无法在reactnative中添加边框底部

我正在做一份登记表.

我创建了一个名为Regform的文件.组件目录下的js.

我无法获取文本注册的边界底部

这里是演示链接demo working link

请让我知道，我做错了什么

组件/注册表.js

import * as React from 'react';  

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


 export default class Regform extends React.Component {  
  render() {  
   return (  
    <View>  
     <Text style={styles.header}> Registration </Text> 

      <TextInput style = {styles.textinput}
      underlineColorAndroid = "transparent"
      placeholder = "Enter Your Name"
      placeholderTextColor = "#9a73ef"
      onChangeText = {this.handleName}/>

      <TextInput style = {styles.textinput}
      underlineColorAndroid = "transparent"
      placeholder = "Enter Your Email"
      placeholderTextColor = "#9a73ef"
      autoCapitalize = "none"
      onChangeText = {this.handleEmail}/>

    </View>  
   );  
  }  
 } 


 const styles = StyleSheet.create({  

      header: {  
        fontSize: 36,
        alignself: 'self',
        color: 'red',
        marginBottom: 30,
        borderBottomColor: 'red',
        borderBottomWidth: 2
      },
      textinput: {
        fontSize: 18,
        alignself: 'self',
        color: 'black',
        marginBottom: 30,
        borderBottomColor: 'grey',
        borderBottomWidth: 2
      }
  });