index.android_SLB.js

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

export default class SectionListBasics extends Component {
  render() {
    return (
      <View style={styles.container}>
        <SectionList
          /*sections={[
            {title: 'D', data: [{key:'Devin'}]},
            {title: 'J', data: [{key:'Jackson'}, {key:'James'}, {key:'Jillian'}, {key:'Jimmy'}, {key:'Joel'},{key: 'John'}, {key:'Julie'}]},
          ]}*/ // the key is needed or an warning is shown research keyextracter
          sections={[
            {title: 'D', data: ['Devin']},
            {title: 'J', data: ['Jackson', 'James', 'Jillian', 'Jimmy', 'Joel', 'John', 'Julie']},
          ]}
          renderItem={({item}) => <Text style={styles.item}>{item}</Text>}
          renderSectionHeader={({section}) => <Text style={styles.sectionHeader}>{section.title}</Text>}
        />
      </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,
  },
})

// skip this line if using Create React Native App
AppRegistry.registerComponent('AwesomeProject', () => SectionListBasics);