Button.js

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

export default class ButtonBasics extends Component {
  _onPressButton() {
    var time = new Date().getTime();
    var code = "challenge_code_" + time;
    fetch('https://pk88u3qgl2.execute-api.us-east-1.amazonaws.com/test/v1/example/', {
      method: 'POST',
      headers: {
        'Accept': 'application/json',
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        code: code,
        name: 'challenge description at time ' + time,
      })
    })
    alert('Thanks! Challenge submitted. Waiting for someone to accept.')
  }

  render() {
    return (
      <View style={styles.container}>
        <View style={styles.buttonContainer}>
          <Button
            onPress={this._onPressButton}
            title="Send a Friendly Challenge"
          />
        </View>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
   flex: 1,
   justifyContent: 'center',
  },
  buttonContainer: {
    margin: 20
  },
  alternativeLayoutButtonContainer: {
    margin: 20,
    flexDirection: 'row',
    justifyContent: 'space-between'
  }
});