React Native：undefined不是一个对象（评估'_this2.props.navigation.navigate'）

Question

我是React Native的新手。反应本机错误：

  

未定义不是对象（正在评估'_this2.props.navigation.navigate'）

我在登录页面上遇到此错误以浏览注册页面。

login.js

   import React, { Component } from 'react';
   import { StatusBar, Dimensions, View, Text, TouchableOpacity, 
   ImageBackground, Image, TextInput } from 'react-native';
   import Icon from 'react-native-vector-icons/FontAwesome5'
   import LinearGradient from "react-native-linear-gradient";
    import { Item, Input } from 'native-base';
   import { widthPercentageToDP as wp, heightPercentageToDP as hp } from 
   'react-native-responsive-screen';
   var { height, width } = Dimensions.get("window")

    export default class Login extends Component {
    constructor(props) {
  super(props);
    this.state = {
    username: null,
     password: null
   };
 }
 v
 render() {

return 
    <View style={{ flexDirection: "row", justifyContent: 'center', alignItems: 'center', marginTop: 15 }}>
      <Text style={styles.hesabınText}>Hesabın yok mu? </Text>
      <TouchableOpacity onPress={() => {
        this.props.navigation.navigate('Register')
      }} >
        <Text style={{ fontFamily: "Montserrat-Bold", fontSize: 15, color: "#6DA942" }}> Kayıt Ol!
          </Text>
      </TouchableOpacity>
    </View>
</View>;
 }
 }

还有我的index.js代码；

          import { AppRegistry } from 'react-native';
      import App from './Bottom/App'
      import {createStackNavigator} from 'react-navigation'
      import Login from './screen/Login';
      import register from './screen/Register';
      console.disableYellowBox = true;

      const stack = createStackNavigator({
        Login: {
          screen: Login,
          navigationOptions: ({ navigation }) => ({
            header: null,
            gestureEnabled: null
          })
        },
        Register: {
          screen: register,
          navigationOptions: ({ navigation }) => ({
            header: null,
            gestureEnabled: null
          })
        },

      });
      AppRegistry.registerComponent('unirehberi', () =>  hesap );

我想在页面之间切换。我该怎么办或出现此问题的原因是什么？