App.js

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

export default class App extends Component {
  render() {
    return (
      <View style={styles.container}>
        <SectionList
            sections={[
                {title: 'A', data: ['Adanson']},
                {title: 'J', data:['John', 'Joseph', 'Jojo', 'Jimmy', 'Joel']},
            ]}
            renderItem={({item}) => <Text style={styles.item}>{item}</Text>}
            renderSectionHeader={({section}) => <Text style={styles.sectionHeader}>{section.title}</Text>}
            keyExtractor={(item, index) => index}
        />
      </View>
    );
  }
}

const styles = StyleSheet.create({
    container: {
        flex: 1,
        paddingTop: 22
    },
    sectionHeader: {
        paddingTop: 2,
        paddingLeft: 10,
        paddingRight: 10,
        paddingBottom: 2,
        fontSize: 14,
        fontWeight: 'bold',
        backgroundColor: 'rgba(247,247,247,1.0)',
    },
    item: {
        padding: 10,
        fontSize: 18,
        height: 44,
    },
})

AppRegistry.registerComponent('react-native-tutorial', () => App);