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React Native: Passing useState() data to unrelated screens

Explanation: I am creating a fitness app, my fitness app has a component called WorkoutTimer that connects to the workout screen, and that screen is accessed via the HomeScreen. Inside the WorkoutTimer, I have an exerciseCount useState() that counts every time the timer does a complete loop (onto the next exercise). I have a different screen called StatsScreen which is accessed via the HomeScreen tab that I plan to display (and save) the number of exercises completed.
What I've done: I have quite literally spent all day researching around this, but it seems a bit harder with unrelated screens. I saw I might have to use useContext() but it seemed super difficult. I am fairly new to react native so I am trying my best haha! I have attached the code for each screen I think is needed, and attached a screenshot of my homeScreen tab so you can get a feel of how my application works.
WorkoutTimer.js
import React, { useState, useEffect, useRef } from "react";
import {
StyleSheet,
Text,
View,
TouchableOpacity,
Button,
Animated,
Image,
SafeAreaView,
} from "react-native";
import { CountdownCircleTimer } from "react-native-countdown-circle-timer";
import { Colors } from "../colors/Colors";
export default function WorkoutTimer() {
const [count, setCount] = useState(1);
const [exerciseCount, setExerciseCount] = useState(0);
const [workoutCount, setWorkoutCount] = useState(0);
const exercise = new Array(21);
exercise[1] = require("../assets/FR1.png");
exercise[2] = require("../assets/FR2.png");
exercise[3] = require("../assets/FR3.png");
exercise[4] = require("../assets/FR4.png");
exercise[5] = require("../assets/FR5.png");
exercise[6] = require("../assets/FR6.png");
exercise[7] = require("../assets/FR7.png");
exercise[8] = require("../assets/FR8.png");
exercise[9] = require("../assets/S1.png");
exercise[10] = require("../assets/S2.png");
exercise[11] = require("../assets/S3.png");
exercise[12] = require("../assets/S4.png");
exercise[13] = require("../assets/S5.png");
exercise[14] = require("../assets/S6.png");
exercise[15] = require("../assets/S7.png");
exercise[16] = require("../assets/S8.png");
exercise[17] = require("../assets/S9.png");
exercise[18] = require("../assets/S10.png");
exercise[19] = require("../assets/S11.png");
exercise[20] = require("../assets/S12.png");
exercise[21] = require("../assets/S13.png");
return (
<View style={styles.container}>
<View style={styles.timerCont}>
<CountdownCircleTimer
isPlaying
duration={45}
size={240}
colors={"#7B4FFF"}
onComplete={() => {
setCount((prevState) => prevState + 1);
setExerciseCount((prevState) => prevState + 1);
if (count == 21) {
return [false, 0];
}
return [(true, 1000)]; // repeat animation for one second
}}
>
{({ remainingTime, animatedColor }) => (
<View>
<Image
source={exercise[count]}
style={{
width: 150,
height: 150,
}}
/>
<View style={styles.timeOutside}>
<Animated.Text
style={{
color: animatedColor,
fontSize: 18,
position: "absolute",
marginTop: 67,
marginLeft: 35,
}}
>
{remainingTime}
</Animated.Text>
<Text style={styles.value}>seconds</Text>
</View>
</View>
)}
</CountdownCircleTimer>
</View>
</View>
);
}
const styles = StyleSheet.create({})
WorkoutScreen.js
import React, { useState } from "react";
import { StyleSheet, Text, View } from "react-native";
import WorkoutTimer from "../components/WorkoutTimer";
export default function WorkoutScreen() {
return (
<View style={styles.container}>
<WorkoutTimer />
</View>
);
}
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: "#fff",
alignItems: "center",
justifyContent: "center",
},
});
HomeScreen.js
import React from "react";
import { StyleSheet, Text, View, SafeAreaView, Button } from "react-native";
import { TouchableOpacity } from "react-native-gesture-handler";
import { AntDesign } from "#expo/vector-icons";
import { Colors } from "../colors/Colors";
export default function HomeScreen({ navigation }) {
return (
<SafeAreaView style={styles.container}>
<Text style={styles.pageRef}>SUMMARY</Text>
<Text style={styles.heading}>STRETCH & ROLL</Text>
<View style={styles.content}>
<TouchableOpacity
style={styles.timerDefault}
onPress={() => navigation.navigate("WorkoutScreen")}
>
<Button title="START WORKOUT" color={Colors.primary} />
</TouchableOpacity>
<TouchableOpacity
style={styles.statContainer}
onPress={() => navigation.navigate("StatsScreen")}
>
<AntDesign name="barschart" size={18} color={Colors.primary} />
<Text style={{ color: Colors.primary }}>Statistics</Text>
<AntDesign name="book" size={18} color={Colors.primary} />
</TouchableOpacity>
</View>
</SafeAreaView>
);
}
const styles = StyleSheet.create({})
StatsScreen.js
import React from "react";
import { StyleSheet, Text, View } from "react-native";
import { exerciseCount, workoutCount } from "../components/WorkoutTimer";
export default function StatsScreen() {
return (
<View style={styles.container}>
<Text display={exerciseCount} style={styles.exerciseText}>
{exerciseCount}
</Text>
<Text display={workoutCount} style={styles.workoutText}>
{workoutCount}
</Text>
</View>
);
}
const styles = StyleSheet.create({});
Home Screen Image

As far as I can tell, you're almost there! You're trying to get your 2 state
variables from the WorkoutTimer like this:
import { exerciseCount, workoutCount } from "../components/WorkoutTimer";
Unfortunatly this won't work :( . These two variables change throughout your
App's life-time and that kinda makes them "special".
In React, these kinds of variables need to be declared in a parent component
and passed along to all children, which are interested in them.
So in your current Setup you have a parent child relationship like:
HomeScreen -> WorkoutScreen -> WorkoutTimer.
If you move the variables to HomeScreen (HomeScreen.js)
export default function HomeScreen({ navigation }) {
const [exerciseCount, setExerciseCount] = useState(0);
const [workoutCount, setWorkoutCount] = useState(0);
you can then pass them along to WorkoutScreen or StatsScreen with something
like:
navigation.navigate("WorkoutScreen", { exerciseCount })
navigation.navigate("StatsScreen", { exerciseCount })
You'll probably have to read up on react-navigation's documentation for .navigate I'm not sure I remember this correctly.
In order to read the variable you can then:
export default function WorkoutScreen({ navigation }) {
const exerciseCount = navigation.getParam(exerciseCount);
return (
<View style={styles.container}>
<WorkoutTimer exerciseCount={exerciseCount} />
</View>
);
}
and finally show it in the WorkoutTimer:
export default function WorkoutTimer({ exerciseCount }) {
Of course that's just part of the solution, since you'll also have to pass
along a way to update your variables (setExerciseCount and setWorkoutCount).
I encourage you to read through the links I posted and try to get this to work.
After you've accumulated a few of these stateful variables, you might also want to look at Redux, but this is a bit much for now.
Your app looks cool, keep at it!

I ended up solving this problem with useContext if anyone is curious, it was hard to solve initially. But once I got my head around it, it wasn't too difficult to understand.
I created another file called exerciseContext with this code:
import React, { useState, createContext } from "react";
const ExerciseContext = createContext([{}, () => {}]);
const ExerciseProvider = (props) => {
const [state, setState] = useState(0);
//{ exerciseCount: 0, workoutCount: 0 }
return (
<ExerciseContext.Provider value={[state, setState]}>
{props.children}
</ExerciseContext.Provider>
);
};
export { ExerciseContext, ExerciseProvider };
and in App.js I used ExerciseProvider which allowed me to pass the data over the screens.
if (fontsLoaded) {
return (
<ExerciseProvider>
<NavigationContainer>
<MyTabs />
</NavigationContainer>
</ExerciseProvider>
);
} else {
return (
<AppLoading startAsync={getFonts} onFinish={() => setFontsLoaded(true)} />
);
}
}
I could call it with:
import { ExerciseContext } from "../components/ExerciseContext";
and
const [exerciseCount, setExerciseCount] = useContext(ExerciseContext);
This meant I could change the state too! Boom, solved! If anyone needs an explanation, let me know!

I think you have to use Mobx or Redux for state management. That will be more productive for you instead built-in state.

Pass state from component to Modal?

I have a component and import it in specific screen, in this screen i have a button when clicks i open modal contain component it's a "recorder" so after i record voices i want to take this voice and save them into Parent screen as a state or something!
in the recorder component, I save voices data into state! but how can i pass it to other parent screens!?
so how can I handle it?
here is shots
Parent Screen "after click add voice I show the modal"
Parent Screen
Here's a modal contain a recorder component
Modal
CODE
Component
" I pass data to PassDataToModal state inside componentDidMount "
import React, {Component} from 'react';
import {Platform, StyleSheet, Text, TouchableOpacity, View} from 'react-native';
import {AudioRecorder, AudioUtils} from 'react-native-audio';
import Sound from 'react-native-sound';
import Icon from 'react-native-vector-icons/MaterialIcons';
class RecorderScreen extends Component {
state = {
PassDataToModal: null,
};
componentDidMount() {
AudioRecorder.requestAuthorization().then(isAuthorised => {
this.setState({hasPermission: isAuthorised});
AudioRecorder.onFinished = data => {
console.log('data', JSON.stringify(data));
this.setState({PassDataToModal: data});
};
});
}
render() {
return (
<View style={styles.container}>
<View style={styles.controls}>
{this._renderPlayButton(() => {
this._play();
})}
{this._renderRecordButton(this.state.recording)}
{this._renderStopButton('Stop', () => {
this._stop().then(() => this.setState({currentTime: 0}));
})}
</View>
<Text style={styles.progressText}>{this.state.currentTime}s</Text>
</View>
);
}
}
export default RecorderScreen;
Parent Screen
import Modal from 'react-native-modal';
import RecorderScreen from './Recorder';
class Order extends Component {
constructor(props) {
super(props);
this.state = {
isModalVisible: false,
};
}
toggleModal = () => {
this.setState({isModalVisible: !this.state.isModalVisible});
};
render() {
return (
<View style={styles.container}>
<TouchableOpacity
onPress={this.toggleModal}
>
<Icon name="mic" color="#333" size={20} />
<Text style={{paddingHorizontal: 5}}>Add Voice</Text>
</TouchableOpacity>
<Modal
style={{margin: 0}}
isVisible={this.state.isModalVisible}
>
<View>
<TouchableOpacity onPress={this.toggleModal}>
<Icon name="close" color="#000" size={25} />
</TouchableOpacity>
<RecorderScreen /> // Component
</View>
</View>
)
}
}

In your parent component pass a function to your RecorderScreen component that will send the necessary data up. Docs on lifting state up.
So in your parent you'd have something like:
setData = (data) => {
// Set this to whatever you need it to be named
this.setState({childData: data});
}
Then pass the function as a prop:
<RecorderScreen setData={this.setData} />
And finally, call it in the child however needed (If I'm following the code something like this):
componentDidMount() {
AudioRecorder.requestAuthorization().then(isAuthorised => {
this.setState({hasPermission: isAuthorised});
AudioRecorder.onFinished = data => {
this.props.setData(data);
};
});
}
Then your parent component will have access to the child's data that you have lifted up.

Call component through function React Native

I'm developing a component to publish it in npm, but I'd like to call my component using a method instead of a tag.
Example:
myComponent.js
import React from 'react'
import { View, Text } from 'react-native'
export const showComponent = () => {
// this would be the function that I user to call my component down
}
const myComponent = (props) => {
return(
<View>
<Text>Oi</Text>
</View>
)
}
App.js
import React from 'react'
import { View, Text, TouchableOpacity } from 'react-native'
import { showComponent } from 'my-component'
const App = () => {
return(
<View>
<TouchableOpacity onPress={() => showComponent()}>
<Text>Home</Text>
</TouchableOpacity>
</View>
)
}
export defaul App
the idea is that when calling the showComponent function I show my component, and when I call, for example, the hide function, I close my component.

You can do it using a single class export:
import * as React from 'react';
export default class MyComponent extends React.Component {
state = {
isOpen: false,
};
open = () => {
this.setState({ isOpen: true });
};
close = () => {
this.setState({ isOpen: true });
};
render() {
const { isOpen } = this.state;
return !isOpen ? null : (
<View>
<Text>Oi</Text>
</View>
);
}
}
And you use it like so:
<MyComponent ref={(x) => this.myComponent = x)} />
And you open it like so:
this.myComponent.open();

I see in a comment above you want to call the component with a redux action, so you should call your redux action in that on click, but the component you want to show/hide needs to be linked to a redux state variable. Then in your jsx you'd have:
<View>
<TouchableOpacity onPress={() => showComponent()}>
<Text>Home</Text>
</TouchableOpacity>
{reduxBoolean && <MyComponent />}
</View>

import React from 'react'
import { View, Text} from 'react-native'
const example = (props) => {
return (
<View>
<Text>Hello</Text>
</View>
)
}
// props
import React from 'react'
import { View, Text} from 'react-native'
const examples = () => {
return(
<View>
<Text><example/></Text>
</View>
)
}
and print is : Hello

Getting 'undefined is not an object' when calling navigation prop methods in react native navigation

I'm having trouble calling react navigation methods from custom components outside of my original screens, specifically the one I'm working on right now is trying to call goBack() in a back arrow of a custom header component I made (code below). The error message I'm getting when I click the back arrow is:
undefined is not an object (evaluating '_this2.props.navigation.goBack')
Here is the code:
// HeaderText.js
import React from 'react';
import { View, Text, StyleSheet, TouchableOpacity, Platform } from 'react-native';
import { Icon } from 'expo';
export class HeaderText extends React.Component {
render() {
const needsBackButton = this.props.backIcon;
if (needsBackButton) {
return(
<View style={[styles.headerStyle,styles.buttonHeaderStyle]}>
<TouchableOpacity onPress={() => this.props.navigation.goBack()} style={styles.backButtonStyles}><Icon.Ionicons size={25} style={{ color: '#fff', fontWeight: 'bold' }} name={Platform.OS === 'ios' ? `ios-arrow-back` : 'md-arrow-back'} /></TouchableOpacity>
<Text style={styles.textStyle}>{this.props.headerText}</Text>
<View style={styles.emptyViewStyles} />
</View>
);
} else {
return(
<View style={styles.headerStyle}>
<Text style={styles.textStyle}>{this.props.headerText}</Text>
</View>
);
}
}
}
Here is the screen I'm putting that HeaderText component in:
// SubmitReferralScreen.js
import React from 'react';
import {
Image,
Platform,
ScrollView,
StyleSheet,
Text,
TouchableOpacity,
View,
ImageBackground
} from 'react-native';
import { MonoText } from '../../components/general/StyledText';
import { HeaderText } from '../../components/general/HeaderText';
import { HomeScreenContainer } from '../../components/homeScreen/HomeScreenContainer';
import { IconButton } from '../../components/general/IconButton';
import { StatusInfo } from '../../constants/StatusInfo';
import SvgUri from 'react-native-svg-uri';
export default class SubmitReferralScreen extends React.Component {
static navigationOptions = {
header: null,
};
render() {
return (
<View style={{flex: 1, width: '100%',justifyContent: 'center', alignItems: 'center'}}>
<ImageBackground source={require('../../assets/images/background.png')} style={{width: '100%', height: '100%', flex: 1, justifyContent: 'flex-start', alignItems: 'center', backgroundColor: 'background-color: rgba(0, 0, 0, 0.5)',}}>
<HeaderText backIcon='true' headerText='New Referral' />
<Text>Submit referral here!</Text>
</ImageBackground>
</View>
);
}
}
And here is my Stack Navigator for the referral Screens:
// MainTabNavigator.js
const ReferralStack = createStackNavigator({
Referrals: ReferralScreen,
MakeReferral: SubmitReferralScreen,
});
I've looked at this StackOverflow answer: Getting undefined is not an object evaluating _this.props.navigation
And the answer there was to put only navigation.navigate(YourScreen). I tried that, and the error I got said "cannot find variable navigation".
How can I call navigation props from custom react native components?

By default only screen components are provided with the navigation prop. You can either use library provided ways of hooking up arbitrary components to the navigation state, or you can pass navigation as a prop manually.
Option #1. Using withNavigation:
React navigation exports a higher-order component through which you can inject the navigation props into any component you want. To do this, you can do something like:
Don't immediately export the HeaderText component class (remove export from that line)
At the bottom of that file add export default withNavigation( HeaderText );
or if you don't want to use a default export and keep it as a named export, instead do:
const NavigationConnected = withNavigation( HeaderText );
export { NavigationConnected as HeaderText };
Option #2. Passing navigation as prop: In your SubmitReferralScreen component you can simply pass this.props.navigation as a prop to the HeaderText component like: <HeaderText navigation={ this.props.navigation } />

It's because your navigation prop didn't found where is the navigation's value prop from the parent. Better you make HeaderText component using regular arrow function, like this;
const HeaderText = ({ needsBackButton }) => {
if(needsBackButton) {
return (
<View style={[styles.headerStyle,styles.buttonHeaderStyle]}>
<TouchableOpacity onPress={() => this.props.navigation.goBack()} style={styles.backButtonStyles}><Icon.Ionicons size={25} style={{ color: '#fff', fontWeight: 'bold' }} name={Platform.OS === 'ios' ? `ios-arrow-back` : 'md-arrow-back'} /></TouchableOpacity>
<Text style={styles.textStyle}>{this.props.headerText}</Text>
<View style={styles.emptyViewStyles} />
</View>
)
}
return (
// another component
)
}
And then, You can simply use useNavigation() to access navigation prop from any screen/component.
First, import useNavigation on component that handled function of the moving screen.
import { useNavigation } from '#react-navigation/native';
Create some constant to reference this module:
const navigation = useNavigation()
And then, simply use this on your TouchableOpacity's onPress prop like this;
<TouchableOpacity
onPress={() => navigation.goBack()}
style={styles.backButtonStyles}
>
//...
</ TouchableOpacity>
Get the complete documentation on this:
https://reactnavigation.org/docs/connecting-navigation-prop/

React Native: React-Navigation Cannot read property 'navigate' of undefined

I am currently learning React Native and was having some issue with React-navigation.
What I am trying to do is switch screen when the "button" is being pressed.
In the "button", I have:
onPress={() =>
navigate('Home')}
I have const { navigate } = this.props.navigation; before the return statement.
When I run it, I am getting "Cannot read property 'navigate' of undefined.
I guess it is I have to place this.props.navigation somewhere.
Here are my two files:
"IntroPageFive" is the one that has the button and "react-navigation".
I would like to go to "IntroPageOne" when the button is being clicked.
Code for "IntroPageFive":
import React from 'react';
import { Text, View, Image, Linking, Button, TouchableOpacity } from 'react-native';
import PlaceholderImage from '../images/placeholder_thumbnail.png';
import SignInFooter from './signInFooter';
import { createStackNavigator } from 'react-navigation';
import IntroPageOne from './introPageOne';
const App = createStackNavigator({
Home: { screen: IntroPageOne },
});
class IntroPageFive extends React.Component {
render() {
const {
headerTextStyle,
thumbnailStyle,
viewStyle,
subTextStyle,
mainTextSection,
footerSectionStyle,
startButtonStyle,
startButtonTextStyle,
signInButtonStyle ,
signInButtonTextStyle
} = styles;
const { navigate } = this.props.navigation;
return (
<View style={viewStyle}>
<Image style={thumbnailStyle} source={require('../images/placeholder_thumbnail.png')} />
<View style={mainTextSection}>
<Text style={headerTextStyle}>Take A Ride For</Text>
<Text style={headerTextStyle}>Your Favorite Car!</Text>
</View>
<View>
<TouchableOpacity
onPress={() =>
navigate('Home')
}
style={startButtonStyle}
>
<Text style={startButtonTextStyle}>LET'S GET STARTED</Text>
</TouchableOpacity>
</View>
<View style={footerSectionStyle}>
<SignInFooter />
</View>
</View>
);
}
}
export default IntroPageFive;
Here is the code for "IntroPageOne":
import React from 'react';
import { Text, View, Image, Linking } from 'react-native';
import PlaceholderImage from '../images/placeholder_thumbnail.png';
import SignInFooter from './signInFooter';
const IntroPageOne = () => {
const { headerTextStyle, thumbnailStyle, viewStyle, subTextStyle } = styles;
return (
<View style={viewStyle} >
<Image style={thumbnailStyle} source={require('../images/placeholder_thumbnail.png')} />
<Text style={headerTextStyle}>Forget Everything You</Text>
<Text style={headerTextStyle}>Know About Making</Text>
<Text style={headerTextStyle}>Deals For Your Car</Text>
<Text style={subTextStyle}>Deal negotiation powered by AI</Text>
<SignInFooter />
</View>
);
};
};
export default IntroPageOne;
Could anyone please tell me how to fix this issue?
Thank you.