React Native-10：活动指示器loading

import React, { useState, useEffect } from 'react'
import
{
    StyleSheet, Text, View, Button,
    ActivityIndicator  // 活动指示器 loading
} from 'react-native'

const App = () =>
{

    const [animation, setAnimation] = useState(true)

    useEffect(() =>
    {
        closeActivityIndicator()
        return () =>
        {

        }
    }, [])
    let closeActivityIndicator = () =>
    {
        setAnimation(!animation)
    }
    return (
        <View style={styles.container}>
            <Text style={styles.text}>羽神天下第一</Text>
            {/* 活动指示器 切换 animation 属性进行显示隐藏切换 */}
            <ActivityIndicator style={styles.activityIndicator} color="pink" size="large" animating={animation} />
            <Button onPress={closeActivityIndicator} title='切换显示loading'></Button>
        </View>
    )
}

export default App

const styles = StyleSheet.create({
    container: {
        flex: 1,
        marginTop: 70
    },
    text: {
        color: 'pink',
        textAlign: 'center',
        fontSize: 24
    },
    activityIndicator: {
        height: 80
    }
})