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How to push data in the setState of array-type state?

I am having a state data. I wanted to push a new entry of the form
{ task:'ANy task',key:Math.random().toString() }
in the data array while using setData.
I had tried many ways mentioned here, but don't klnow why its not working.
Here's my code.
import React, { useState } from "react";
import { StyleSheet, Text, View, TextInput, Button } from "react-native";
import { StatusBar } from "expo-status-bar";
const Addtask = ({navigation}) => {
const [data,setData] = useState([]);
console.log("from add = ",data)
const [task, setTask] = useState("");
const handleSubmit = () => {
console.log("submit pressed for task = ", task)
const updatedData = [...data,{
task:task,
key: Math.random().toString(),
}]
//here i am setting the data
setData(prevState => [...prevState,updatedData]);
console.log("data after adding task",data)
navigation.navigate("Tasklist",{data:data})
}
return (
<View style={styles.container}>
<StatusBar style="light" backgroundColor="midnightblue" />
<View>
<Text style={styles.text}>Add Task Here</Text>
</View>
<View>
<TextInput
style={styles.input}
onChangeText={setTask}
value={task}
onChange={setTask}
placeholder="Type your task"
keyboardType="ascii-capable"
/>
</View>
<View style={styles.buttoms}>
<View style={{margin:4}}>
<Button color={'red'} onPress={()=>{navigation.goBack()}} title="Cancel"></Button>
</View>
<View style={{margin:4}}>
<Button color={'lightblue'} onPress={()=>setTask('')} title="Clear"></Button>
</View>
<View style={{margin:4}}>
<Button color={'green'} onPress={handleSubmit} title="Save"></Button>
</View>
</View>
</View>
);
};
const styles = StyleSheet.create({
.
.
.
});
export default Addtask;
To debug, I had used console stmts which reveals that the task value is coming in the handleSubmit() correctly but it is not getting pushed.
Log
submit pressed for task = Morning bike ride.
data after adding task Array []

Because You are already have
const updatedData = [...data,{
task:task,
key: Math.random().toString(),
}]
You don't need setData(prevState => [...prevState,updatedData]) you can just assign the updatedData to setData like setData(updatedData)
You can use
setData(current => [...current, {
task:task,
key: Math.random().toString(),
}])
Then you don't need updatedData

Share QR React Native

I'm new in react/react native. I'm trying to share a QR Code as image.
Generate QR works, but I want to share it as an image (whatsapp, bluetooth, etc).
import QRCode from 'react-native-qrcode-svg';
let svg = useRef();
//let svg = '';
<QRCode
size={300}
value={`${name}`}
getRef={(c) => (svg = c)}
/>
I tried "get base64 string encode of the qrcode" from official documentation, but I just don't get it
//From Off Doc
getDataURL() {
this.svg.toDataURL(this.callback);
}
callback(dataURL) {
console.log(dataURL);
}
What I tried to do (all my code):
import React, { useRef } from 'react';
import QRCode from 'react-native-qrcode-svg';
const QR = ({ name }: any) => {
let svg = useRef();
const getDataURL = () => {
svg.toDataURL(callback(dataURL));
//console.log(svg);
}
callback(dataURL) {
console.log(dataURL);
}
return (
<>
<QRCode
size={300}
value={`${name}`}
getRef={(c) => (svg = c)}
/>
<Button onPress={getDataURL}
title="Call Funct"
color="#1FAAE2" />
</>
);
get error svg.toDataURL is not a function.
I have been in this for days, I also read another stackover queries with the same problem but solutions in those questions didn't work for me. Thank you in advance guys
Error toDataURL
console.log(svg)

I have changed a couple of things in your code and used it on a expo app where I installed react-native-qrcode-svg and react-native-svg
import { StatusBar } from "expo-status-bar";
import { StyleSheet, Text, View, TextInput, Button } from "react-native";
import { useRef } from "react";
import QRCode from "react-native-qrcode-svg";
const QR = ({ name }: any) => {
let svg = useRef<SVG>(null);
const getDataURL = () => {
svg?.toDataURL(callback);
//console.log(svg);
};
function callback(dataURL: string) {
console.log(dataURL);
}
return (
<>
<QRCode size={300} value={`${name}`} getRef={(c) => (svg = c)} />
<Button onPress={getDataURL} title="Call Funct" color="#1FAAE2" />
</>
);
};
export default function App() {
const input = useRef<TextInput>(null);
return (
<View style={styles.container}>
<Text>Open up App.tsx to start working on your app!</Text>
<StatusBar style="auto" />
<QR />
</View>
);
}
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: "#fff",
alignItems: "center",
justifyContent: "center",
},
});
Main changes from your code is defining the callback as a function
// you had
callback(dataURL) {
console.log(dataURL);
}
// but it should be
function callback(dataURL) {
console.log(dataURL);
}
// or
const callback = (dataURL) => {
console.log(dataURL)
}
and doing the call properly on getDataURL
// you had
svg.toDataURL(callback(dataURL));
// but it should be
svg.toDataURL(callback);
After those changes clicking in the button returns the dataURL in the console as expected.
Old answer before question edit:
Your issue seems to be that svg is not defined when you call svg.toDataURL how are you calling the function? If you are doing that on the first render it is possible that the ref is not ready yet.
If you are doing that using a callback in a button in the screen then the issue should be around the code setting the ref.
Can you post your whole component?

My solution with typescript: I needed to add
'// #ts-ignore' because I used Typescript
import React, { useRef } from 'react';
import QRCode from 'react-native-qrcode-svg';
import { TouchableOpacity, Text } from 'react-native';
export const Screen1 = ( ) => {
const svg = useRef();
const getDataURL = () => {
// #ts-ignore
svg.current?.toDataURL(callback);
};
const callback = (dataURL: string) => {
console.log( dataURL );
}
return (
<>
<QRCode
value={ "Some String" }
size={ 250 }
color="black"
backgroundColor="white"
getRef={(c: any) => ( svg.current = c )}
/>
<TouchableOpacity
activeOpacity={ 0.8 }
style={ styles.Button }
onPress={() => getDataURL() }
>
<Text style={ styles.Text }> Press </Text>
</TouchableOpacity>
</>
)

You get the function not found error when you testing it with web, test it with iOS simulator then it will work.

firebase realtime database is not getting fetched with onPress in react native, have to refresh the ref().on function everytime

I have a realtime database with main node 'user' and then inside it i have 3 child nodes and those 3 child nodes have 4 more child nodes, each of them. One of the 4 nodes is a recording, one is image and 2 of them are strings. I am trying to fetch them dynamically with Next and Back button where on pressing next, next node's data is displayed on screen.
I am using a useState for dynamically changing the path of database (ref), but on pressing the next/back button, my data on screen does not get updated. Also later I found out that after pressing next/back button when I refresh/rewrite the ref().on function, my data gets updated, but I have to do this for every press.
Here's my App.js code:
import Sound from 'react-native-sound';
import database from '#react-native-firebase/database';
import storage from '#react-native-firebase/storage';
import React , {useEffect, useState} from 'react';
import {
ScrollView,
StyleSheet,
Alert,
Text,
View,
Image,
Button
} from 'react-native';
const App = () => {
const [myData,setData] = useState({
letter:'',
pronun:'',
word:'',
image:''
});
const [img,setimg] = useState(null);
const [pronunn,setpronun] = useState(null);
const [hey,sethey] = useState(1);
useEffect(() => {
getDatabase();
}, []);
function getDatabase() {
database().ref('users/'+hey+'/').on('value' , (snapshot) => {
Sound.setCategory('Playback', true);
var poo=new Sound(snapshot.val().pronun);
setData({
letter: snapshot.val().letter,
word: snapshot.val().word,
image: setimg(snapshot.val().image),
pronun: setpronun(poo)
});
console.log(snapshot.val());
});
}
return (
<View style={{flex:1, backgroundColor:'#000000', alignContent:'center', alignItems:'center', justifyContent:'center'}}>
<ScrollView>
<Text style={{color:'#ffff'}}>
Letter: {myData ? myData.letter : 'loading...' }
</Text>
<Text style={{color:'#ffff'}}>
Word: {myData ? myData.word : 'loading...' }
</Text>
<Image style={{width:200, height:200}}
source={{uri: img}}
/>
<View>
<Button
title='Pronunciation'
onPress={() => {
return pronunn.play();
}}
>
</Button>
<Button title='Next' onPress={
() => {
if (hey>2) {
Alert.alert('no more records');
}
else {
return sethey(hey+1);
}
}
}
>
</Button>
<Button title='back' onPress={
() => {
if (hey<2) {
Alert.alert('no more records to go back');
}
else {
return sethey(hey-1);
}
}
}
>
</Button>
</View>
</ScrollView>
</View>
);
};
export default App;

Since your setData hook/effect depends on the hey state, you need to specify the latter as a dependency in useEffect for the data loading.
useEffect(() => {
getDatabase();
}, [hey]);
Also see:
The documentation on useEffect, specifically the section on dependencies.
setState in React's useEffect dependency array

why my react native component keep refreshing?

hi i am trying to build react native app i am using expo
i build a screen to show data and calculate a number using hooks
but i face that my component keep rendering so i cant press in the buttons easily , which lead me to can't calculate the number ,
this is my code how i can stop this continuous refreshing
if i but console statements inside the component it keep printing in console and not stop
import React, { useState, useEffect } from "react";
import { AsyncStorage } from "react-native";
import { Button } from "react-native-paper";
import axios from "axios";
import { View, Text, TextInput, StyleSheet } from "react-native";
export default function Confirm() {
const [info, setInfo] = useState([]);
const [value, onChangeText] = React.useState("0");
const [total, setTotal] = useState("0");
const [selectedLocation, setSelectedLocation] = useState({});
try {
//Retrieving user token, reserved nanny information and user location value from AsyncStorage
AsyncStorage.multiGet(["token", "nany", "location"]).then((res) => {
var nany = JSON.parse(res[1][1]);
var location = JSON.parse(res[2][1]);
setInfo(nany);
console.log("hi3");
setSelectedLocation(location);
});
} catch (error) {
throw error;
}
const onSubmit = () => {
axios
.post("http://192.168.127.43:5000/send2", [selectedLocation, total, info])
.then(function (response) {
console.log(response);
})
.catch(function (error) {
console.log(error);
});
};
function calculateTotal() {
console.log(info.cost * value);
var totalCost = info.cost * value;
setTotal(totalCost);
alert("Your reservation done \n Your service costs: " + total);
}
return (
<View>
<>
<View>
<Card
title={info.name}
caption={info.cost + " JD /H"}
>
<View
>
<Text>{info.place}</Text>
</View>
</Card>
<View>
<View>
<Text style={styles.text}>
Enter how many hours you need our service
</Text>
<TextInput
style={styles.input}
onChangeText={(text) => onChangeText(text)}
value={value}
></TextInput>
</View>
<View>
<Button
mode="contained"
onPress={calculateTotal}
>
<Text>Calculate total</Text>
</Button>
</View>
</View>
<View>
<View>
<Button
mode="contained"
onPress={onSubmit}
>
<Text>Done</Text>
</Button>
</View>
<View>
<Button
title="Submit"
mode="contained"
>
<Text>Cancel</Text>
</Button>
</View>
</View>
</View>
</>
</View>
);
}
// export default Confirm;

Nothing looks wrong in your code but for safer side wrap try and catch inside useEffect.
useEffect(()=>{
try {
//Retrieving user token, reserved nanny information and user location value from AsyncStorage
AsyncStorage.multiGet(["token", "nany", "location"]).then((res) => {
var nany = JSON.parse(res[1][1]);
var location = JSON.parse(res[2][1]);
setInfo(nany);
console.log("hi3");
setSelectedLocation(location);
});
} catch (error) {
throw error;
}
,[]);

Conditional rendering with React Hooks : loading

I am learning how to use React Hooks and have been stuck for many hours on something that's supposed to be very simple.
I am trying to display a a text if the state variable "loading" is true. If it's false, I want to display something else.
No matter what I try, "loading" is always false or at least, the UI does not appear to reflect its value.
here is the code:
import React, {useState, useEffect} from 'react';
import {View, SafeAreaView, Text} from 'react-native';
const testScreen= (props) => {
const [loading, setLoading ] = useState(true);
useEffect(() => {
setLoading(false);
}, []);
if(loading)
{
return <Text>Hi</Text>;
}
else
{
return<Text.Hey</Text>
}
}
export default testScreen;
Any help will be more than welcome and I am sorry if this is very basic.
UPDATE: Here is the actual code I am working with. SetLoading is supposed to update the state variable to false but never does or at least, the UI des not render.
import React, {useState, useEffect} from 'react';
import {View, SafeAreaView, Text, ActivityIndicator} from 'react-native';
import CategoryTag from '../Components/CategoryTag';
import firestore from '#react-native-firebase/firestore';
const CategoryScreen = (props) => {
const topicCollection = firestore().collection('Topics')
.where("active","==",true);
//hooks for topics
const [topics,setTopics] = useState([]);
const [loading, setLoading ] = useState(true);
//get all active topics
useEffect(() => {
return topicCollection.onSnapshot(querySnapshot => {
const list = [];
querySnapshot.forEach(doc => {
const { active, name } = doc.data();
list.push({
id: doc.id,
active,
name,
});
});
setTopics(list);
setLoading(false);
});
}, []);
const renderTopics = () =>{
return(
topics.map((item) =>{
return(
<CategoryTag key = {item.id}
color={userTopics.includes(item.name) ?"#51c0cc":"#303239"}
name = {item.name}
isSelected = {userTopics.includes(item.name)}
handleClick = {addTopicToUserTopicCollection}
/>
)
})
)
}
if(loading)
{
return (
<SafeAreaView style={{flex:1, backgroundColor:"#455a65"}}>
<View style={{width:200, padding:20, paddingTop:60}}>
<Text style ={{fontSize:25, fontWeight:"bold",
color:"#fff"}}>What are you</Text>
<Text style ={{fontSize:22, color:"#fff"}}>interested in?
</Text>
</View>
<View style={{flex:1, alignItems:"center",
justifyContent:"center", alignSelf:"center"}}>
<ActivityIndicator />
</View>
</SafeAreaView>
)
}
else // this never runs
{
return (
<SafeAreaView style={{flex:1, backgroundColor:"#455a65"}}>
<View>
<View style={{width:200, padding:20, paddingTop:60}}>
<Text style ={{fontSize:25, fontWeight:"bold",
color:"#fff"}}>What are you</Text>
<Text style ={{fontSize:22, color:"#fff"}}>interested in?
</Text>
</View>
<View style ={{flexDirection:"column", paddingTop:20}}>
<View style ={{padding:15, paddingTop:15,
marginBottom:15,
flexWrap:"wrap", flexDirection:"row"}}>
{renderTopics(topics)}
</View>
</View>
</View>
</SafeAreaView>
);
}
}
export default CategoryScreen;

You are immediately setting your setLoading state to false and therefore loading text might be rendering for fraction of second, or not at all, like a glitch. Try setting setLoading with a timeout and then you will see the intended behaviour.
const TestScreen= (props) => {
const [loading, setLoading ] = useState(true);
useEffect(() => {
setTimeout(()=>setLoading(false), 3000);
}, []);
if(loading)
{
return <Text>Hi</Text>;
}
else
{
return<Text>hey</Text>
}
}