我正在尝试通过“ react-native-camera”将相机用于rect本地应用。 当我尝试导航到相机屏幕时，我一直收到以下错误。

这是我的代码：

import React,{Component} from 'react';
import {SafeAreaView,StyleSheet,TouchableOpacity,TextInput,View,Text,StatusBar,Image} from 'react-native';
import {createAppContainer} from 'react-navigation';
import {createStackNavigator} from 'react-navigation-stack';
import UserMainScreen from './UserMainScreen.js';
import Camera from 'react-native-camera';
import {RNCamera} from 'react-native-camera';

class CameraScreen extends Component{
    render(){
        return(
            <View style={cam_styles.container}>
                <Camera ref={cam=>{this.camera = cam;}} style={cam_styles.preview} aspect = {Camera.constants.Aspect.fill}>
                        <Text style={cam_styles.capture} onPress={this.takePicture.bind(this)}>[CAPTURE]</Text>
                    </Camera>
            </View>
        );
    }

    takePicture(){
        const options ={};
        this.camera.capture({metadata: options})
        .then(data=>console.log(data))
        .catch(error=>console.log(error));
    }
}

const cam_styles = StyleSheet.create({
    container: {
        flex:1,flexDirection: 'row',},preview:{
        flex:1,justifyContent: 'flex-end',alignItems:'center'
    },capture:{
        flex:0,backgroundColor: '#fff',borderRadius: 5,color:'#000',padding:10,margin:40
    }
});

const MainNavigator = createStackNavigator({
    Home: UserMainScreen,Login : LoginScreen,Camera : CameraScreen,{
        initialRouteName: 'Login',headerMode: 'none',}
);
const AppContainer = createAppContainer(MainNavigator);

class Login extends Component{

    render (){      
        return (
                <AppContainer />   
        );
    }
}
export default Login;

这是我不断遇到的错误。我尝试删除了Aspect属性，但得到了Invariant Violation: Element type is invalid: expected a string (for built-in components) or class/function but got undefined. Check the render method of CameraScreen

使用我当前的代码，这是我得到的错误日志。我该如何解决？

TypeError: undefined is not an object (evaluating '_reactNativeCamera.Camera.constants')

This error is located at:
    in CameraScreen (at SceneView.js:9)
    in SceneView (at StackViewLayout.tsx:900)
    in RCTView (at createAnimatedComponent.js:151)
    in AnimatedComponent (at StackViewCard.tsx:106)
    in RCTView (at createAnimatedComponent.js:151)
    in AnimatedComponent (at screens.native.js:71)
    in Screen (at StackViewCard.tsx:93)
    in Card (at createPointerEventsContainer.tsx:95)
    in Container (at StackViewLayout.tsx:975)
    in RCTView (at screens.native.js:101)
    in ScreenContainer (at StackViewLayout.tsx:384)
    in RCTView (at createAnimatedComponent.js:151)
    in AnimatedComponent (at StackViewLayout.tsx:374)
    in PanGestureHandler (at StackViewLayout.tsx:367)
    in StackViewLayout (at withOrientation.js:30)
    in withOrientation (at StackView.tsx:104)
    in RCTView (at Transitioner.tsx:267)
    in Transitioner (at StackView.tsx:41)
    in StackView (at createNavigator.js:80)
    in Navigator (at createKeyboardAwareNavigator.js:12)
    in KeyboardAwareNavigator (at createAppContainer.js:430)
    in NavigationContainer (at Login.js:97)
    in Login
    in RCTView (at AppContainer.js:101)
    in RCTView (at AppContainer.js:119)
    in AppContainer (at renderApplication.js:39)

CameraScreen#render
    Login.js:42:100
renderRoot
    [native code]:0
runRootCallback
    [native code]:0
unstable_runWithPriority
    scheduler.development.js:643:23
callFunctionReturnFlushedQueue
    [native code]:0