App.js

import React, { Component } from 'react'

import { Root } from 'native-base'

import AppNavigator from './AppNavigator'

export default class App extends Component<{}> {

 navStack = []

 constructor (props) {
 super(props)
 this.pushNavStack = this.pushNavStack.bind(this)
 this.popNavStack = this.popNavStack.bind(this)
 this.isExitable = this.isExitable.bind(this)
 }

 componentDidMount () {
 // SplashScreen.hide();
 }

 pushNavStack (screen) {
 this.navStack.push(screen)
 }

 popNavStack () {
 this.navStack.pop()
 }

 isExitable () {
 if (this.navStack.length == 1) {
 return true
 } else {
 return false
 }
 }

 render () {
 return (
 <Root>
 <AppNavigator
 screenProps={{pushNavStack: this.pushNavStack, popNavStack: this.popNavStack, isExitable: this.isExitable}}/>
 </Root>
 )
 }
}