Develop Reference

expo/google fonts Does not work outside App.js

I am a newbie. I'm making a YouTube Clone using React-Native.In my project I'm trying to use custom google fonts via expo/google and I'm following their example. I installed "balsamiq-sans" font using npx expo install #expo-google-fonts/balsamiq-sans. Imported in App.js and it works ! BUT, when I try to use it in Header.js (component) it does not work. The fonts does not change.
Here's what I'v done-
App.js file
import { StyleSheet, Text, View } from 'react-native';
import Home from './src/screens/Home'
import AppLoading from 'expo-app-loading';
import { useFonts, BalsamiqSans_400Regular } from '#expo-google-fonts/balsamiq-sans';
export default function App() {
let [fontsLoaded] = useFonts({
BalsamiqSans_400Regular,
});
if (!fontsLoaded) {
return <AppLoading />;
} else {
return (
<View>
<Home />
<Text style={{fontFamily: "BalsamiqSans_400Regular"}}> This Works ! </Text>
</View>
);
}
}
Home.js
import { StyleSheet, Text, View } from 'react-native';
import Header from '../components/Header';
export default function Home() {
return (
<View >
<Header />
</View>
);
}
And finally, Header.js
import { StyleSheet, Text, View } from 'react-native';
import {Entypo} from "#expo/vector-icons"
import { Ionicons } from '#expo/vector-icons';
import Constant from 'expo-constants'
export default function Header() {
return (
<View style={{
paddingTop:Constant.statusBarHeight,
height: 80,
backgroundColor: "white",
flexDirection: "row",
alignItems: "center",
justifyContent: "space-between",
elevation: 5
}}>
<View style={{
flexDirection: "row",
margin: 5,
padding: 5,
alignItems: "center"
}}>
<Entypo style={{
marginLeft: 20
}} name='youtube' size={24} color="red" />
<Text style={{
fontSize: 19,
marginLeft: 10,
fontWeight: "bold",
fontFamily: "BalsamiqSans_400Regular"
}}>Does not work</Text> // this does not work
</View>
<View style={{
flexDirection: "row"
}} >
<Ionicons name="ios-search-circle" size={27} color="black" />
<Ionicons style={{marginRight: 20, marginLeft: 20}} name="ios-sunny-sharp" size={25} color="black" />
</View>
</View>
)
}
Any ideas? what am I doing wrong. And sorry for bad English.
Edit: Fonts change in web but does not change in my Android emulator and in my Android Phone(using Expo Go)

move this to header component
import { useFonts, BalsamiqSans_400Regular } from '#expo-google-fonts/balsamiq-sans';
export default function Header() {
let [fontsLoaded] = useFonts({
BalsamiqSans_400Regular,
});
if (!fontsLoaded) {
return <AppLoading />;
} else {
then read this docs to know what formats work on which platforms:

Can someone help me with a React Navigation screen change problem?

I'm having a problem getting my React Navigation to actually transition screens. I've used it successfully before and I cannot figure out what my problem is this time. I click my button and no transition happens. I think it might be a problem with the inline onPress not running....does it have to be in Main Button? Or does the inline code on App.js override anything in MainButton.js.
Also...NarScreen is the screen I'm trying to get to.
FILE 1: App.js
import 'react-native-gesture-handler';
import React from 'react';
import { View, Text, StyleSheet, Image } from 'react-native';
import { NavigationContainer } from '#react-navigation/native';
import { createStackNavigator } from '#react-navigation/stack';
import { color } from 'react-native-reanimated';
import MainButton from './components/MainButton';
import NarScreen from './screens/NarScreen.js'
function HomeScreen({ navigation }) {
return(
<View style={styles.background}>
<View style={styles.logo}>
<Image source={require('./components/HNS1.png')} style={styles.image} resizeMode='contain' />
</View>
<View style={styles.buttons}>
<MainButton onPress={() => navigation.navigate('Nar')}>NAR Test</MainButton>
<MainButton>Tripoli Test</MainButton>
</View>
</View>
);
}
function Nar({ navigation }) {
return(
<NarScreen />
)
}
const Stack = createStackNavigator();
function App() {
return(
<NavigationContainer>
<Stack.Navigator>
<Stack.Screen name="Home" component={HomeScreen} />
<Stack.Screen name="Nar" component={Nar} />
</Stack.Navigator>
</NavigationContainer>
);
}
const styles = StyleSheet.create({
background: {
backgroundColor: '#00629B',
flex: 1,
},
buttons: {
marginTop: "20%",
marginLeft: 10,
},
image: {
width: '80%',
height: 300,
borderRadius: 20,
},
logo: {
borderRadius: 200,
marginTop: '30%',
alignItems: 'center'
},
});
export default App;
File 2: NarScreen.js
import React from 'react';
import { View, Text, Button, StyleSheet } from 'react-native';
const NarScreen = props => {
return(
<View>
<Text>BigScreen!</Text>
</View>
)
}
export default NarScreen;
FILE 3: MainButton.js
import React from 'react';
import {View, Text, StyleSheet, TouchableOpacity, } from 'react-native';
const MainButton = props => {
return <TouchableOpacity>
<View style={styles.button}>
<Text style={styles.buttonText}>{props.children}</Text>
</View>
</TouchableOpacity>
}
const styles = StyleSheet.create({
button: {
backgroundColor: "#FCD757",
paddingVertical: 30,
paddingHorizontal: 30,
height: 100,
width: 300,
marginTop: "10%",
borderRadius: 10,
marginLeft: '12%',
justifyContent: 'space-between',
},
buttonText: {
color: 'black',
fontSize: 26,
textAlign: 'center',
}
})
export default MainButton;

Inside your MainButton.js file, you are not handling onPress event. Add it to touchable opacity.
const MainButton = props => {
return <TouchableOpacity onPress={props.onPress}>
<View style={styles.button}>
<Text style={styles.buttonText}>{props.children}</Text>
</View>
</TouchableOpacity>
}

Rendering another screen in react-native app

I'm experiencing trouble navigating between pages in my react native app. When I attempt to use the button, I get the following error message: TypeError: undefined is not an object (evaluating '_this.props.navigation') I have created my app using numerous js files, and id like to navigate between them using buttons. My App.js file renders to the WelcomeScreen from initializing.
import 'react-native-gesture-handler';
import React from 'react';
import { NavigationContainer } from '#react-navigation/native';
import RecipesList from "cakeapp/app/screens/RecipesList.js";
import { ImageBackground, StyleSheet, View, Text, Button, navigation } from "react-native";
function WelcomeScreen(props) {
return (
<NavigationContainer>
<ImageBackground
style={styles.background}
source={require('cakeapp/app/assets/MainPage.png')}
>
<Text style={styles.text}>MyCakeRecipes</Text>
<View style={styles.homeButton}>
<Button
title="Recipes"
onPress={() => this.props.navigation.navigate('RecipesList')}
/>
</View>
</ImageBackground>
</NavigationContainer>
);
}
const styles = StyleSheet.create({
background: {
flex:1,
justifyContent: "flex-end",
},
text: {
fontSize: 30,
fontWeight: "bold",
color: "white",
textAlign: "center",
bottom: 500,
},
homeButton: {
width: '100%',
height: 40,
backgroundColor: '#5f7f8a'
}
})
export default WelcomeScreen;
import React from 'react';
import { Image, ScrollView, View, Text, } from 'react-native';
const imageDis = {
width: 150,
height: 150
//flex:1,
//justifyContent: "flex-end"
};
const Recipes = () => (
<ScrollView style={{backgroundColor: '#5f7f8a'}}>
<Text style={{ fontSize: 20 }}>Chocolate Cake</Text>
<Image source={require('cakeapp/app/assets/Choc.png')} style={imageDis} />
<Text style={{ fontSize: 20 }}>Chocolate cupcake</Text>
<Image source={require('cakeapp/app/assets/ChocCu.png')} style={imageDis} />
<Text style={{ fontSize: 20 }}>Lemon Cake</Text>
<Image source={require('cakeapp/app/assets/Lemon.png')} style={imageDis} />
<Text style={{ fontSize: 20 }}>Lemom meringue</Text>
<Image source={require('cakeapp/app/assets/LemonM.png')} style={imageDis} />
<Text style={{ fontSize: 20 }}>Chocolate Berry</Text>
<Image source={require('cakeapp/app/assets/ChcoBerry.png')} style={imageDis} />
</ScrollView>
);
export default Recipes

As far as I know, < NavigationContainer> is used in app.js file to define the screens you want to navigate to. And you have to pass navigation as a prop to the component.
Your app.js file should look something like this
const Stack = createStackNavigator();
const App = () => {
return (
<NavigationContainer>
<Stack.Navigator>
<Stack.Screen
name="Welcome"
component={WelcomeScreen}
/>
<Stack.Screen
name="Recipes"
component={RecipesList} />
</Stack.Navigator>
</NavigationContainer>
);
};
And your welcomeScreen like this:
const WelcomeScreen = ({ navigation }) => {
return (
<Button
title="RecipesList"
onPress={() =>
navigation.navigate('RecipesList')
}
/>
);
};
Let me know if it doesnt work

React Native: How does this Component call?

Can someone help me with this Component, i want to make like this, but dont know how this white frames called? Can someone tell me this? And if we press that yellow Touchable Opacity it is showing whole Text, and if we press again it will became smaller!
Thanks in Advance , I am Just new in RN

You can easily create that card with a little bit of CSS.
Below is the sample app which shows you how you can achieve that.
Working Example: Expo Snack
import React, { useState, useEffect } from 'react';
import {
Text,
View,
StyleSheet,
FlatList,
Image,
TouchableOpacity,
} from 'react-native';
import { AntDesign } from '#expo/vector-icons';
import Constants from 'expo-constants';
import { newsFeed } from './news';
export default function App() {
const [news, setNews] = useState(newsFeed);
const showFull = (index) => {
const temp = [...news];
temp[index].toggle = !temp[index].toggle;
setNews(temp);
};
return (
<View style={styles.container}>
<FlatList
data={news}
renderItem={({ item, index }) => (
<View style={styles.card}>
<Text style={styles.title}>{item.title}</Text>
<Text style={styles.paragraph}>
{item.toggle ? item.desc : `${item.desc.substr(0, 100)}...`}
</Text>
{item.toggle && (
<Image source={{ uri: item.img }} style={styles.img} />
)}
<View style={styles.bottomBar}>
<Text style={styles.date}>4/02/2021</Text>
<TouchableOpacity onPress={() => showFull(index)}>
<View style={{ flexDirection: 'row', alignItems: 'center' }}>
<Text style={styles.moreBtn}>
{!item.toggle ? 'More' : 'Less'}
</Text>
<AntDesign
name={item.toggle ? 'up' : 'down'}
size={12}
color="orange"
/>
</View>
</TouchableOpacity>
</View>
</View>
)}
/>
</View>
);
}
const styles = StyleSheet.create({
bottomBar: {
marginVertical: 5,
flexDirection: 'row',
justifyContent: 'space-between',
},
container: {
flex: 1,
justifyContent: 'center',
paddingTop: Constants.statusBarHeight,
backgroundColor: '#ecf0f1',
padding: 8,
},
card: {
padding: 10,
backgroundColor: 'white',
marginVertical: 5,
borderRadius: 10,
},
title: {
marginVertical: 5,
fontSize: 18,
fontWeight: 'bold',
},
img: {
flex: 1,
height: 100,
borderRadius: 10,
marginVertical: 5,
},
paragraph: {
fontSize: 14,
},
date: {
fontSize: 12,
color: 'rgba(21,21,21,0.5)',
},
moreBtn: {
fontSize: 12,
color: 'orange',
marginRight: 10,
},
});

actually this card is not a component you can design it using css and if you want to create a component which you can reuse then you can make one component and reuse it as you want and for this card either you can use your own css or a library called native-base which is
like bootstrap but it is used in react-native
you can read about native base here for more information
https://nativebase.io/
and if you want to create card of your own then make a separate file and make a funcional card component in it
and call it wherever you like
import myCustomCard from './card'
and to use it you use like this in your jsx
<myCustomCard />
and if you want to know more about how to pass props and else you can checkout official docs of the react native here
https://reactnative.dev/docs/getting-started

Invariant Violation: Element type is invalid: React Native

I started to learning react native a 4-5 days ago and now I am building a login screen in React Native. But facing this issue, I am trying to figure it out but unfortunately, I couldn't do so. Can guys please help me? I am attaching my code and screenshot Here.Error Screenshot
App.js
import React, { Component} from 'react';
import { StyleSheet, Text, View } from 'react-native';
import Login from './src/screens/Login';
export default class App extends Component {
render() {
return (
<Login />
);
}
}
Here is the Login screen code
Login.js
import React, { Component} from 'react';
import { StyleSheet, TextInput, View, Image, StatusBar, Dimensions } from 'react-native';
import { LinearGradient } from 'expo';
import EStyleSheet from 'react-native-extended-stylesheet';
import { Button } from '../components/Button';
import { Ionicons } from '#expo/vector-icons';
const {width: WIDTH} = Dimensions.get('window')
EStyleSheet.build();
export default class Login extends Component {
render() {
return (
<LinearGradient
colors={['#38E870', '#2BB256']}
style={styles.container}>
<StatusBar barStyle="light-content" />
<View style={styles.logocontainer}>
<Image source={require('../images/Devastic.png/')} />
</View>
<View style={styles.formContainer}>
<View style={styles.inputcontainer}>
<Ionicons name="ios-person-outline" size={36} color="#747475"
style={styles.inputemail}/>
<TextInput
placeholder={'Enter Your Email'}
underlineColorAndroid={'transparent'}
placeholderTextColor="#dfe6e9"
style={styles.input}
/>
<Ionicons name="ios-unlock-outline" size={34} color="#747475"
style={styles.inputpass}/>
<TextInput
placeholder={'Enter Your Password'}
secureTextEntry={true}
underlineColorAndroid={'transparent'}
placeholderTextColor="#dfe6e9"
style={styles.input}
/>
<Button
text="Log In"
onPress={() => console.log ("Pressed")}
/>
</View>
</View>
</LinearGradient>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
alignItems: 'center',
},
logocontainer: {
paddingTop: 50,
},
formContainer: {
backgroundColor: '#FFF',
marginTop: 180,
width: 360,
height: 340,
borderRadius: 10,
shadowColor: '#000',
shadowOffset: { width: 0, height: 2 },
shadowOpacity: 0.6,
shadowRadius: 6,
elevation: 8,
},
inputcontainer: {
marginTop: 30,
},
inputemail: {
position: 'absolute',
left: 18,
top: 13,
},
inputpass: {
position: 'absolute',
left: 18,
top: 77,
},
input: {
width: WIDTH -50 ,
height: 44,
padding: 10,
paddingLeft: 40,
marginVertical: 10,
marginHorizontal: 10,
borderWidth: 1,
borderRadius: 20,
borderColor: 'black',
marginBottom: 10,
}
});
here is the Button.js File code
import React from 'react';
import { View, TouchableHighlight, TouchableNativeFeedback, Text, Platform } from 'react-native';
import EStyleSheet from 'react-native-extended-stylesheet';
const styles = EStyleSheet.create({
$buttonColor: '#38E870',
$buttonTextColor: '#ffffff',
$buttonUnderlayColor: '#2BB256',
button: {
backgroundColor: '$buttonColor',
paddingVertical: 10,
paddingHorizontal: 30,
marginHorizontal: 12,
borderRadius: 40,
marginTop: 20,
},
text: {
color: '$buttonTextColor',
fontSize: 18,
textAlign: 'center',
fontWeight: 'bold',
},
});
export const Button = ({ text, onPress }) => {
if (Platform.OS === 'ios') {
return (
<TouchableHighlight
onPress={onPress}
style={styles.button}
underlayColor={styles.$buttonUnderlayColor}
>
<Text style={styles.text}>{text}</Text>
</TouchableHighlight>
);
}
return (
<TouchableNativeFeedback
onPress={onPress}
background={TouchableNativeFeedback.Ripple(styles.$buttonUnderlayColor)}
>
<View style={styles.button}>
<Text style={styles.text}>{text}</Text>
</View>
</TouchableNativeFeedback>
);
};

In your Login.js file, you are importing Button as object.
Change as following:
From
import { Button } from '../components/Button';
To
import Button from '../components/Button';
For more information, please have a look : Uncaught Error: Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function but got: object
Hope this will help !

I think the issue because the way you have exported the Button component.
export foo;
import {foo} from 'blah';
export default foo;
import foo from 'blah';
solution to your problem
Replace this
export const Button = ({ text, onPress }) =>
with this
export default const Button = ({ text, onPress }) =>
for more detail check this more detail