在React Native相机中，camera.takePictureAsync(options)不是一个函数。

Question

你好，我是React Native的新手，正在尝试使用摄像头构建自己的第一个React Native项目并且没有使用expo。我使用 npm install react-native-camera 安装了它，然后用 react-native link react-native-camera 进行了链接。

摄像头初始化成功，但是当我触发快照按钮时，会出现以下错误...

{ [TypeError: camera.takePictureAsync is not a function. (In 'camera.takePictureAsync(options)', 'camera.takePictureAsync' is undefined)] │ line: 131480, │ column: 72, └ sourceURL: 'http://localhost:8081/index.bundle?platform=android&dev=true&minify=false' }

这是我的代码：

import React, { useRef } from 'react'
import { View, Text, StyleSheet, TouchableOpacity } from 'react-native'
import { RNCamera } from 'react-native-camera'


function PlayWithCamera() {

    const camera = useRef(null)

    const takePicture = async () => {
        try {
            const options = { quality: 0.5, base64: true };
            const data = await camera.takePictureAsync(options);
            console.log(data.uri, '<<<<<<<<<<<<<<<<<<<<<');
        } catch (error) {
            console.log(error, "ERROR <<<<<<<<<<<<<")
        }
    };

    return (
        <View style={styles.container}>
            <RNCamera
                ref={camera}
                style={styles.preview}
                type={RNCamera.Constants.Type.back}
                flashMode={RNCamera.Constants.FlashMode.on}
                androidCameraPermissionOptions={{
                    title: 'Permission to use camera',
                    message: 'We need your permission to use your camera',
                    buttonPositive: 'Ok',
                    buttonNegative: 'Cancel'
                }}
                androidRecordAudioPermissionOptions={{
                    title: 'Permission to use audio recording',
                    message: 'We need your permission to use your audio',
                    buttonPositive: 'Ok',
                    buttonNegative: 'Cancel',
                }}
                onGoogleVisionBarcodesDetected={({ barcodes }) => {
                    console.log(barcodes)
                }}
            />
            <View style={{ flex: 1, width: '100%', flexDirection: 'row', justifyContent: 'center', position: 'absolute', bottom: 0 }}>
                <TouchableOpacity style={styles.capture} onPress={takePicture}>
                    <Text style={{ fontSize: 14 }}> SNAP </Text>
                </TouchableOpacity>
            </View>
        </View>
    )
}

const styles = StyleSheet.create({
    container: {
        flex: 1,
        flexDirection: 'column',
        backgroundColor: 'black',
    },
    preview: {
        flex: 1,
        justifyContent: 'flex-end',
        alignItems: 'center',
    },
    capture: {
        flex: 0,
        backgroundColor: '#fff',
        borderRadius: 5,
        padding: 15,
        paddingHorizontal: 20,
        alignSelf: 'center',
        margin: 20,
    },
})

export default PlayWithCamera

更新（18.48）：我尝试使用类组件，就像react-native-camera文档中所做的那样，它最终起作用了。但是我仍然好奇如何在函数组件中使其工作？

- Yoga Utomo

---

你能解释一下 const camera = useRef(null) 的作用吗？这会使得 camera 拥有像 takePictureAsync 这样的属性吗？也许应该这样写 const camera = useRef(RNCamera)？ - Jaromanda X

相同的错误？还是其他什么问题？ - Jaromanda X

哦，我又读了一遍错误信息... 在'camera.takePictureAsync(options)'中，'camera.takePictureAsync'未定义) 这很奇怪。 - Jaromanda X

是的，它仍然有相同的错误:/ - Yoga Utomo

const camera = useRef(new RNCamera) 是什么意思？ - Jaromanda X

Answer 1

你应该使用camera.current.takePictureAsync(options);，而不是camera.takePictureAsync(options);。

- Conor Muldoon

Answer 2

我已经让react-native-camera在函数组件中运行。以下是方法：

我使用如下步骤：

function CameraComponent(props){
  let camera;
  async function takePicture(){
    if( camera ) {
      const options = {quality: 0.5};
      const data = await camera.takePictureAsync(options);
      console.log(data.uri);
    }
  }

  return(
    <View>
      <RNCamera
        ref={ref => (camera = ref)}
       />
     </View>
  );
}

- perotta

Answer 3

我遇到了同样的问题。解决方案是回到类组件而不是函数组件。

<Camera
   ref={ref => (this.cameraEl = ref)}
   style={{ flex: 1 }}
   type={Camera.Constants.Type.front}
/>

- Eduardo Pedroso

---

虽然这样做可以起作用，但这只是一种变通方法，而不是解决方案。 - foxtrotuniform6969

Answer 4

嗨，在函数组件中正确的方式应该是：

const ref = React.createRef();

const takePicture = async () => {
    if (ref.current) {
      const options = { quality: 0.5, base64: true };
      const data = await ref.current.takePictureAsync(options);
    
      console.log(data.uri);
    }
  };


  return (
    <View style={styles.container}>
      <RNCamera
        ref={ref}
        style={styles.preview}
        type={RNCamera.Constants.Type.back}
        flashMode={RNCamera.Constants.FlashMode.on}
        androidCameraPermissionOptions={{
          title: 'Permission to use camera',
          message: 'We need your permission to use your camera',
          buttonPositive: 'Ok',
          buttonNegative: 'Cancel',
        }}
        androidRecordAudioPermissionOptions={{
          title: 'Permission to use audio recording',
          message: 'We need your permission to use your audio',
          buttonPositive: 'Ok',
          buttonNegative: 'Cancel',
        }}
        onGoogleVisionBarcodesDetected={({ barcodes }) => {
          console.log(barcodes);
        }}
      />
      <View style={{ flex: 0, flexDirection: 'row', justifyContent: 'center' }}>
        <TouchableOpacity onPress={ takePicture } style={styles.capture}>
          <Text style={{ fontSize: 14 }}> SNAP </Text>
        </TouchableOpacity>
      </View>
    </View>
  );

- andres felipe meza mendez

Answer 5

  const cameraEl = useRef(null);
  async function takePicture() {
    console.log('takePicture');
    if (cameraEl.current) {
      const options = { quality: 0.5, base64: true };
      const data = await cameraEl.current.takePictureAsync(options);
      console.log(data.uri);
    }
  }

    <RNCamera
      // ref={ref => {
      //   this.camera = ref;
      // }}
      ref={cameraEl}

- saravanakumar