text: import React from 'react';
  import { View, StyleSheet, ActivityIndicator } from 'react-native';
  import firebase from 'firebase';
  
  class Loading extends React.Component {
      componentDidMount() {
          firebase.auth().onAuthStateChanged(user => {
              if (user) {
              this.props.navigation.navigate('App');
              } else {
              this.props.navigation.navigate('SignUp');
              }
          });
      }
      render() {
          return (
          <View style={styles.container}>
              <ActivityIndicator size="large" />
          </View>
          );
      }
  }
  const styles = StyleSheet.create({
      container: {
          flex: 1,
          alignItems: 'center',
          justifyContent: 'center'
      }
  });
  export default Loading;