我试图在登录和注册之间进行简单的导航，但是我得到了“TypeError：undefined 不是评估‘_this2.props.navigation.navigate’的对象”。我不太明白为什么。

下面的代码：

SwitchNavigator.js

import React from 'react'
import { createSwitchNavigator, createAppContainer } from 'react-navigation';
import Login from '../screens/Login'
import Signup from '../screens/Signup'
import Profile from "../screens/Profile";

const SwitchNavigator = createSwitchNavigator(
  {
      Login: {
          screen: Login
      },
      Signup: {
          screen: Signup
      },
      Profile: {
          screen: Profile
      }
  },
  {
      initialRouteName: 'Login'
  }
)

export default createAppContainer(SwitchNavigator)

Login.js

import React from 'react'
import {View, Text, StyleSheet, TouchableOpacity, TextInput, Button} from 'react-native'

class Login extends React.Component {
    state = {
        email: '',
        password: ''
    }

    render() {
        return (
            <View style={styles.container}>
                <Text style={styles.jungleText}>Jungle</Text>
                <TextInput
                    style={styles.inputBox}
                    value={this.state.email}
                    onChangeText={email => this.setState({ email })}
                    placeholder='Email'
                    autoCapitalize='none'
                />
                <TextInput
                  style={styles.inputBox}
                  value={this.state.password}
                  onChangeText={password => this.setState({ password })}
                  placeholder='Password'
                  secureTextEntry={true}
                />
                <TouchableOpacity style={styles.button}>
                    <Text style={styles.buttonText}>Login</Text>
                </TouchableOpacity>
              <Button
                title="Don't have an account yet? Sign up"
                onPress={() => this.props.navigation.navigate('Signup')}
              />
            </View>
        )
    }
}

export default Login

非常感谢你的帮助！