App.js

import React, {Component} from 'react'
import { Text, InputText, View, StyleSheet, Dimensions } from 'react-native'

const {width, height} = Dimensions.get('window')

export default class App extends Component {
  render(){
    <View style={styles.container}>
      <InputText
        style={styles.inputText}
      />
      <ListView 
        style={styles.listView}
      />
    </View>
  }
}

const styles = StyleSheet({
  inputText: {
    height: 30,
    width: width,
    borderWidth: 1,
    borderColor: '#cecece'
  },
  listView: {
    flex: 1,
  },
  container: {
    flex: 1
  }
})