React Native Map Region Persistency - Save and Restore the last region on the map set by your user

MapScreen.js

import React from 'react'
import { View, StyleSheet, AsyncStorage } from 'react-native'
import MapView from 'react-native-maps'

const DEFAULT_REGION = {
	latitude: 32.068185,
	longitude: 34.778051,
	latitudeDelta: 0.045,
	longitudeDelta: 0.045,
}

const STORAGE_REGION_KEY = 'nester.map.region'

_getValue = async (key) => {
	try {
		value = await AsyncStorage.getItem(key)
		return JSON.parse(value)
	} catch (error) {
		console.log('Error retrieving data: '+error)
		throw error
	}
}

_saveValue = async (key, value) => {
	try {
		await AsyncStorage.setItem(key, JSON.stringify(value))
		return value
	} catch (error) {
		console.log(error)
		throw error
	}
}

_removeValue = async (key) => {
	try {
		await AsyncStorage.removeItem(key)
		return true
	} catch (error) {
		console.log(error)
		throw error
	}
}

class MapScreen extends React.Component {

	constructor(props) {
		super(props)
		this.state = {
			region: DEFAULT_REGION
		}
	}

	async _initialRegion() {
		region = await _getValue(STORAGE_REGION_KEY)
		return region || DEFAULT_REGION
	}

	_onRegionChangeComplete = (region) => {
		_saveValue(STORAGE_REGION_KEY, region)
	}

	componentDidMount() {
		this._initialRegion().then(region => {
			this.setState({region: region})
		})
	}


	render() {
		return (
			<View style={styles.container}>
			<MapView
				style={styles.map}
				region={this.state.region}
				onRegionChangeComplete={this._onRegionChangeComplete}>
			</MapView>
			</View>
		)
	}
}

const styles = StyleSheet.create({
	container: {
		flex: 1,
		backgroundColor: 'black'
	},
	map: {
		position: 'absolute',
		top: 0,
		left: 0,
		right: 0,
		bottom: 0,
	},
})

export default MapScreen

MapScreen is a React Native component which implements a full screen map using react-native-maps by Airbnb.
It saves (to local storage) the last active map region (or viewport if you prefer) and restores it back whenever its being mounted.
Having consistent map region between app launches improves user experience not needing to pan and zoom the map again and again.