Javascript 字体未在IOS或Android上加载

上面说我可以使用Expo.Apploading，但我对此一无所知。如果有人能帮忙，那就太好了。这在我正在运行的任何一台设备中都会发生。下面是App.js的代码

import React, {useState}from 'react';
import {Text, View } from 'react-native';
import *as Font from 'expo-font';
import {AppLoading} from 'expo';

import {enableScreens} from 'react-native-screens';
import EstesGuideNavigator from './navigation/EstesGuideNavigator'; 

enableScreens(); // useScreens has been changed to enableScreens - this helps screens load faster in background

const fetchFonts = () => {   //fetching costum fonts for my app using Async
  Font.loadAsync({
    'raleway-blackItalic' : require('./assets/fonts/Raleway-BlackItalic.ttf'),
    'raleway-bold' : require('./assets/fonts/Raleway-Bold.ttf'),
    'raleway-regular' : require('./assets/fonts/Raleway-Regular.ttf'),
    'raleway-thin' : require('./assets/fonts/Raleway-Thin.ttf')
  });
}; 

export default function App()  {

const [fontLoaded, setFontLoaded] = useState(false); //initially it's false because app hasn't been loaded 

if (!fontLoaded) {
  return(
  <AppLoading 
  startAsync = {fetchFonts} 
  onFinish = {() => setFontLoaded(true) }
  /> //if assets(fonts here) is not loaded we display loading screen and load assets for app
  );  

} 
return <EstesGuideNavigator/>;

}

import React，{useState}来自“React”；
从“react native”导入{Text，View}；
从“expo字体”导入*作为字体；
从“expo”导入{AppLoading}；
从“react native screens”导入{enableScreens}；
从“/navigation/EstesGuideNavigator”导入estsguidenavigator；
启用屏幕（）；//UseScreences已更改为enableScreens-这有助于在后台更快地加载屏幕
const fetchFonts=（）=>{//使用异步为我的应用程序获取costum字体
Font.loadAsync({
“raleway blackItalic”：要求（“./assets/fonts/raleway blackItalic.ttf”），
“raleway bold”：要求（“./assets/font/raleway bold.ttf”），
“raleway regular”：要求（“./assets/font/raleway regular.ttf”），
“raleway thin”：需要（“./assets/fonts/raleway thin.ttf”）
});
}; 
导出默认函数App（）{
const[fontLoaded，setFontLoaded]=useState（false）；//最初为false，因为应用程序尚未加载
如果（！fontLoaded）{
返回(
我不知道哪里出了问题，但这就是我处理字体加载的方式，效果非常好

import { AppLoading } from "expo";
import { Asset } from "expo-asset";
import * as Font from "expo-font";
import React, { useState } from "react";
import { Platform, StatusBar, StyleSheet, View } from "react-native";
import { Ionicons } from "@expo/vector-icons";

import AppNavigator from "./navigation/AppNavigator";

export default function App(props) {
  const [isLoadingComplete, setLoadingComplete] = useState(false);

  if (!isLoadingComplete && !props.skipLoadingScreen) {
    return (
      <AppLoading
        startAsync={loadResourcesAsync}
        onError={handleLoadingError}
        onFinish={() => handleFinishLoading(setLoadingComplete)}
      />
    );
  } else {
    return (
      <View style={styles.container}>
        {Platform.OS === "ios" && <StatusBar barStyle="default" />}
        <AppNavigator />
      </View>
    );
  }
}

async function loadResourcesAsync() {
  await Promise.all([
    Asset.loadAsync([
      require("./assets/images/tick.png"),
      require("./assets/images/error.png")
    ]),
    Font.loadAsync({
      // This is the font that we are using for our tab bar
      ...Ionicons.font,
      // We include SpaceMono because we use it in HomeScreen.js. Feel free to
      // remove this if you are not using it in your app
      "space-mono": require("./assets/fonts/SpaceMono-Regular.ttf"),
      "Gilroy-Bold": require("./assets/fonts/Gilroy-Bold.otf"),
      "Gilroy-Medium": require("./assets/fonts/Gilroy-Medium.otf"),
      "Gilroy-Heavy": require("./assets/fonts/Gilroy-Heavy.otf")
    })
  ]);
}

function handleLoadingError(error) {
  // In this case, you might want to report the error to your error reporting
  // service, for example Sentry
  console.warn(error);
}

function handleFinishLoading(setLoadingComplete) {
  setLoadingComplete(true);
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: "#fff"
  }
});

从“expo”导入{AppLoading}；
从“expo资产”导入{Asset}；
从“expo字体”导入*作为字体；
从“React”导入React，{useState}；
从“react native”导入{平台、状态栏、样式表、视图}；
从“@expo/vector icons”导入{Ionicons}”；
从“/navigation/AppNavigator”导入AppNavigator；
导出默认功能应用程序（道具）{
const[isLoadingComplete，setLoadingComplete]=useState（false）；
如果（！isLoadingComplete&&！props.skipLoadingScreen）{
返回(
handleFinishLoading（setLoadingComplete）}
/>
);
}否则{
返回(
{Platform.OS===“ios”&&}
);
}
}
异步函数loadResourcesAsync（）{
等待承诺([
Asset.loadAsync([
要求（“./assets/images/tick.png”），
要求（“./assets/images/error.png”）
]),
Font.loadAsync({
//这是我们用于选项卡栏的字体
…Ionicons.font，
//我们包括SpaceMono，因为我们在HomeScreen.js中使用它
//如果未在应用程序中使用，请将其删除
“space mono”：要求（“./assets/fonts/SpaceMono Regular.ttf”），
“Gilroy Bold”：要求（“./assets/font/Gilroy Bold.otf”），
“Gilroy Medium”：要求（“./assets/font/Gilroy Medium.otf”），
“Gilroy Heavy”：要求（“/assets/font/Gilroy Heavy.otf”）
})
]);
}
函数handleLoadingError（错误）{
//在这种情况下，您可能希望将错误报告给您的错误报告
//服务，例如哨兵
控制台。警告（错误）；
}
功能手柄完成加载（设置加载完成）{
设置加载完成（真）；
}
const styles=StyleSheet.create({
容器：{
弹性：1，
背景颜色：“fff”
}
});