app.js

import React, { Component } from 'react';
import {
  StyleSheet,
  Text,
  View
} from 'react-native';

import {RadioGroup, RadioButton} from 'react-native-flexi-radio-button'

class App extends Component{

    constructor(){
        super()
        this.state = {
            text: ''
        }
        this.onSelect = this.onSelect.bind(this)
    }

    onSelect(index, value){
        this.setState({
        text: `Selected index: ${index} , value: ${value}`
        })
    }

    render(){
        return(
            <View style={styles.container}>
                <RadioGroup
                    onSelect = {(index, value) => this.onSelect(index, value)}
                >
                    <RadioButton value={'item1'} >
                        <Text>This is item #1</Text>
                    </RadioButton>

                    <RadioButton value={'item2'}>
                        <Text>This is item #2</Text>
                    </RadioButton>

                    <RadioButton value={'item3'}>
                        <Text>This is item #3</Text>
                    </RadioButton>

                </RadioGroup>
                
                <Text style={styles.text}>{this.state.text}</Text>
            </View>
        )
    }
}

let styles = StyleSheet.create({
    container: {
        marginTop: 40,
        padding: 20
    },
    text: {
        padding: 10,
        fontSize: 14,
    },
})

module.exports = App