import React, { useEffect } from "react";
import { Text, View, StyleSheet, BackHandler, Alert } from "react-native";
import { useBackHandler } from "@react-native-community/hooks"

const App = () => {

  // Callback function for back action
  const backActionHandler = () => {
    Alert.alert("Alert!", "Are you sure you want to exit app?", [
      {
        text: "Cancel",
        onPress: () => null,
        style: "cancel"
      },
      { text: "YES", onPress: () => BackHandler.exitApp() }
    ]);
    return true;
  };

  // hook which handles event listeners under the hood
  useBackHandler(backActionHandler)

  return (
    <View style={styles.container}>
      <Text style={styles.text}>Click Back button!</Text>
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    alignItems: "center",
    justifyContent: "center"
  },
  text: {
    fontSize: 18,
    fontWeight: "bold"
  }
});

export default App;