Duvida sobre react native

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow
 */

import React, {Fragment} from 'react';
import { Component} from 'react';
import {
  SafeAreaView,
  StyleSheet,
  ScrollView,
  View,
  Image,
  Alert,
  Button,
  Text,
  TextInput,
  StatusBar,
} from 'react-native';

import {
  Colors,
  DebugInstructions,
  ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';

export default class App extends Component{
constructor(){
  super();
  this.state = {value: ''};
}
ButtonCall = () =>{
  const {value} = this.state;
  Alert.alert
  
  ("Imprimindo..."); 
  
}
render() {
  return (
    <Fragment>
      <StatusBar barStyle="dark-content" />
      <SafeAreaView>
        <ScrollView
          contentInsetAdjustmentBehavior="automatic"
          style={styles.scrollView}>
          {global.HermesInternal == null ? null : (
            <View style={styles.engine}>
              <Text style={styles.footer}>Engine: Hermes</Text>
            </View>
          )}
          <View style={styles.body}>
            <View style={styles.scrollView}>
            <Image
         style={styles.logoPolishop}
         source={require('./polishop.jpg')}/>
            </View>
           <View style={styles.sectionContainer}>
             <TextInput 
             
             style={{height: 250, fontSize: 20, marginTop: 150}}
             placeholder="Digite aqui seu texto para imprimir"
             onChangeText={ (value) => this.setState({value}) 
             

          }
             />
             <Text style={{marginTop: 0}}>________________________________________________________________________</Text>
           <View>
           <Button
           onPress={this.ButtonCall}
           title = "Imprimir"
           />
           
           </View>
           </View>
          </View>
        </ScrollView>
      </SafeAreaView>
    </Fragment>
  );
};

}
const styles = StyleSheet.create({
  scrollView: {
    backgroundColor: '#ff0000',
  },
  engine: {
    position: 'absolute',
    right: 0,
  },
  body: {
    backgroundColor: '#ffffff', 
  },
  sectionContainer: {
    marginTop: 32,
    paddingHorizontal: 24,
  },

logoPolishop:{
  marginTop: -40,
  width: 340,
  right: -50,
  height: 70,
},

  sectionTitle: {
    fontSize: 24,
    fontWeight: '600',
    color: Colors.black,
  },
  sectionDescription: {
    marginTop: 8,
    fontSize: 18,
    fontWeight: '400',
    color: Colors.dark,
  },
  highlight: {
    fontWeight: '700',
  },
  footer: {
    color: Colors.dark,
    fontSize: 12,
    fontWeight: '600',
    padding: 4,
    paddingRight: 12,
    textAlign: 'right',
  },
});