How to get this.setState to work in React-Native - node.js

Question

I am struggling to get this.setState to work with react-native. I keep getting this.setState is not a function error. I am using an arrow function, which i thought would use the enclosing scope and there was no need to bind to this. But it is not working as expected. I appreciate any help i can get.
**
* Sample React Native App
* https://github.com/facebook/react-native
*
* #format
* #flow strict-local
*/
import React from 'react';
import {
SafeAreaView,
StyleSheet,
ScrollView,
View,
Text,
StatusBar,
Button,
} from 'react-native';
import {
Header,
LearnMoreLinks,
Colors,
DebugInstructions,
ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';
const App: () => React$Node = () => {
state = {
textValue: 'Original Text'
};
buttonPress = () => this.setState({textValue: 'New Text'})
return (
<>
<StatusBar barStyle="dark-content" />
<SafeAreaView>
<ScrollView
contentInsetAdjustmentBehavior="automatic"
style={styles.scrollView}>
<Header />
{global.HermesInternal == null ? null : (
<View style={styles.engine}>
<Text style={styles.footer}>Engine: Hermes</Text>
</View>
)}
<View style={styles.body}>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>{this.state.textValue}</Text>
<Button
onPress={buttonPress}
title="Learn More"
color="#841584"
accessibilityLabel="This is a button"
/>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Step One</Text>
<Text style={styles.sectionDescription}>
Edit <Text style={styles.highlight}>App.js</Text> to change this
screen and then come back to see your edits.
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>See Your Changes</Text>
<Text style={styles.sectionDescription}>
<ReloadInstructions />
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Debug</Text>
<Text style={styles.sectionDescription}>
<DebugInstructions />
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Learn More</Text>
<Text style={styles.sectionDescription}>
Read the docs to discover what to do next:
</Text>
</View>
<LearnMoreLinks />
</View>
</ScrollView>
</SafeAreaView>
</>
);
};
const styles = StyleSheet.create({
scrollView: {
backgroundColor: Colors.lighter,
},
engine: {
position: 'absolute',
right: 0,
},
body: {
backgroundColor: Colors.white,
},
sectionContainer: {
marginTop: 32,
paddingHorizontal: 24,
},
sectionTitle: {
fontSize: 24,
fontWeight: '600',
color: Colors.black,
},
sectionDescription: {
marginTop: 8,
fontSize: 18,
fontWeight: '400',
color: Colors.dark,
},
highlight: {
fontWeight: '700',
},
footer: {
color: Colors.dark,
fontSize: 12,
fontWeight: '600',
padding: 4,
paddingRight: 12,
textAlign: 'right',
},
});
export default App;

Answer 1

Use react hooks
import React, { useState } from 'react'
const App: () => React$Node = () => {
const [textValue, setTextValue] = useState('Original Text')
buttonPress = () => setTextValue('New Text')
...
}

Answer 2

If you want to use the setState feature, class definition is required. Like this.
class App extends React.Component {
constructer(props) {
super(props)
this.state = {
textValue: 'Original Text'
};
}
buttonPress = () => this.setState({textValue: 'New Text'})
render () {
return (
...
)
}
}
If you want to use the function, please read the document.
https://reactjs.org/docs/hooks-intro.html