<TextInput
          textContentType="password"
          autoCapitalize="none"
          secureTextEntry={true}
          value={this.state.password}
          underlineColorAndroid="transparent"
        />

import React, {Component} from 'react';
    import {Modal, Text, TouchableHighlight, View, Alert} from
    'react-native';

    class ModalExample extends Component {
     state = {
    modalVisible: false,
        };

     setModalVisible(visible) {
     this.setState({modalVisible: visible});
      }

      render() {
        return (
         <View style={{marginTop: 22}}>
           <Modal
            animationType="slide"
            transparent={false}
            visible={this.state.modalVisible}
            onRequestClose={() => {
            Alert.alert('Modal has been closed.');
          }}>
          <View style={{marginTop: 22}}>
            <View>
              <TextInput
                 textContentType="password"
                 autoCapitalize="none"
                 secureTextEntry={true}
                 value={this.state.password}
                 underlineColorAndroid="transparent"
              />
            </View>
          </View>
        </Modal>

        <TouchableHighlight
          onPress={() => {
            this.setModalVisible(true);
          }}>
          <Text>Show Modal</Text>
        </TouchableHighlight>
      </View>
    ); }}