可以使用下面的notifyMessage来显示吐司消息：

import {
      ToastAndroid,
      Platform,
      AlertIOS,
    } from 'react-native';

function notifyMessage(msg: string) {
  if (Platform.OS === 'android') {
    ToastAndroid.show(msg, ToastAndroid.SHORT)
  } else {
    AlertIOS.alert(msg);
  }
}

或
在iOS和Android中使用react-native-simple-toast。

import Toast from 'react-native-simple-toast';

Toast.show('This is a toast.');
Toast.show('This is a long toast.', Toast.LONG);

React Native现在有内置的API Alert，可以在iOS和Android上运行。https://reactnative.dev/docs/alert

为这个定制的吐司创建一个单独的组件，并在其中使用以下代码：

import React, {
     useState, 
    useImperativeHandle,
     forwardRef,
     useRef } from "react";
import {
      Text,
      StyleSheet,
      Animated,
      Platform,
      UIManager,
    } from "react-native";
    
    if (
      Platform.OS === "android" &&
      UIManager.setLayoutAnimationEnabledExperimental
    ) {
      UIManager.setLayoutAnimationEnabledExperimental(true);
    }
    
    const Toast = (props, ref) => {
      const [showToast, setShowToast] = useState(false);
      const fadeAnim = useRef(new Animated.Value(0)).current;
    
      const toast = () => {
        if (!showToast) {
          setShowToast(true);
          Animated.timing(fadeAnim, {
            toValue: 1,
            duration:500,
            useNativeDriver: true,
          }).start();
          setTimeout(() => {
            Animated.timing(fadeAnim, {
              toValue: 0,
              duration: 500,
              useNativeDriver: true,
            }).start(() => {
              setShowToast(false);
            });
          }, 3000); 
        }
      };
    
      useImperativeHandle(ref, () => ({
        toast,
      }));
    
      if (showToast) {
        return (
          <Animated.View style={[styles.toastContainer, { opacity: fadeAnim }]}>
            <Text style={styles.toastText}>{props.message}</Text>
          </Animated.View>
        );
      } else {
        return null;
      }
    };
    
    const styles = StyleSheet.create({
      container: {
        position: "absolute",
        borderRadius: 30,
        overflow: "hidden",
        flexDirection: "row",
        bottom: 20,
        right: 20,
        alignItems: "center",
        justifyContent: "center",
      },
      toastContainer: {
        backgroundColor: "#292929",
        borderRadius: 10,
        padding: 10,
        position: "absolute",
        bottom: 100,
        alignSelf: "center",
      },
      toastText: {
        color: "white",
        fontSize: 14,
      },
    });
    
    export default forwardRef(Toast);

并从所需的组件调用它;供您参考：

const ToastRef = useRef(null);
     const showToast = () => {
        ToastRef.current.toast();
      };

    <Toast ref={ToastRef} message="Hello World!" />

如果你正在寻找一个简单的，JS唯一的实现吐司通知的React Native，它可以在iOS和Android上工作，你可以看看
https://github.com/jeanverster/react-native-styled-toast
用途：

import { useToast } from 'react-native-styled-toast'

const { toast } = useToast()

return <Button onPress={() => toast({ message: 'Check me out!', ...config })} />

您也可以使用包吐司消息。检查react-native-toast-message