admin管理员组文章数量:1327064
I am developing a chat, as can be seen from the image.
When the chat opens, the chat scrolls down to show the latest messages.
What I would like to do, that when user scrolls up and gets to the last message (i.e. the oldest one in the chat), the oldMessage function is called which makes an http call passing the current page to try to retrieve the previous messages to the last displayed at the top.
I don't know if I've made myself clear.
Can you give me a hand?
Link: codesandbox
import React, { useState, useRef, useEffect } from "react";
import { makeStyles } from "@material-ui/core/styles";
import {
Card,
Typography,
Icon,
useTheme,
TextField,
IconButton,
Avatar,
Paper
} from "@material-ui/core";
import Moment from "react-moment";
import clsx from "clsx";
import moment from "moment/moment";
const message = [
{
id: 1,
createdAt: "",
message: "Hi, James!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 2,
createdAt: "",
message: "Hi, Vesper!",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
},
{
id: 3,
createdAt: "",
message: "Quickly e to the meeting room 1B, we have a big server issue",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 4,
createdAt: "",
message: "I’m having breakfast right now, can’t you wait for 10 minutes?",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
},
{
id: 5,
createdAt: "",
message: "I’m having breakfast right now, can’t you wait for 10 minutes?",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
},
{
id: 6,
createdAt: "",
message: "We are losing money! Quick!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 7,
createdAt: "",
message:
"It’s not my money, you know. I will eat my breakfast and then I will e to the meeting room.",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
},
{
id: 8,
createdAt: "",
message: "You are the worst!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 9,
createdAt: "",
message: "We are losing money! Quick!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 10,
createdAt: "",
message: "You are the worst!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 11,
createdAt: "",
message: "We are losing money! Quick!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 12,
createdAt: "",
message:
"It’s not my money, you know. I will eat my breakfast and then I will e to the meeting room.",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
}
];
const useStyles = makeStyles((theme) => ({
root: {
"& > *": {
margin: theme.spacing(1)
}
},
messageRow: {
position: "relative",
display: "flex",
flexDirection: "column",
alignItems: "flex-start",
justifyContent: "flex-end",
padding: "0 16px 4px 16px",
flex: "0 0 auto",
"&.contact": {
"& $bubble": {
backgroundColor: theme.palette.background.paper,
color: theme.palette.getContrastText(theme.palette.background.paper),
borderTopLeftRadius: 5,
borderBottomLeftRadius: 5,
borderTopRightRadius: 20,
borderBottomRightRadius: 20,
marginLeft: 28,
"& $time": {
marginLeft: 12
}
},
"&.first-of-group": {
"& $bubble": {
borderTopLeftRadius: 20
}
},
"&.last-of-group": {
"& $bubble": {
borderBottomLeftRadius: 20
}
}
},
"&.me": {
paddingLeft: 40,
"& $avatar": {
order: 2,
margin: "0 0 0 16px"
},
"& $bubble": {
marginLeft: "auto",
backgroundColor: theme.palette.primary.main,
color: theme.palette.primary.contrastText,
borderTopLeftRadius: 20,
borderBottomLeftRadius: 20,
borderTopRightRadius: 5,
borderBottomRightRadius: 5,
"& $time": {
justifyContent: "flex-end",
right: 0,
marginRight: 12
}
},
"&.first-of-group": {
"& $bubble": {
borderTopRightRadius: 20
}
},
"&.last-of-group": {
"& $bubble": {
borderBottomRightRadius: 20
}
}
},
"&.contact + .me, &.me + .contact": {
paddingTop: 20,
marginTop: 20
},
"&.first-of-group": {
"& $bubble": {
borderTopLeftRadius: 20,
paddingTop: 13
}
},
"&.last-of-group": {
"& $bubble": {
borderBottomLeftRadius: 20,
paddingBottom: 13,
"& $time": {
display: "flex"
}
}
}
},
avatar: {
position: "absolute",
left: 0,
margin: 0
},
bubble: {
position: "relative",
display: "flex",
alignItems: "center",
justifyContent: "center",
padding: 12,
maxWidth: "100%",
boxShadow: theme.shadows[1]
},
message: {
whiteSpace: "pre-wrap",
lineHeight: 1.2
},
time: {
position: "absolute",
display: "none",
width: "100%",
fontSize: 11,
marginTop: 8,
top: "100%",
left: 0,
whiteSpace: "nowrap"
},
bottom: {
// background: theme.palette.background.default,
// borderTop: '1px solid rgba(0, 0, 0, 0.13)'
},
inputWrapper: {
borderRadius: 24
}
}));
export default function App() {
const classes = useStyles();
const [state, setState] = useState({
userMyInfo: {
id: 1,
name: "James",
surname: "Bond"
},
chat: message,
msgState: "",
pag: 0
});
const { userMyInfo, chat, msgState } = state;
const sendMessage = () => {};
const oldMessage = () => {
//http request
fetch("")
.then((response) => response.json())
.then((message) => {
setState(...(prev) => ({ ...prev, chat: [...message, ...prev.chat] }));
})
.catch((error) => {
console.error(error);
});
};
const messagesEndRef = useRef(null);
const scrollToBottom = () => {
messagesEndRef.current.scrollIntoView({ behavior: "smooth" });
};
useEffect(scrollToBottom, []);
const shouldShowContactAvatar = (item, i) => {
return (
(chat[i + 1] && chat[i].senderId._id !== chat[i + 1].senderId._id) ||
!chat[i + 1]
);
};
const isFirstMessageOfGroup = (item, i) => {
return (
i === 0 || (chat[i - 1] && chat[i - 1].senderId._id !== item.senderId._id)
);
};
const isLastMessageOfGroup = (item, i) => {
return (
i === chat.length - 1 ||
(chat[i + 1] && chat[i + 1].senderId._id !== item.senderId._id)
);
};
return (
<Paper
elevation={3}
className={clsx(classes.root, "flex flex-col relative pb-64")}
>
<Card elevation={1} className="flex flex-col h-512 rounded-8">
<div
className="flex flex-shrink-0 items-center justify-between px-24 h-64"
style={{
background: "#607d8b"
//color: theme.palette.getContrastText('#607d8b')
}}
>
<Typography className="text-center text-16 font-400">Chat</Typography>
</div>
<div style={{ flex: 1, overflowY: "auto" }}>
{state.chat.length === 0 ? (
<div style={{ textAlign: "center" }}>
Al momento non ci sono messaggi
</div>
) : (
state.chat.map((item, key) => (
<div
key={key}
className={clsx(
classes.messageRow,
{ me: item.senderId._id === userMyInfo.id },
{ contact: item.senderId._id !== userMyInfo.id },
{ "first-of-group": isFirstMessageOfGroup(item, key) },
{ "last-of-group": isLastMessageOfGroup(item, key) }
)}
>
{item.senderId._id !== userMyInfo.id &&
shouldShowContactAvatar(item, key) && (
<Avatar className={classes.avatar}>
{item.senderId.name[0]} {item.senderId.surname[0]}
</Avatar>
)}
<div className={classes.bubble}>
<div className={classes.message}>{item.message}</div>
<Typography className={classes.time} color="textSecondary">
{moment(item.time).format("MMMM Do YYYY, h:mm:ss a")}
</Typography>
</div>
</div>
))
)}
<div ref={messagesEndRef} />
</div>
<div style={{ padding: 5, display: "flex", flexDirection: "row" }}>
<TextField
required
id="outlined-required"
label="Message"
//inputRef={textInput}
placeholder="Message"
//onChange={handleChange}
variant="outlined"
fullWidth
/>
<IconButton onClick={() => sendMessage()} disabled={msgState === ""}>
<Icon>send</Icon>
</IconButton>
</div>
</Card>
</Paper>
);
}
I am developing a chat, as can be seen from the image.
When the chat opens, the chat scrolls down to show the latest messages.
What I would like to do, that when user scrolls up and gets to the last message (i.e. the oldest one in the chat), the oldMessage function is called which makes an http call passing the current page to try to retrieve the previous messages to the last displayed at the top.
I don't know if I've made myself clear.
Can you give me a hand?
Link: codesandbox
import React, { useState, useRef, useEffect } from "react";
import { makeStyles } from "@material-ui/core/styles";
import {
Card,
Typography,
Icon,
useTheme,
TextField,
IconButton,
Avatar,
Paper
} from "@material-ui/core";
import Moment from "react-moment";
import clsx from "clsx";
import moment from "moment/moment";
const message = [
{
id: 1,
createdAt: "",
message: "Hi, James!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 2,
createdAt: "",
message: "Hi, Vesper!",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
},
{
id: 3,
createdAt: "",
message: "Quickly e to the meeting room 1B, we have a big server issue",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 4,
createdAt: "",
message: "I’m having breakfast right now, can’t you wait for 10 minutes?",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
},
{
id: 5,
createdAt: "",
message: "I’m having breakfast right now, can’t you wait for 10 minutes?",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
},
{
id: 6,
createdAt: "",
message: "We are losing money! Quick!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 7,
createdAt: "",
message:
"It’s not my money, you know. I will eat my breakfast and then I will e to the meeting room.",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
},
{
id: 8,
createdAt: "",
message: "You are the worst!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 9,
createdAt: "",
message: "We are losing money! Quick!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 10,
createdAt: "",
message: "You are the worst!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 11,
createdAt: "",
message: "We are losing money! Quick!",
senderId: {
_id: 2,
name: "Vesper",
surname: "Lynd"
}
},
{
id: 12,
createdAt: "",
message:
"It’s not my money, you know. I will eat my breakfast and then I will e to the meeting room.",
senderId: {
_id: 1,
name: "James",
surname: "Bond"
}
}
];
const useStyles = makeStyles((theme) => ({
root: {
"& > *": {
margin: theme.spacing(1)
}
},
messageRow: {
position: "relative",
display: "flex",
flexDirection: "column",
alignItems: "flex-start",
justifyContent: "flex-end",
padding: "0 16px 4px 16px",
flex: "0 0 auto",
"&.contact": {
"& $bubble": {
backgroundColor: theme.palette.background.paper,
color: theme.palette.getContrastText(theme.palette.background.paper),
borderTopLeftRadius: 5,
borderBottomLeftRadius: 5,
borderTopRightRadius: 20,
borderBottomRightRadius: 20,
marginLeft: 28,
"& $time": {
marginLeft: 12
}
},
"&.first-of-group": {
"& $bubble": {
borderTopLeftRadius: 20
}
},
"&.last-of-group": {
"& $bubble": {
borderBottomLeftRadius: 20
}
}
},
"&.me": {
paddingLeft: 40,
"& $avatar": {
order: 2,
margin: "0 0 0 16px"
},
"& $bubble": {
marginLeft: "auto",
backgroundColor: theme.palette.primary.main,
color: theme.palette.primary.contrastText,
borderTopLeftRadius: 20,
borderBottomLeftRadius: 20,
borderTopRightRadius: 5,
borderBottomRightRadius: 5,
"& $time": {
justifyContent: "flex-end",
right: 0,
marginRight: 12
}
},
"&.first-of-group": {
"& $bubble": {
borderTopRightRadius: 20
}
},
"&.last-of-group": {
"& $bubble": {
borderBottomRightRadius: 20
}
}
},
"&.contact + .me, &.me + .contact": {
paddingTop: 20,
marginTop: 20
},
"&.first-of-group": {
"& $bubble": {
borderTopLeftRadius: 20,
paddingTop: 13
}
},
"&.last-of-group": {
"& $bubble": {
borderBottomLeftRadius: 20,
paddingBottom: 13,
"& $time": {
display: "flex"
}
}
}
},
avatar: {
position: "absolute",
left: 0,
margin: 0
},
bubble: {
position: "relative",
display: "flex",
alignItems: "center",
justifyContent: "center",
padding: 12,
maxWidth: "100%",
boxShadow: theme.shadows[1]
},
message: {
whiteSpace: "pre-wrap",
lineHeight: 1.2
},
time: {
position: "absolute",
display: "none",
width: "100%",
fontSize: 11,
marginTop: 8,
top: "100%",
left: 0,
whiteSpace: "nowrap"
},
bottom: {
// background: theme.palette.background.default,
// borderTop: '1px solid rgba(0, 0, 0, 0.13)'
},
inputWrapper: {
borderRadius: 24
}
}));
export default function App() {
const classes = useStyles();
const [state, setState] = useState({
userMyInfo: {
id: 1,
name: "James",
surname: "Bond"
},
chat: message,
msgState: "",
pag: 0
});
const { userMyInfo, chat, msgState } = state;
const sendMessage = () => {};
const oldMessage = () => {
//http request
fetch("")
.then((response) => response.json())
.then((message) => {
setState(...(prev) => ({ ...prev, chat: [...message, ...prev.chat] }));
})
.catch((error) => {
console.error(error);
});
};
const messagesEndRef = useRef(null);
const scrollToBottom = () => {
messagesEndRef.current.scrollIntoView({ behavior: "smooth" });
};
useEffect(scrollToBottom, []);
const shouldShowContactAvatar = (item, i) => {
return (
(chat[i + 1] && chat[i].senderId._id !== chat[i + 1].senderId._id) ||
!chat[i + 1]
);
};
const isFirstMessageOfGroup = (item, i) => {
return (
i === 0 || (chat[i - 1] && chat[i - 1].senderId._id !== item.senderId._id)
);
};
const isLastMessageOfGroup = (item, i) => {
return (
i === chat.length - 1 ||
(chat[i + 1] && chat[i + 1].senderId._id !== item.senderId._id)
);
};
return (
<Paper
elevation={3}
className={clsx(classes.root, "flex flex-col relative pb-64")}
>
<Card elevation={1} className="flex flex-col h-512 rounded-8">
<div
className="flex flex-shrink-0 items-center justify-between px-24 h-64"
style={{
background: "#607d8b"
//color: theme.palette.getContrastText('#607d8b')
}}
>
<Typography className="text-center text-16 font-400">Chat</Typography>
</div>
<div style={{ flex: 1, overflowY: "auto" }}>
{state.chat.length === 0 ? (
<div style={{ textAlign: "center" }}>
Al momento non ci sono messaggi
</div>
) : (
state.chat.map((item, key) => (
<div
key={key}
className={clsx(
classes.messageRow,
{ me: item.senderId._id === userMyInfo.id },
{ contact: item.senderId._id !== userMyInfo.id },
{ "first-of-group": isFirstMessageOfGroup(item, key) },
{ "last-of-group": isLastMessageOfGroup(item, key) }
)}
>
{item.senderId._id !== userMyInfo.id &&
shouldShowContactAvatar(item, key) && (
<Avatar className={classes.avatar}>
{item.senderId.name[0]} {item.senderId.surname[0]}
</Avatar>
)}
<div className={classes.bubble}>
<div className={classes.message}>{item.message}</div>
<Typography className={classes.time} color="textSecondary">
{moment(item.time).format("MMMM Do YYYY, h:mm:ss a")}
</Typography>
</div>
</div>
))
)}
<div ref={messagesEndRef} />
</div>
<div style={{ padding: 5, display: "flex", flexDirection: "row" }}>
<TextField
required
id="outlined-required"
label="Message"
//inputRef={textInput}
placeholder="Message"
//onChange={handleChange}
variant="outlined"
fullWidth
/>
<IconButton onClick={() => sendMessage()} disabled={msgState === ""}>
<Icon>send</Icon>
</IconButton>
</div>
</Card>
</Paper>
);
}
- So, you want to call a method when your container is scrolled to top? – Nadia Chibrikova Commented Dec 13, 2020 at 18:00
- @nadia: Yes, just like you do in chats, when you go up to the last message the oldest received should take the messages that proceeded calling a function. Except it's not the whole page I'm interested in, but one div in particular. – Paul Commented Dec 14, 2020 at 10:03
2 Answers
Reset to default 6You need to add an event handler for scrolling and check you are at the top of the container
const handleScroll = e => {
let element = e.target;
if (element.scrollTop===0) {
//fetch messages
}
}
<div style={{ flex: 1, overflowY: "auto"}} onScroll={ handleScroll}>
Two things you can do is
Monitor for scroll event on an element using onScroll from react
<ScrollableComponent onScroll={this.handleScroll} />use the windows scroll event handler and detect when user is at top of page
useEffect(() => { window.addEventListener('scroll', this.handleScroll); return () => window.removeEventListener('scroll', this.handleScroll); }const handleScroll = (event) => { // code here }
本文标签： javascriptReact js chat when scrolling up load old messagesStack Overflow
版权声明：本文标题：javascript - React js chat when scrolling up load old messages - Stack Overflow 内容由网友自发贡献，该文观点仅代表作者本人， 转载请联系作者并注明出处：http://www.betaflare.com/web/1742212519a2433975.html， 本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌抄袭侵权/违法违规的内容，一经查实，本站将立刻删除。
发表评论