如何在反应本机博览会应用程序（android）中授予相机权限

Question

我的代码是：

import React, { useEffect } from "react";
import * as ImagePicker from "expo-image-picker";

import Screen from "./app/components/Screen";

export default function App() {
  async function permisionFunction() {
    const result = await ImagePicker.getCameraPermissionsAsync();
    if (!result.granted) {
      console.log(result);
      alert("need access to gallery for this app to work");
    }
  }

  useEffect(() => {
    permisionFunction();
  }, []);

  return <Screen></Screen>;
}

第一次提示时我拒绝了相机的权限。 现在，每当我打开应用程序时，总是need access to gallery for this app to work 会显示此消息。安卓版。

• 我尝试在设置中将所有权限授予 expo 应用程序，但仍然出现相同的消息。 我该如何解决这个问题。

Answer 1

我有同样的问题...我正在使用 expo SDK 42，并且在拒绝回答后权限请求不再触发。

无论如何，你的代码有一些错误，你必须注意权限响应的状态属性。

这是检查响应状态的方法

const requestPermissions = async () => {
    try {
      const {
        status,
      } = await ImagePicker.requestMediaLibraryPermissionsAsync();
      console.log('status lib', status);
      setHasPickerPermission(status === 'granted');
    } catch (error) {
      console.log('error', error);
    }
    try {
      const { status } = await ImagePicker.requestCameraPermissionsAsync();
      console.log('status camera', status);
      setHasCameraPermission(status === 'granted');
    } catch (error) {
      console.log('error', error);
    }
  };

  useEffect(() => {
    requestPermissions();
  }, []);

Answer 2

使用expo-cameramodule 访问设备摄像头。

我策划了一个小应用程序的工作示例，您可以使用它访问图库和设备相机中的图片。

工作应用：Expo Snack

import React, { useState, useEffect } from 'react';
import { StyleSheet, Text, View, Button, Image } from 'react-native';
import { Camera } from 'expo-camera';
import * as ImagePicker from 'expo-image-picker';

export default function Add({ navigation }) {
  const [cameraPermission, setCameraPermission] = useState(null);
  const [galleryPermission, setGalleryPermission] = useState(null);

  const [camera, setCamera] = useState(null);
  const [imageUri, setImageUri] = useState(null);
  const [type, setType] = useState(Camera.Constants.Type.back);

  const permisionFunction = async () => {
    // here is how you can get the camera permission
    const cameraPermission = await Camera.requestPermissionsAsync();

    setCameraPermission(cameraPermission.status === 'granted');

    const imagePermission = await ImagePicker.getMediaLibraryPermissionsAsync();
    console.log(imagePermission.status);

    setGalleryPermission(imagePermission.status === 'granted');

    if (
      imagePermission.status !== 'granted' &&
      cameraPermission.status !== 'granted'
    ) {
      alert('Permission for media access needed.');
    }
  };

  useEffect(() => {
    permisionFunction();
  }, []);

  const takePicture = async () => {
    if (camera) {
      const data = await camera.takePictureAsync(null);
      console.log(data.uri);
      setImageUri(data.uri);
    }
  };

  const pickImage = async () => {
    let result = await ImagePicker.launchImageLibraryAsync({
      mediaTypes: ImagePicker.MediaTypeOptions.Images,
      allowsEditing: true,
      aspect: [1, 1],
      quality: 1,
    });

    console.log(result);
    if (!result.cancelled) {
      setImageUri(result.uri);
    }
  };

  return (
    <View style={styles.container}>
      <View style={styles.cameraContainer}>
        <Camera
          ref={(ref) => setCamera(ref)}
          style={styles.fixedRatio}
          type={type}
          ratio={'1:1'}
        />
      </View>

      <Button title={'Take Picture'} onPress={takePicture} />
      <Button title={'Gallery'} onPress={pickImage} />
      {imageUri && <Image source={{ uri: imageUri }} style={{ flex: 1 }} />}
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  cameraContainer: {
    flex: 1,
    flexDirection: 'row',
  },
  fixedRatio: {
    flex: 1,
    aspectRatio: 1,
  },
  button: {
    flex: 0.1,
    padding: 10,
    alignSelf: 'flex-end',
    alignItems: 'center',
  },
});

Answer 3

doc 配置中有提及。

在托管应用中，相机需要Permissions.CAMERA。视频录制需要Permissions.AUDIO_RECORDING。