Develop Reference

Giving an error with expo-camera, TypeError: undefined is not an object (evaluating '_expoCamera.CameraType.back')

I'd like help regarding the test code in the expo-camera, I am using expo go and once I run the code, it gives me this error: TypeError: undefined is not an object (evaluating '_expoCamera.CameraType.back'), here is the documentation for the expo-camera: https://docs.expo.dev/versions/latest/sdk/camera/ , I am currently using expocamera 12.3.0 and have used navigation.navigate to navigate to this tab thanks ! and here is the code I directly copied from the site
import { Camera, CameraType } from 'expo-camera';
import { useState } from 'react';
import { Button, StyleSheet, Text, TouchableOpacity, View } from 'react-native';
export default function App() {
const [type, setType] = useState(CameraType.back);
const [permission, requestPermission] = Camera.useCameraPermissions();
if (!permission) {
// Camera permissions are still loading
return <View />;
}
if (!permission.granted) {
// Camera permissions are not granted yet
return (
<View style={styles.container}>
<Text style={{ textAlign: 'center' }}>
We need your permission to show the camera
</Text>
<Button onPress={requestPermission} title="grant permission" />
</View>
);
}
function toggleCameraType() {
setType((current) => (
current === CameraType.back ? CameraType.front : CameraType.back
));
}
return (
<View style={styles.container}>
<Camera style={styles.camera} type={type}>
<View style={styles.buttonContainer}>
<TouchableOpacity
style={styles.button}
onPress={toggleCameraType}>
<Text style={styles.text}>Flip Camera</Text>
</TouchableOpacity>
</View>
</Camera>
</View>
);
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
},
camera: {
flex: 1,
},
buttonContainer: {
flex: 1,
flexDirection: 'row',
backgroundColor: 'transparent',
margin: 64,
},
button: {
flex: 1,
alignSelf: 'flex-end',
alignItems: 'center',
},
text: {
fontSize: 24,
fontWeight: 'bold',
color: 'white',
},
});

Update: fixed it, just changed CameraType.back into Camera.Constants.Type.back, solved

TextBox above Keyboard

I am new to React Native and I have encountered a problem: my TextBox doesn't stay above the keyboard while I am writing in it.
These are the visuals from the application
Screenshot
And this is my Signup.js:
import React, { Component } from 'react';
import {
StyleSheet,
Text,
View,
TouchableOpacity
} from 'react-native';
import Form from '../components/Form';
import Logo2 from'../components/Logo2';
import {Actions} from 'react-native-router-flux';
export default class Signup extends Component {
goBack() {
Actions.pop()
}
render() {
return(
<View style={styles.container}>
<Logo2/>
<Form type="Registrar"/>
<View style={styles.signupTextCont}>
<Text style={styles.signupText}>Ja tens uma conta? </Text>
<TouchableOpacity onPress={this.goBack}><Text style={styles.signupButton}>Entra</Text></TouchableOpacity>
</View>
</View>
)
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#232122'
},
signupTextCont: {
flexGrow: 1,
justifyContent: 'center',
alignItems: 'flex-end',
paddingVertical: 16,
flexDirection: 'row'
},
signupText: {
color: 'rgba(255,255,255,0.7)',
fontSize:16
},
signupButton: {
color: '#FFA200',
fontSize:16,
fontWeight: '500'
}
});
I don't know what I need to code.
Could you please help me?

To replicate my comment that resolved your problem; you can use the component KeyboardAvoidingView from the package react-native. It levels up the area it contains above your virtual keyboard.
Wrap your code like this:
<KeyboardAvoidingView behavior={'position'} enabled>
<View style={styles.signupTextCont}>
<Text style={styles.signupText}>Ja tens uma conta? </Text>
<TouchableOpacity onPress={this.goBack}>
<Text style={styles.signupButton}>Entra</Text>
</TouchableOpacity>
</View>
</KeyboardAvoidingView>
Here's some more info about how it works: https://facebook.github.io/react-native/docs/keyboardavoidingview.

You can wrap your code with KeyboardAvoidingView rather than a normal View so that it can actually lift up any items inside it above the keyboard. You can use <KeyboardAvoidingView behavior="padding">
Hope it helps.

How to make <Text /> as watermark of images in React Native

To make <Text /> as watermark of images, it shows in official Docs:
Background Image via Nesting
A common feature request from developers familiar with the web is background-image. To handle this use case, simply create a normal <Image> component and add whatever children to it you would like to layer on top of it.
return (
<Image source={...}>
<Text>Inside</Text>
</Image>
);
I tried, the "Inside" has white background, not the part of the image.
How to make "Inside" as a watermark of the image? Thanks.

You can use ImageBackground component
Link-> https://reactnative.dev/docs/imagebackground
import React from "react";
import { ImageBackground, StyleSheet, Text, View } from "react-native";
const image = { uri: "https://reactjs.org/logo-og.png" };
const App = () => (
<View style={styles.container}>
<ImageBackground source={image} resizeMode="cover" style={styles.image}>
<Text style={styles.text}>Inside</Text>
</ImageBackground>
</View>
);
const styles = StyleSheet.create({
container: {
flex: 1,
},
image: {
flex: 1,
justifyContent: "center"
},
text: {
color: "white",
fontSize: 42,
lineHeight: 84,
fontWeight: "bold",
textAlign: "center",
backgroundColor: "#000000c0"
}
});
export default App;

JavaScript - Adding an Image : React Native XCode

I am wondering how I would go about inserting an image into this??
I am also wondering whether this is javascript implemented on css or css implemented in javascript?
It was automatically generated by React Native as a default app starter pack and we are just getting to grips with the basics...
import React, {
AppRegistry,
Component,
StyleSheet,
Text,
View
} from 'react-native';
class VLDB extends Component {
render() {
return (
<View style={styles.container}>
<Text style = {styles.welcome}>
VLDB SQL Cheat Sheet!
</Text>
<Text style={styles.welcome}>
Welcome to the SQL Cheat Sheet!
</Text>
<Text style={styles.instructions}>
To get started, edit index.ios.js
</Text>
<Text style={styles.instructions}>
Press Cmd+R to reload,{'\n'}
Cmd+D or shake for dev menu
</Text>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
},
welcome: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
instructions: {
textAlign: 'center',
color: '#333333',
marginBottom: 5,
},
});
AppRegistry.registerComponent('VLDB', () => VLDB);
Cheers, Luke.

To add an image to this, you first need to import in the image component
import React, {
AppRegistry,
Component,
Image,
StyleSheet,
Text,
View
} from 'react-native';
Then you add the image as described in the documentation by either referencing a locally bundled image or a remote image like so...
class VLDB extends Component {
render() {
return (
<View style={styles.container}>
<Image
style={styles.icon}
source={require('./myIcon.png')}
/>
<Image
style={styles.logo}
source={{uri: 'http://facebook.github.io/react/img/logo_og.png'}}
/>
<Text style = {styles.welcome}>
VLDB SQL Cheat Sheet!
</Text>
<Text style={styles.welcome}>
Welcome to the SQL Cheat Sheet!
</Text>
<Text style={styles.instructions}>
To get started, edit index.ios.js
</Text>
<Text style={styles.instructions}>
Press Cmd+R to reload,{'\n'}
Cmd+D or shake for dev menu
</Text>
</View>
);
}
}

How to add a button in React Native?

I´m confused with this whole "no CSS" thing, but I understand why it's beneficial. All I want to do is place a button in the middle of the screen but I don't understand how styling works in React yet. This is my code:
var tapSpeed = React.createClass({
render: function() {
return (
<View style={styles.container}>
<Text style={styles.welcome}>
Tap me as fast as you can!
</Text>
<View style={styles.button}>
!
</View>
</View>
);
}
});
var styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#FFCCCC'
},
welcome: {
fontSize: 20,
textAlign: 'center',
margin: 10
},
button: {
textAlign: 'center',
color: '#ffffff',
marginBottom: 7,
border: 1px solid blue,
borderRadius: 2px
}
});

Update: use built-in Button component.
Deprecated:
Wrap your View into TouchableHighlight for iOS and TouchableNativeFeedback for Android.
var {
Platform,
TouchableHighlight,
TouchableNativeFeedback
} = React;
var tapSpeed = React.createClass({
buttonClicked: function() {
console.log('button clicked');
},
render: function() {
var TouchableElement = TouchableHighlight;
if (Platform.OS === 'android') {
TouchableElement = TouchableNativeFeedback;
}
return (
<View style={styles.container}>
<Text style={styles.welcome}>
Tap me as fast as you can!
</Text>
<TouchableElement
style={styles.button}
onPress={this.buttonClicked.bind(this)}>
<View>
<Text style={styles.buttonText}>Button!</Text>
</View>
</TouchableElement>
</View>
);
}
});

You can use built in react-native Button element.
import React, { Component } from 'react';
import { StyleSheet, View, Button, Alert, AppRegistry } from 'react-native';
class MainApp extends Component {
_onPress() {
Alert.alert('on Press!');
}
render() {
return (
<View style={styles.container}>
<View style={styles.buttonContainer}>
<Button onPress={this._onPress} title="Hello" color="#FFFFFF" accessibilityLabel="Tap on Me"/>
</View>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#FFFFFF'
},
buttonContainer: {
backgroundColor: '#2E9298',
borderRadius: 10,
padding: 10,
shadowColor: '#000000',
shadowOffset: {
width: 0,
height: 3
},
shadowRadius: 10,
shadowOpacity: 0.25
}
})
AppRegistry.registerComponent('MainApp', () => MainApp);
Read More Here.

The react-native-button package provides a button that is styled like a native button. Install it with npm install react-native-button and use it in your component like this:
var Button = require('react-native-button');
var ExampleComponent = React.createClass({
render() {
return (
<Button
style={{borderWidth: 1, borderColor: 'blue'}}
onPress={this._handlePress}>
Press Me!
</Button>
);
},
_handlePress(event) {
console.log('Pressed!');
},
});

You have two options to achieve a touchable component/button to handle user's events.
One is to use the built in Button Component. Check the docs here http://facebook.github.io/react-native/docs/button.html
Two use either TouchableHighlight or TouchableNativeFeedback or TouchableOpacity or TouchableWithoutFeedback. Think of this as a way for you to convert different areas of your app to tappable(clickable) or a way for you to create a custom button.
Each component here is different based on how it behaves once it's tapped by the user. Check the docs for more details. http://facebook.github.io/react-native/docs/touchablewithoutfeedback.html etc.
Concerning styling in react native you will need to understand flexbox layout. Check this css flexbox article all rules are applicable to react-native https://css-tricks.com/snippets/css/a-guide-to-flexbox/ except that you will have to capitalize the rules e.g align-content to alignContent

<Button
onPress={onPressLearnMore}
title="Learn More"
color="#841584"
accessibilityLabel="Learn more about this purple button"
/>

Please check react-native doc's regarding the buttons
You have more than one way to add button in your application and styling it
You can use Button tag and it's have only one way styling by color attribute, it will appearing in IOS different than Android, or by putting button in view tag with style
<View style={style.buttonViewStyle}>
<Button title="Facebook" color="blue" onPress={this.onFacebookPress} />
</View>
And check the TouchableOpacity and TouchableNativeFeedback tags
And take a lock on below link for more options to add custom buttons in your app
https://js.coach/react-native/react-native-action-button?search=button

export default class Login extends React.Component {
barcodeAction = () => {
this.props.navigation.navigate('BarCodeScanner')
}
cleverTapAction = () => {
this.props.navigation.navigate('CleverTapApp')
}
}
render() {
return (
<View style={styles.container}>
<View style={styles.buttonContainer}>
<Button
onPress={this._onPressButton}
title="Press Me"
/>
</View>
<View style={styles.buttonContainer}>
<Button
onPress={this._onPressButton}
title="Press Me"
color="#841584"
/>
</View>
<View style={styles.alternativeLayoutButtonContainer}>
<Button
onPress={this._onPressButton}
title="This looks great!"
/>
<Button
onPress={this._onPressButton}
title="OK!"
color="#841584"
/>
</View>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
},
buttonContainer: {
margin: 20
},
alternativeLayoutButtonContainer: {
margin: 20,
flexDirection: 'row',
justifyContent: 'space-between'
}
});

The Button element from react-native package does not provide built in styling feature. Ex. The "title" props will be in upper case by default. Hence, I've used an another package react-native-elements that provides nice features for Button element along with different styling options.
You can refer more details on Button from react-native-elements

import React, { Component } from 'react';
import { StyleSheet, View, TouchableOpacity, Text} from 'react-native';
var tapSpeed = React.createClass({
render: function() {
return (
<View style={styles.container}>
<TouchableOpacity>
<Text style={styles.welcome}>
Tap me as fast as you can!
</Text>
</TouchableOpacity>
<TouchableOpacity style={styles.button}>
<Text>!</Text>
</TouchableOpacity>
</View>
);
}
});
var styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
flexDirection: 'column',
alignItems: 'center',
backgroundColor: '#FFCCCC'
},
welcome: {
fontSize: 20,
textAlign: 'center',
margin: 10,
alignSelf: 'center'
},
button: {
justifyContent: 'center',
alignItems: 'center',
marginBottom: 7,
border: 1px solid blue,
borderRadius: 2px
}
});