反应本机错误：元素类型无效

Question

我在响应本机中遇到错误。该错误听起来像这样： 不变的违反：元素类型无效：预期为字符串（对于内置组件）或类/函数（对于复合组件），但得到：未定义。您可能忘记了从定义文件中导出组件，或者可能混淆了默认导入和命名导入。

这是我在主要组件（应用）中的代码：

import React from 'react';
import { StatusBar } from 'react-native';
import { createAppContainer } from 'react-navigation';
import { createMaterialBottomTabNavigator } from 'react-navigation-material-bottom-tabs';
import HomeScreen from './Home';
import CalendarScreen from './Calendar';
import SettingsScreen from './Settings';
import DarkModeContextProvider from './dark-context';
import { LanguageProvider } from './Language/Language';
import { TaskListContextProvider} from './task-context'

const AppNavigator = createMaterialBottomTabNavigator(
  {
    Home: HomeScreen,
    Calendar: CalendarScreen,
    Settings: SettingsScreen
  },
  {
    initialRouteName: 'Home',
    barStyle: { backgroundColor: '#56F2F8' }
  }
);

const AppContainer = createAppContainer(AppNavigator);

const App = () => {
  return (
    <TaskListContextProvider>
      <LanguageProvider>
        <DarkModeContextProvider>
          <AppContainer />
        </DarkModeContextProvider>
      </LanguageProvider>
    </TaskListContextProvider>
  );
};

StatusBar.setHidden(true);

export default App;