类型错误：无法读取未定义的展会相机的属性“类型”

Question

我不明白为什么无论我做什么都会收到此错误。我从 barrcodescanner 移动到 expo-camera 并收到此错误

import React, { useState, useEffect } from 'react';
import { Text, View, TouchableOpacity, StyleSheet, Image } from 'react-native';
import { Camera } from 'expo-camera';

export default function CameraComponent() {
const [hasPermission, setHasPermission] = useState(null);
const [cameraRef, setCameraRef] = useState(null);
const [type, setType] = useState(Camera.Constants.Type.back);
const [photo, setPhoto] = useState(null);

useEffect(() => {
    (async () => {
        const { status } = await Camera.requestCameraPermissionsAsync();
        setHasPermission(status === 'granted');
    })();
}, []);

if (hasPermission === null) {
    return <View />;
}
if (hasPermission === false) {
    return <Text>No access to camera</Text>;
}

const takePicture = async () => {
    if (cameraRef) {
        let photo = await cameraRef.takePictureAsync();
        setPhoto(photo.uri);
    }
};

return (
    <View style={styles.container}>
        <Camera style={styles.camera} type={type} ref={ref => setCameraRef(ref)}>
            <View style={styles.buttonContainer}>
                <TouchableOpacity
                    style={styles.button}
                    onPress={() => {
                        setType(
                            type === Camera.Constants.Type.back
                                ? Camera.Constants.Type.front
                                : Camera.Constants.Type.back
                        );
                    }}>
                    <Text style={styles.text}> Flip </Text>
                </TouchableOpacity>
                <TouchableOpacity style={styles.button} onPress={takePicture}>
                    <Text style={styles.text}> Snap </Text>
                </TouchableOpacity>
            </View>
        </Camera>
        {photo && (
            <View style={styles.previewContainer}>
                <Text style={styles.previewText}>Preview:</Text>
                <Image source={{ uri: photo }} style={styles.previewImage} />
            </View>
        )}
    </View>
);

}

>const [type, setType] = useState(Camera.Constants.Type.back); 

Unresolved variable Constants
Same error heres
>type === Camera.Constants.Type.back
        ? Camera.Constants.Type.front
        : Camera.Constants.Type.back

我真的不明白哪里出了问题，也不知道从哪里开始。

或者我收到“无法读取‘类型’未定义的属性”错误

Answer 1

该错误是由相机切换“setType”设置引起的。使用 expo-camera 时，您需要使用此代码来更改相机切换：

function toggleCameraFacing() {
setFacing(current => (current === 'back' ? 'front' : 'back'));}

return (
   <View style={styles.container}>
     <CameraView style={styles.camera} facing={facing}>
       <View style={styles.buttonContainer}>
         <TouchableOpacity style={styles.button} onPress= 
            {toggleCameraFacing}>
            <Text style={styles.text}>Flip Camera</Text>
         </TouchableOpacity>
       </View>
     </CameraView>
   </View>
);

来源： expo-camera