无法读取未定义的属性“后面”

Question

我正在开发一个 React Native 应用程序，该应用程序使用 expo-camera 拍摄 id 的照片以供用户完成入门，但我不断收到错误“渲染错误，无法读取未定义的属性‘后面’”。 51世博会可能有问题吗？

这是我的代码。

import { CameraView, CameraType, useCameraPermissions } from "expo-camera";
import { useState } from "react";
import { Button, StyleSheet, Text, TouchableOpacity, View } from "react-native";

export default function CameraApp() {
  const [facing, setFacing] = useState(CameraType.back);
  const [permission, requestPermission] = useCameraPermissions();

  if (!permission) {
    // Camera permissions are still loading.
    return <View />;
  }

  if (!permission.granted) {
    // Camera permissions are not granted yet.
    return (
      <View style={styles.container}>
        <Text style={styles.message}>
          We need your permission to show the camera
        </Text>
        <Button onPress={requestPermission} title="grant permission" />
      </View>
    );
  }

  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>
  );
}

"expo": "~51.0.20",
"expo-camera": "^15.0.14",

Answer 1

事实证明，expo-camera 与 typescript 配合使用效果最佳。下面的代码运行没有错误。

import { CameraView, CameraType, useCameraPermissions } from 'expo-camera';
import { useState } from 'react';
import { Button, StyleSheet, Text, TouchableOpacity, View } from 'react-native';

export default function Camera() {
  const [facing, setFacing] = useState<CameraType>('back');
  const [permission, requestPermission] = useCameraPermissions();

  if (!permission) {
    // Camera permissions are still loading.
    return <View />;
  }

  if (!permission.granted) {
    // Camera permissions are not granted yet.
    return (
      <View style={styles.container}>
        <Text style={styles.message}>We need your permission to show the camera</Text>
        <Button onPress={requestPermission} title="grant permission" />
      </View>
    );
  }

  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>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
  },
  message: {
    textAlign: 'center',
    paddingBottom: 10,
  },
  camera: {
    flex: 1,
  },
  buttonContainer: {
    flex: 1,
    flexDirection: 'row',
    backgroundColor: 'transparent',
    margin: 64,
  },
  button: {
    flex: 1,
    alignSelf: 'flex-end',
    alignItems: 'center',
  },
  text: {
    fontSize: 24,
    fontWeight: 'bold',
    color: 'white',
  },
});