title: [[ERROR]] undefined is not an object(evaluating '_this2.props.navigation.push')
body: <p>Guys I'm with this problem and I can't solve it, I try many things but this error apears to me. So I'm lost, please help me </p>
  
  <p>this in the main ( Route) : App.js    </p>
  
  <pre><code>const Router = createStackNavigator(
    {
      Login: {screen: LoginScreen},
      Julia: {screen: JuliaScreen},
    },
    {
      initialRouteName: 'Login',
      headerMode: 'none',
    }
  )
  </code></pre>
  
  <p>LoginScreen.js --> The Login Screen</p>
  
  <pre><code>          &lt;View style = {styles.formContainer}&gt;
  
                &lt;LoginForm/&gt;
  
            &lt;/View&gt;
  </code></pre>
  
  <p>LoginForm.js --> Component of Login ( Login Form )</p>
  
  <pre><code>import React, { Component } from 'react';
  import {  View, Text, StyleSheet, TextInput, TouchableOpacity, StatusBar, AsyncStorage } from 'react-native';
  
  
  import JuliaScreen from './JuliaScreen'
  
      export default class LoginForm extends Component {
        render() {
          return (
  
            &lt;View style = {styles.container}&gt;
  
              &lt;StatusBar 
                barStyle = "light-content" 
              /&gt;
  
              &lt;TextInput 
  
                  onChangeText = {(username) =&gt; this.setState({username})}
                  value = {this.state.username}
              /&gt;
              &lt;TextInput 
  
                  ref = {(input) =&gt; this.passwordInput = input}
                  onChangeText = {(password) =&gt; this.setState({password})}
                  value = {this.state.password}
              /&gt;
  
              &lt;TouchableOpacity onPress = {  () =&gt; {this.props.navigation.push('Julia')} } style = {styles.btnContainer}&gt;
                  &lt;Text style = {styles.btnText}&gt;LOGIN&lt;/Text&gt;
              &lt;/TouchableOpacity&gt;    
            &lt;/View&gt;
          );
        }
  </code></pre>