Profile
The profile screen displays the user's avatar, name, and a Logout button for signing out:
import React, { PropTypes } from 'react'
import { View, Image, Button, Text } from 'react-native'
import { observer, inject } from 'mobx-react/native'
import Icon from 'react-native-vector-icons/FontAwesome'
import notifications from '../notifications'
@inject('users') @observer
class Profile extends React.Component {
  static navigationOptions = {
    tabBarLabel: 'Profile',
    tabBarIcon: ({ tintColor }) => (
      <Icon name="user" size={30} color={tintColor}/>
    ),
  };
  imgPlaceholder = 
  'https://cdn.pixabay.com/photo/2017/03/21/02/00/user-
                    2160923_960_720.png'
  onPressLogout() {
    this.props.users.logout();
  }
  render () {
    return (
        <View style={{ padding: 20 }}>
          {
              this.props.users.name &&
              <View style={{ flexDirection: 'row', alignItems: 'center' 
          }}>
            ...