Develop Reference

How to save route.params with asyncstorage?

Srry if the title makes no sense. Don't know a better title.
How can I save route.params items that I pass to my second screen using AsyncStorage?
In my first screen i have a bunch of data in a FlatList that can be opened with a Modal. Inside that Modal I have a TouchableOpacity that can send the data thats inside the Modal to my second screen. The data that has been passed to the second screen is passed to a FlatList. The data in the FlatList should be saved to AsyncStorage. Tried alot of things getting this to work, but only getting warning message
undefined. Code below is the most recent progress.
Using React Navigation V5.
FIRST SCREEN
const [masterDataSource, setMasterDataSource] = useState(DataBase);
const [details, setDetails] = useState('');
<TouchableOpacity
onPress={() => {
const updated = [...masterDataSource];
updated.find(
(item) => item.id === details.id,
).selected = true;
setMasterDataSource(updated);
navigation.navigate('cart', {
screen: 'cart',
params: {
items: updated.filter((item) => item.selected),
},
});
setModalVisible(false);
}}>
<Text>Add to cart</Text>
</TouchableOpacity>
SECOND SCREEN
import React, { useEffect, useState } from 'react';
import { View, Text, FlatList, TouchableOpacity } from 'react-native';
import { useTheme } from '../Data/ThemeContext';
import AsyncStorage from '#react-native-async-storage/async-storage';
import Ionicons from 'react-native-vector-icons/Ionicons';
export default function ShoppingList({ route, navigation }) {
const [shoppingList, setShoppingList] = useState([]);
const { colors } = useTheme();
const todo = () => {
alert('Todo');
};
useEffect(() => {
restoreShoppingListAsync();
}, []);
const shoppingListAsync = () => {
const shoppingList = route.params && route.params.items;
setShoppingList(list);
storeShoppingList(list);
};
const asyncStorageKey = '#ShoppingList';
const storeShoppingListAsync = (list) => {
const stringifiedList = JSON.stringify(list);
AsyncStorage.setItem(asyncStorageKey, stringifiedList).catch((err) => {
console.warn(err);
});
};
const restoreShoppingListAsync = () => {
AsyncStorage.getItem(asyncStorageKey)
.then((stringifiedList) => {
console.log(stringifiedList);
const parsedShoppingList = JSON.parse(stringifiedList);
if (!parsedShoppingList || typeof parsedShoppingList !== 'object')
return;
setShoppingList(parsedShoppingList);
})
.then((err) => {
console.warn(err);
});
};
const RenderItem = ({ item }) => {
return (
<View>
<TouchableOpacity
style={{
marginLeft: 20,
marginRight: 20,
elevation: 3,
backgroundColor: colors.card,
borderRadius: 10,
}}>
<View style={{ margin: 10 }}>
<Text style={{ color: colors.text, fontWeight: '700' }}>
{item.name}
</Text>
<Text style={{ color: colors.text }}>{item.gluten}</Text>
<Text style={{ color: colors.text }}>{item.id}</Text>
</View>
</TouchableOpacity>
</View>
);
};
const emptyComponent = () => {
return (
<View style={{ alignItems: 'center' }}>
<Text style={{ color: colors.text }}>Listan är tom</Text>
</View>
);
};
const itemSeparatorComponent = () => {
return (
<View
style={{
margin: 3,
}}></View>
);
};
return (
<View
style={{
flex: 1,
}}>
<View
style={{
padding: 30,
backgroundColor: colors.Textinput,
elevation: 12,
}}>
<View style={{ flexDirection: 'row', justifyContent: 'space-between' }}>
<TouchableOpacity onPress={() => navigation.goBack()}>
<Ionicons name="arrow-back-outline" size={25} color="#fff" />
</TouchableOpacity>
<Text style={{ color: '#fff', fontSize: 20 }}>Inköpslista</Text>
<TouchableOpacity>
<Ionicons
name="trash-outline"
size={25}
color="#fff"
onPress={() => todo()}
/>
</TouchableOpacity>
</View>
</View>
<View style={{ flex: 1, marginTop: 30 }}>
<FlatList
data={shoppingList}
renderItem={RenderItem}
ListEmptyComponent={emptyComponent}
ItemSeparatorComponent={itemSeparatorComponent}
initialNumToRender={4}
maxToRenderPerBatch={5}
windowSize={10}
removeClippedSubviews={true}
updateCellsBatchingPeriod={100}
showsVerticalScrollIndicator={true}
contentContainerStyle={{ paddingBottom: 20 }}
/>
</View>
</View>
);
}

As you are using async storage to maintain the cart.
I would suggest an approach as below
Update the asyn storage when new items are added to or removed from the cart
Retrieve the items from the cart screen and show the items there
Before you navigate store the items like below
AsyncStorage.setItem(
'Items',
JSON.stringify(updated.filter((item) => item.selected))
).then(() => {
navigation.navigate('Cart', {
items: updated.filter((item) => item.selected),
});
});
The cart screen would be something like below
function Cart({ navigation, route }) {
const [data,setData]=useState([]);
React.useEffect(() => {
async function fetchMyAPI() {
const value = await AsyncStorage.getItem('Items');
setData(JSON.parse(value));
}
fetchMyAPI();
}, []);
return (
<View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
<Button title="Go back" onPress={() => navigation.goBack()} />
<FlatList
data={data}
renderItem={RenderItem}
/>
</View>
);
}
Working Example
https://snack.expo.io/#guruparan/cartexample

Pass JSON data into another screen

1
I am a beginner and still learning to react native.
In my react native App, I have 2 screens. In the first page, I have JSON data ; I want to pass this JSON data to the next page.
I used react-navigation for navigating between pages. I need to passed each parameter for a new book screen for each book.
But I couldn't figure out, how to pass JSON data to next page! In BookScreen.js the function "getParam" is not been seen.
First Screen: ExploreScreen.js
import React, { useState, useEffect } from "react";
import {
View,
Text,
StyleSheet,
FlatList,
Image,
TouchableOpacity,
} from "react-native";
export default function ExploreScreen({ navigation, route }) {
const [data, setData] = useState([]);
useEffect(() => {
loadData();
}, []);
const loadData = async () => {
await fetch(
"http://www.json-generator.com/api/json/get/bTvNJudCPS?indent=2"
)
.then((response) => response.json())
.then((receivedData) => setData(receivedData));
};
return (
<View style={styles.container}>
<FlatList
data={data}
renderItem={({ item }) => (
<TouchableOpacity
style={styles.book}
onPress={() => navigation.navigate("Book", item)}
>
<Image
style={styles.bookImage}
source={{ uri: item.book_image }}
></Image>
<View>
<Text style={styles.bookTitleText}>{item.title}</Text>
<Text style={styles.bookAuthor}>{item.author}</Text>
<Text style={styles.bookGenre}>
<Text styles={styles.gen}>Genul: </Text>
{item.genre_id}
</Text>
</View>
</TouchableOpacity>
)}
></FlatList>
</View>
);
}
const styles = StyleSheet.create({
container: {
flex: 1,
alignItems: "center",
alignSelf: "center",
paddingVertical: "15%",
},
book: {
flex: 1,
flexDirection: "row",
marginBottom: 3,
},
bookImage: {
width: 100,
height: 100,
margin: 5,
},
bookTitleText: {
color: "#8B0000",
fontSize: 15,
fontStyle: "italic",
fontWeight: "bold",
},
bookAuthor: {
color: "#F41313",
},
});
Second Screen: BookScreen.js
import React from "react";
import { View, Text, StyleSheet } from "react-native";
export default function BookScreen({ navigation, route }) {
const { item } = route.params;
return (
<View style={styles.container}>
<Text style={styles.text}>{navigation.getParam("name")}</Text>
</View>
);
}
const styles = StyleSheet.create({
container: {
flex: 1,
alignItems: "center",
alignSelf: "center",
paddingVertical: "100%",
},
text: {
fontSize: 20,
},
});

In your BookScreen, change it to the following:
export default function BookScreen({ navigation, route }) {
const { item } = route.params;
return (
<View style={styles.container}>
<Text style={styles.text}>{item.name}</Text>
</View>
);
}
Edit:
I think you should pass the data like this:
navigation.navigate('Book', {item: item});

render data in FlatList React Native (expo cli) from firebase realtime database?

I'm working on a ToDo app that is connected to the Firebase real-time database. Everything works fine. I can also store data in the Firebase database, but the problem is that I cannot get any data from the database. I want to render data in ScrollView so that the data can be displayed in ScrollView when I open my app.
I'm getting error: ReferenceError: noteArray is not defined <FlatList data={noteArray}
I have uploaded my whole code [codesandbox.io/s/stupefied-snowflake-1lddp?file=/src/App.js][1]
Main.js
import React, { Component } from "react";
import {
StyleSheet,
Text,
View,
TextInput,
TouchableOpacity,
FlatList
} from "react-native";
import Note from "./note";
import firebase from "./firebase";
export default class Main extends React.Component {
constructor(props) {
super(props);
this.state = {
noteArray: [],
noteText: ""
};
}
componentDidMount() {
this.listenForNotes();
}
listenForNotes() {
firebase
.database()
.ref(`todos`)
.on("value", function (snapshot) {
const notes = [];
snapshot.forEach((child) => {
notes.push({
note: child.val().name,
date: child.val().date,
key: child.key
});
});
this.setState({
noteArray: notes
});
});
}
adTask() {
if (this.state.noteText) {
var date = new Date();
var database = firebase.database().ref("todos");
var key = database.push().key;
var todo = {
date:
date.getDay() +
"/" +
(date.getMonth() + 1) +
"/" +
date.getFullYear(),
note: this.state.noteText,
key: key
};
database.child(key).set(todo);
this.setState({ noteText: "" });
}
}
deleteNote(key) {
// your delete note function
}
render() {
return (
<View style={styles.container}>
<View style={styles.header}>
<Text style={styles.headerText}>Todo</Text>
</View>
<FlatList
data={this.state.noteArray}
renderItem={({ item, index }) => {
return (
<Note
key={item.key}
note={item.note}
date={item.date}
deleteMethod={() => this.deleteNote(item.key)}
/>
);
}}
key={(item) => `${item.key}`}
/>
<View style={styles.footer}>
<TextInput
style={styles.textInput}
onChangeText={(noteText) => this.setState({ noteText })}
value={this.state.noteText}
placeholder="Enter Task"
placeholderTextColor="white"
underlineColorAndroid="transparent"
></TextInput>
</View>
<TouchableOpacity
onPress={this.adTask.bind(this)}
style={styles.addButton}
>
<Text style={styles.addButtonText}>Add</Text>
</TouchableOpacity>
</View>
);
}
}
note.js
import React from "react";
import { StyleSheet, Text, View, TouchableOpacity } from "react-native";
export default class Note extends React.Component {
constructor(props) {
super(props);
}
render() {
const { note, date, key, deleteMethod } = this.props;
return (
<View key={key} style={styles.note}>
<Text style={styles.noteText}>{note}</Text>
<Text style={styles.noteDate}>{date}</Text>
<TouchableOpacity onPress={deleteMethod} style={styles.noteDelete}>
<Text style={styles.noteDeleteText}>
<AntDesign name="delete" size={24} color="black" />
</Text>
</TouchableOpacity>
</View>
);
}
}
const styles = StyleSheet.create({
note: {
position: "relative",
padding: 20,
paddingRight: 100,
borderBottomWidth: 2,
borderBottomColor: "#ededed"
},
noteText: {
fontWeight: "bold",
fontSize: 18,
paddingLeft: 20,
borderLeftWidth: 10,
borderLeftColor: "#e91e63"
},
noteDate: {
paddingLeft: 20,
borderLeftWidth: 10,
borderLeftColor: "#e91e63"
},
noteDelete: {
position: "absolute",
justifyContent: "center",
alignItems: "center",
backgroundColor: "#2980b9",
padding: 10,
top: 10,
bottom: 10,
right: 10
},
noteDeleteText: {
color: "white"
}
});
[1]: http://codesandbox.io/s/stupefied-snowflake-1lddp?file=/src/App.js

it should be this.state.noteArray since noteArray is a state variable.
there are couple of errors in the code sandbox
<FlatList
data={noteArray}
renderItem={({ item, index }) => {
should be
<FlatList
data={this.state.noteArray}
renderItem={({ item, index }) => {
and key, should be item.key:
deleteMethod={() => this.deleteNote(key)}
should be
deleteMethod={() => this.deleteNote(item.key)}
this.setState doesn't exist is because you have a function instead of an array function. change it to the following should work:
.on("value", snapshot => {
const notes = [];
snapshot.forEach((child) => {
notes.push({
note: child.val().name,
date: child.val().date,
key: child.key
});
});
this.setState({noteArray: notes});
});

React native app shows an error saying that key will be undefined even after providing a key

In my RN application, I have the following array.
const PDFItems = [
{ id: 1001, name: 'APPLICATION FORM.PDF', size: '2.77 MB' },
{ id: 1002, name: 'BENEFIT ILLUSTRATION.PDF', size: '368 KB' },
{ id: 1003, name: 'PRODUCT SUMMARY.PDF', size: '2.02 MB' },
{ id: 1004, name: 'TERMS AND CONDITIONS.PDF', size: '269 KB' },
];
I created the following function to render items.
renderPDFItems = () => {
return PDFItems.map(item => (
<ListItem
key={item.id.toString()}
icon={<Download />}
title={item.name}
label={item.size}
onPress={() => {}}
/>
));
}
This is my ListItem component.
import React, { Component } from 'react';
import { StyleSheet, TouchableOpacity, View } from 'react-native';
import colors from 'res/colors';
import SinglifeText from './text';
interface IProps {
title: string;
label: string;
icon: Object;
key: string;
onPress?: Function;
}
class ListItem extends Component<IProps> {
render() {
const { title, label, icon, key, onPress } = this.props;
return (
<TouchableOpacity onPress={onPress} key={key}>
<View style={styles.itemContainer}>
<View style={styles.titleContainer}>
<View style={styles.icon}>{icon}</View>
<SinglifeText type={SinglifeText.Types.BUTTON_LBL} label={title} />
</View>
<SinglifeText type={SinglifeText.Types.BODY_SMALL} label={label} />
</View>
</TouchableOpacity>
);
}
}
const styles = StyleSheet.create({
itemContainer: {
borderColor: colors.gray,
borderRadius: 4,
borderWidth: 0.5,
padding: 14,
paddingVertical: 24,
flexDirection: 'row',
alignContent: 'center',
alignItems: 'center',
marginBottom: 10,
},
titleContainer: {
flex: 1,
flexDirection: 'row',
alignContent: 'center',
alignItems: 'center',
},
icon: {
marginRight: 10,
},
});
export default ListItem;
When I run the app, it shows a warning saying that,
key is not a prop. Trying to access it will result in undefined being returned. If you need to access the same value within the child component, you should pass it as a different prop
What am I doing wrong here? My keys are unique and still gives this error.

Just dont name the prop key. Something like id has the same syntactic meaning.
renderPDFItems = () => {
return PDFItems.map(item => (
<ListItem
id={item.id.toString()}
icon={<Download />}
title={item.name}
label={item.size}
onPress={() => {}}
/>
));
}
ListItem.js
class ListItem extends Component<IProps> {
render() {
const { title, label, icon, id, onPress } = this.props;
return (
<TouchableOpacity onPress={onPress} key={id}>
<View style={styles.itemContainer}>
<View style={styles.titleContainer}>
<View style={styles.icon}>{icon}</View>
<SinglifeText type={SinglifeText.Types.BUTTON_LBL} label={title} />
</View>
<SinglifeText type={SinglifeText.Types.BODY_SMALL} label={label} />
</View>
</TouchableOpacity>
);
}
}

It seems your key prop defined is ambiguous to TouchableOpacity key={key}. Try renaming key prop to some other name.

As some guys have said above, we don't need the key prop. TouchableOpacity has the key by default, and we can't use key another prop as 'key'

How to force Flatlist to re-render after getting a single data?

I've faced an issue with flatlist when I get single data from the server and set these into state and passes into data props, I can't see any update in the render "I'm adding some Loading if I'd not received any data I show an let's say Indicator" so the indicator disappears and I see blank screen!!
FYI, When I enable Hot Reloading and just press Save in my IDE I can see the single Data in my Screen!
So how can I force it to appear the data!
Code
import React, { Component } from "react";
import firebase from "react-native-firebase";
import Icon from "react-native-vector-icons/Ionicons";
import _ from "lodash";
import {
View,
Text,
StyleSheet,
FlatList,
TouchableOpacity,
Image,
Dimensions
} from "react-native";
const { width } = Dimensions.get("screen");
class ListChats extends Component {
constructor(props) {
super(props);
this.state = {
users: [],
noChat: true
};
}
_getUsers = () => {
let currentUser = firebase.auth().currentUser.uid;
let ref = firebase.database().ref(`Messages/${currentUser}`);
let usersKeys = [];
ref.once("value").then(snapshot => {
snapshot.forEach(childsnap => {
usersKeys.push(childsnap.key);
});
let usernames = [];
usersKeys.forEach(key => {
firebase
.database()
.ref("users")
.child(key)
.once("value")
.then(usersShot => {
let username = usersShot.val().username;
usernames.push({ username: username, key: key });
});
});
this.setState({ users: usernames,noChat: false });
});
};
componentDidMount() {
this._getUsers();
}
render() {
if (this.state.noChat) {
console.log("IF", this.state.users);
return (
<View style={styles.container}>
<Image
style={{
width,
height: width * 0.7,
resizeMode: "contain"
}}
source={require("../../assets/empty.gif")}
/>
<Text style={{ alignSelf: "center" }}>No Chats Found</Text>
</View>
);
} else {
console.log("Else", this.state.users);
return (
<View style={styles.container}>
<FlatList
key={Math.random() * 1000}
extraData={this.state} // I'm already added
data={this.state.users}
contentContainerStyle={{ flexGrow: 1 }}
renderItem={({ item }) => {
return (
<TouchableOpacity
onPress={() =>
this.props.navigation.navigate("ChatDetails", {
Key: item.key,
userName: item.username
})
}
>
<View style={styles.parent}>
<Icon name="ios-contact" size={50} color="#4d8dd6" />
<View
style={{
flex: 1,
justifyContent: "flex-start",
alignItems: "flex-start",
marginHorizontal: 25
}}
>
<Text
style={{
color: "#000",
fontSize: 17
// marginHorizontal: 25
// alignSelf: "stretch"
}}
>
{item.username}
</Text>
{/* <Text
style={{
color: "#a1a1a1",
marginHorizontal: 35,
marginVertical: 5,
alignSelf: "stretch"
}}
numberOfLines={1}
lineBreakMode="tail"
>
{item.lastMssg.text}
</Text> */}
</View>
<Icon name="ios-chatboxes" size={25} color="#d6d6d6" />
</View>
</TouchableOpacity>
);
}}
keyExtractor={(item, index) => index.toString()}
/>
</View>
);
}
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: "center"
},
parent: {
flexDirection: "row",
justifyContent: "space-between",
alignItems: "center",
paddingVertical: 25,
marginHorizontal: 15,
borderBottomWidth: 1,
borderBottomColor: "#eee"
}
});
export default ListChats;

You have used extra data props but the issue is flatlist does a shallow data comparison so when the length of users changes it won't affect the flatlist so replace it with this.state.users
extraData={this.state.users}
You can see in the documentation it says flatlist is implementation of PureCompoment and PureComponent does a shallow comparison thats the reason it is not re-rendering.
https://reactnative.dev/docs/flatlist#extradata

to force the flatlist re-render. just add a boolean lets say "forceUpdate" to your state and whenever an item is added to flatlist data toggle that boolean and pass that to the extra data of your FlatList instead of the state.