I’m trying to create react app with expo using expo-camera for taking pictures. I have separately components MeasurementCameraScreen
and MeasurementCamera
. I’m using useRef()
hook to be able to call takePictureAsync()
from the MeasuremenCameraScreen
.
When pressing the take image -button takePicture() console.logs the ref
, so I assume the onPress gets there, but then I get the following error message:
[Unhandled promise rejection: TypeError: ref.current.takePictureAsync is not a function. (In 'ref.current.takePictureAsync(options)', 'ref.current.takePictureAsync' is undefined)]
I saw that people have also had same issues with takePictureAcync(), but I haven’t found solution to my problem. I also tired to combine the MeasurementCameraScreen
and MeasurementCamera
components to one component, and with that I got the camera working, but I’m curious of why it doesn’t work now? refs
are new thing for me so I think there is something wrong with them.
Here are the components:
MeasurementCameraScreen
import { useRef } from 'react'
import { StyleSheet, TouchableOpacity, View } from 'react-native'
import MeasurementCamera from '../components/MeasurementCamera'
import Text from '../components/Text'
const MeasurementCameraScreen = () => {
const cameraRef = useRef(null)
return (
<View style={styles.container}>
<View style={styles.cameraContainer}>
<MeasurementCamera ref={cameraRef}/>
</View>
<View>
</View>
<TouchableOpacity
onPress={() => cameraRef.current.takePicture()}
style={styles.buttonContainer}
>
<Text>
Take image
</Text>
</TouchableOpacity>
</View>
)
}
const styles = StyleSheet.create({
container: {
flex: 1,
},
cameraContainer: {
flex: 1,
},
buttonContainer: {
width: '100%',
height: 70,
backgroundColor: 'white',
justifyContent: 'center',
alignItems: 'center',
alignSelf: 'flex-end'
},
})
export default MeasurementCameraScreen
MeasurementCamera
import { useState, useEffect, useImperativeHandle, forwardRef } from 'react'
import { StyleSheet } from "react-native"
import { Camera } from 'expo-camera'
import Text from './Text'
const MeasurementCamera = forwardRef((props, ref) => {
const [hasPermission, setHasPermission] = useState(null)
useEffect(() => {
const getPermission = async () => {
const { status } = await Camera.requestCameraPermissionsAsync()
setHasPermission(status === 'granted')
}
getPermission()
}, [])
const takePicture = async () => {
if (ref) {
console.log(ref.current)
const options = {
quality: 1,
base64: true
}
const picture = await ref.current.takePictureAsync(options)
console.log(picture.uri)
}
}
useImperativeHandle(ref, () => ({
takePicture
}))
if (hasPermission === null) {
return <Text>Requesting for camera permission</Text>
} if (hasPermission === false) {
return <Text>No access to camera</Text>
}
return (
<Camera
ref={ref}
style={StyleSheet.absoluteFillObject}
/>
)
})
MeasurementCamera.displayName = 'MeasurementCamera'
export default MeasurementCamera
2
Answers
Okay I found the solution!
After reading the medium article @LouaySleman recommended about the expo-camera I understood that to be able to use the
Expo Camera
components functions I need to useref
. So what I needed was two refs, one for the components to communicate and another one to be able to use theCamera
takePictureAsync()
function.What you needed is to add two refs, one for the components to
communicate
and another one to be able to use the CameratakePictureAsync()
function Please check this example from medium: