React-navigation 3中的createBottomTabNavigator，不起作用

Question

   const MainFooterNavigator = createBottomTabNavigator(
{
        Feeds: {
            screen: FeedsScreen
        },
        Camera: {
            screen: CameraScreen
        },
        Profile: {
            screen: ProfileScreen
        }
    },
)



const AppNavigator = createSwitchNavigator(
    {

        AuthFlow: {
            screen: AuthNavigator 
        },
        MainFlow: {
            screen: MainFooterNavigator
        } 
    },
    {
        initialRouteName: 'AuthFlow'
    }   
)


module.exports = {
        AppContainer: createAppContainer(AppNavigator)
}

此AppContainer在App.js中用作

 <View>
      <AppContainer/>
 </View>

加载MainFlow时未获取“底部”标签导航器。请帮帮我， 我做错了什么吗？ 使用react-navigation 3（最新）