      }}
    />
  )
}

export default Conversation;

【问题讨论】：

标签： react-native react-native-gifted-chat

【解决方案1】：

想通了。 GiftedChat 要求您使用它自己的方法之一，称为append。

const onSend = (msg) => {
  console.log("msg : ", msg);

  // first, make sure message is an object within an array
  const message = [{
    _id: msg[0]._id,
    text: msg[0].text,
    createdAt: new Date(),
    user: {
      _id: userId,
      avatar: "https://randomuser.me/api/portraits/women/79.jpg",
      name: "Jane"
    }
  }]

  // then, use the GiftedChat method .append to add it to state
  setMessages(previousArr => GiftedChat.append(previousArr, message));
}

【讨论】：