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React Native - useRef for an array (Expo)

Been using Expo and RN on an app, but I'm stuck with a problem. I'm using Expo Video
to make a photo/video gallery. The problem is, if I have more than 1 video in the array, only the last one will play (problem with useRef). And I couldn't find a way to create a ref for each one of them.
Solutions that I've tried and half worked: I created a VideoComponent (as a function then added on return), and each component had its own useRef and useState for playing inside the component a different useRef/useState for video/status for each. It worked okay-ish. But the problem was when other states changed (user presses like, for example). Whenever a state changes, and rerenders, the whole video reset to the beginning. Which is not ok.
The video reset on state change of other components doesn't affect the video if doing it normally (one useRef/state) but as I said, It's only playing the last component, which is not okay.
import React, { useRef, useState } from 'react';
import {
SafeAreaView,
View,
FlatList,
StyleSheet,
Text,
StatusBar,
} from 'react-native';
function App(props) {
const [allData, setAllData] = useState([
{
medias: [
{ link: 'https://link.com/link1.avi', mediaExtension: 'avi' },
{ link: 'https://link.com/link2.jpg', mediaExtension: 'jpg' },
{ link: 'https://link.com/link3.mov', mediaExtension: 'mov' },
],
name: 'Name',
description: 'description',
},
]);
const video = useRef(null);
const [status, setStatus] = useState({});
return (
<View style={{}}>
<FlatList
horizontal
data={allData}
renderItem={({ item }) => (
<View style={{}}>
{item.medias.map((item) => (
<View>
{item.mediaExtension === 'mov' || 'avi' || 'WebM' ? (
<View style={{ flex: 1 }}>
<TouchableOpacity
onPress={() =>
video.isPlaying
? video.current.pauseAsync()
: video.current.playAsync()
}>
<Video
ref={video}
style={{ alignSelf: 'center' }}
source={{
uri: item.link,
}}
onPlaybackStatusUpdate={(status) =>
setStatus(() => status)
}
/>
</TouchableOpacity>
</View>
) : (
<Image style={{}} source={{ uri: item.link }} />
)}
</View>
))}
</View>
)}
/>
</View>
);
}
export default App;

As far as I understand, you want to create a FlatList of Videos, and onScroll you want to pause it. This can be implemented as shown below
Also, here is a Working Example for this
import * as React from 'react';
import { Text, View, StyleSheet, FlatList } from 'react-native';
import Constants from 'expo-constants';
import VideoPlayer from './components/VideoPlayer';
const Videos = [
{
_id: 1,
source: require('./assets/videoplayback.mp4'),
},
{
_id: 2,
source: require('./assets/videoplayback.mp4'),
},
{
_id: 3,
source: require('./assets/videoplayback.mp4'),
},
{
_id: 4,
source: require('./assets/videoplayback.mp4'),
},
{
_id: 5,
source: require('./assets/videoplayback.mp4'),
},
{
_id: 6,
source: require('./assets/videoplayback.mp4'),
},
];
export default function App() {
const [Viewable, SetViewable] = React.useState([]);
const ref = React.useRef(null);
const onViewRef = React.useRef((viewableItems) => {
let Check = [];
for (var i = 0; i < viewableItems.viewableItems.length; i++) {
Check.push(viewableItems.viewableItems[i].item);
}
SetViewable(Check);
});
const viewConfigRef = React.useRef({ viewAreaCoveragePercentThreshold: 80 });
return (
<View style={styles.container}>
<FlatList
data={Videos}
keyExtractor={(item) => item._id.toString()}
renderItem={({ item }) => <VideoPlayer {...item} viewable={Viewable} />}
ref={ref}
onViewableItemsChanged={onViewRef.current}
viewabilityConfig={viewConfigRef.current}
/>
</View>
);
}
const styles = StyleSheet.create({
container: {
flex: 1,
paddingTop: Constants.statusBarHeight,
backgroundColor: '#ecf0f1',
},
});
and VideoPLayer component looks like this
import * as React from 'react';
import { Text, View, StyleSheet, Dimensions } from 'react-native';
import Constants from 'expo-constants';
import { Video, AVPlaybackStatus } from 'expo-av';
export default function VideoPlayer({ viewable, _id, source }) {
const video = React.useRef(null);
React.useEffect(() => {
if (viewable) {
if (viewable.length) {
if (viewable[0]._id === _id) {
video.current.playAsync();
} else {
video.current.pauseAsync();
}
} else {
video.current.pauseAsync();
}
} else {
video.current.pauseAsync();
}
}, [viewable]);
return (
<View style={styles.container}>
<Video
ref={video}
source={source}
rate={1.0}
volume={1.0}
resizeMode={'contain'}
isLooping
shouldPlay
style={styles.video}
/>
</View>
);
}
const styles = StyleSheet.create({
container: {
width: Dimensions.get('window').width,
marginBottom: 100,
marginTop: 100,
},
video: {
width: Dimensions.get('window').width,
height: 300,
},
});

React native app stuck on white screen without any errors

I am learning React native and was trying to build an app. However, the app is stuck on a white screen and doesn't show anything nor gives any error. This code is going to render a flatlist from an array and will have a delete to swipe button on the right. I am not getting any errors though.
Message.js
import React, { useState } from 'react'
import {
View,
Text,
StyleSheet,
FlatList,
SafeAreaView,
StatusBar,
ItemSeparatorComponent,
Platform
} from 'react-native'
import ListItem from '../components/ListItem'
import ListItemSeparator from '../components/ListItemSeparator'
import DeleteSwipe from '../components/DeleteSwipe'
const messages = [
{
id: 1,
name: 'T1',
description: 'D2',
image: require('../assets/mosh.jpg')
},
{
id: 2,
name: 'T2',
description: 'D2',
image: require('../assets/mosh.jpg')
},
{
id: 3,
name: 'T3',
description: 'D3',
image: require('../assets/mosh.jpg')
},
{
id: 4,
name: 'T4',
description: 'D4',
image: require('../assets/mosh.jpg')
}
]
export default function Message () {
const [messages, setMessage] = useState(messages)
const handleDelete = messages => {
const newMessages = messages.filter(m => m.id != messages.id)
setMessage(newMessages)
}
return (
<SafeAreaView style={styles.screen}>
<FlatList
data={messages}
keyExtractor={messages => messages.id.toString()}
renderItem={({ item }) => (
<ListItem
name={item.name}
description={item.description}
image={item.image}
onPress={() => console.log('touched', item)}
renderRightActions={() => (
<DeleteSwipe onPress={() => handleDelete(item)} />
)}
/>
)}
ItemSeparatorComponent={ListItemSeparator}
/>
<FlatList />
</SafeAreaView>
)
}
const styles = StyleSheet.create({
screen: {
padding: Platform.OS === 'android' ? StatusBar.currentHeight : 0
}
})
DeleteSwipe.js
import React from 'react'
import { View, Text, StyleSheet, TouchableWithoutFeedback } from 'react-native'
import Swipeable from 'react-native-gesture-handler/Swipeable'
import { AntDesign } from '#expo/vector-icons'
const DeleteSwipe = props => {
const { renderRightActions } = props
return (
<TouchableWithoutFeedback onPress={console.log('delete it')}>
<View style={styles.container}>
<AntDesign name='delete' size={24} color='white' />
</View>
</TouchableWithoutFeedback>
)
}
const styles = StyleSheet.create({
container: {
width: 70,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#ff5252'
}
})
export default DeleteSwipe

If it is a debugger issue, Restart the debugger if react native debugger is running. and again start
Or it could be a flexbox issue, Try to add or remove display: flex and flex:1 on this and parent.
Or it could be component is too small, Open inspector from dev menu and check component names in screen.

Change onPress={console.log....} to onPress={() => console.log(...
)}
But it seems what you want is onPress={props.onPress}

When i want to delete one item in my list, everything gets deleted Expo, React Native

This is my app.js
the main body of my app.
...
import React, { useState } from "react";
import {
StyleSheet,
Text,
View,
Button,
TextInput,
FlatList,
} from "react-native";
import GoalItem from "./components/GoalItem";
import GoalInput from "./components/GoalInput";
export default function App() {
const [lifeGoals, setLifeGoals] = useState([]);
const addGoalHandler = (goalTitle) => {
setLifeGoals((currentGoals) => [
...currentGoals,
{ key: Math.random().toString(), value: goalTitle },
]);
};
const removeGoalHandler = (goalId) => {
setLifeGoals((currentGoals) => {
return currentGoals.filter((goal) => goal.id !== goalId);
});
};
return (
<View style={styles.Screen}>
<GoalInput onAddGoal={addGoalHandler} />
<FlatList
keyExtractor={(item, index) => item.id}
data={lifeGoals}
renderItem={(itemData) => (
<GoalItem
id={itemData.item.id}
onDelete={removeGoalHandler}
title={itemData.item.value}
/>
)}
/>
</View>
);
}
const styles = StyleSheet.create({
Screen: {
padding: 50,
},
});
...
This is my GoalItem which houses my list
...
import React from "react";
import { StyleSheet, View, Text, TouchableOpacity } from "react-native";
const GoalItem = (props) => {
return (
<TouchableOpacity onPress={props.onDelete.bind(this, props.id)}>
<View style={styles.ListItem}>
<Text>{props.title}</Text>
</View>
</TouchableOpacity>
);
};
const styles = StyleSheet.create({
ListItem: {
padding: 10,
marginVertical: 10,
backgroundColor: "#CCFFFF",
borderRadius: 15,
},
});
export default GoalItem;
...
This is my GoalInput which handles the userinput and appending onto the list
...
import React, { useState } from "react";
import { View, TextInput, Button, Stylesheet, StyleSheet } from "react-native";
const GoalInput = (props) => {
const [enteredGoal, setEnteredGoal] = useState("");
const InputGoalHandler = (enteredText) => {
setEnteredGoal(enteredText);
};
return (
<View style={styles.inputContainer}>
<TextInput
placeholder="Enter Task Here"
style={styles.InputBox}
onChangeText={InputGoalHandler}
value={enteredGoal}
/>
<Button title="add" onPress={props.onAddGoal.bind(this, enteredGoal)} />
</View>
);
};
const styles = StyleSheet.create({
InputBox: {
borderColor: "black",
borderWidth: 0,
padding: 10,
width: "80%",
},
inputContainer: {
flexDirection: "row",
justifyContent: "space-between",
alignItems: "center",
},
});
export default GoalInput;
...
I believe that the key might be the issue but i'm really not sure. What's supposed to happen is that when you click on an item in the list, it should be deleted, however it's deleting my whole list. How do i solve this?

const removeGoalHandler = (goalId) => {
setLifeGoals(lifeGoals.filter((m) => m.id !== goalId.id));
};
<FlatList
keyExtractor={(item) => item.id}
data={lifeGoals}
renderItem={(itemData) => (
<GoalItem
onDelete={removeGoalHandler}
title={itemData.item.value}
/>
)}
/>
const GoalItem = ({onDelete, title}) => {
return (
<TouchableOpacity onPress={onDelete}>
<View style={styles.ListItem}>
<Text>{title}</Text>
</View>
</TouchableOpacity>
);
};
try this

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.

Add navigation to component onPress (React-Navigation)

In my app I have a FlatList component which renders the component below (effectively a row with small snippets of information), I'd like to have it so that I can click on each component within the FlatList which then takes the user to another screen which provides more details.
I've managed to make it so that each component is clickable and I can make it perform an alert() to show that it is clickable, but using React-Navigation is proving a tad tricky for me to add.
FlatList page:
/* #flow*/
import _ from 'lodash'
import {getAllQuestions} from './questionRepository'
import ProfilePicture from './components/ProfilePicture'
import QuestionerAndQuestion from './questionRow/QuestionerAndQuestion'
import Separator from './components/Separator'
import {Button, FlatList} from 'react-native'
import React, {Component} from 'react'
export default class QuestionList extends Component {
static navigationOptions = ({navigation}) => ({
title: 'AIBU',
headerRight: (
<Button
onPress={_.debounce(() => {
navigation.navigate('Add')
}, 500)}
title="Add"
/>
),
headerStyle: {
backgroundColor: 'rgb(245, 245, 245)',
},
headerLeft: <ProfilePicture size={'small'} />,
})
state = {questions: []}
componentDidMount() {
this.getData()
}
async getData() {
const questions = await getAllQuestions()
this.setState({questions})
}
render() {
return (
<FlatList
ItemSeparatorComponent={Separator}
data={this.state.questions}
renderItem={({item}) => <QuestionerAndQuestion item={item} />}
/>
)
}
}
QuestionerAndQuestion component:
/* #flow */
import ProfilePicture from '../components/ProfilePicture'
import React from 'react'
import TextContainer from './TextContainer'
import {StyleSheet, TouchableWithoutFeedback, View} from 'react-native'
const styles = StyleSheet.create({
row: {
backgroundColor: 'rgb(255, 255, 255)',
height: 125,
flex: 1,
flexDirection: 'row',
},
profilePic: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
flexDirection: 'row',
},
textBody: {
flex: 6,
},
})
const QuestionerAndQuestion = ({item}: {item: Object}) =>
<TouchableWithoutFeedback onPress={() => navigate would go here?}>
<View style={styles.row}>
<View style={styles.profilePic}>
<ProfilePicture />
</View>
<View style={styles.textBody}>
<TextContainer item={item} />
</View>
</View>
</TouchableWithoutFeedback>
export default QuestionerAndQuestion

I assume you navigated to the QuestionList component, therefore, you have the navigation object on there. What you would want to do is pass the navigation down to the QuestionerAndQuestion as a prop and then you can access it from onPress as a prop.
Something like this:
<QuestionerAndQuestion item={item} navigation={this.props.navigation} />
Hope this helps

This solved my issue.
Within QuestionList
render() {
const navigation = this.props.navigation
return (
<FlatList
ItemSeparatorComponent={Separator}
data={this.state.questions}
renderItem={({item}) =>
<QuestionerAndQuestion item={item} onPress={() => navigation.navigate('Question')} />}
/>
)
}
Within QuestionerAndQuestion
const QuestionerAndQuestion = ({item, onPress}: {item: Object, onPress: Object}) =>
<TouchableWithoutFeedback onPress={onPress}>