错误消息：

https://imgur.com/LBNyl2M

App.js

import React,{ Component } from 'react';
import { StyleSheet } from 'react-native';
import { Provider } from 'react-redux';
import Layout from './containers/Layout/Layout';

import store from './store/index';

export default function App() {

    return (

      <Provider store={store}><Layout/></Provider>

    );

}

const styles = StyleSheet.create({
  container: {
    flex: 1,backgroundColor: '#fff',alignItems: 'center',justifyContent: 'center',},});

index.js

import { createStore } from 'redux';
import reducer from './reducer';

const store = createStore(reducer);

export default store;

reducer.js

import * as actionTypes from './actions';
import moment from 'moment';

const initialState = {

    itemList: [],idCount: 0,text: 'Write your to do item!',chosenDate: 'no-date',activeItems: 0,completedItems: 0,showCompletedList: false

}

const reducer = (state = initialState,action) => {

    switch(action.type){

        case actionTypes.ADDTOLIST:

            const objItem = { 'id': state.idCount+1,'text': state.text,'date': state.chosenDate,'completed': false,'displayTextInput': false,'pickerVisible': false };
            return {
                ...state,itemList: [...state.itemList,objItem],idCount: state.idCount+1,activeItems: state.activeItems+1
            }

        case actionTypes.REMOVEFROMLIST:

            let oldItemList = [...state.itemList];
            let index = oldItemList.indexOf(action.item);

            if( index !== -1) oldItemList.splice(index,1);

            return {
                ...state,itemList: [...oldItemList],activeItems: action.item.completed ?  state.activeItems : state.activeItems-1,completedItems: action.item.completed ?  state.completedItems-1 : state.completedItems
            }

        case actionTypes.EDITITEMDATE:

            oldItemList = [...state.itemList];
            index = oldItemList.indexOf(action.item);

            if(index !== -1){
                oldItemList[index].date = state.chosenDate;
                return {
                    ...state,itemList: [...oldItemList]
                }
            }

            return state;

        case actionTypes.EDITITEMSTATUS:

            oldItemList = [...state.itemList];
            index = oldItemList.indexOf(action.item);

            if(index !== -1){
                oldItemList[index].completed = !oldItemList[index].completed;
                return {
                    ...state,activeItems: action.item.completed ?  state.activeItems+1 : state.activeItems-1,completedItems: action.item.completed ?  state.completedItems-1 : state.completedItems+1
                }
            }

            return state;

        case actionTypes.EDITITEMTEXT:

            oldItemList = [...state.itemList];
            index = oldItemList.indexOf(action.item);

            if(index !== -1){
                oldItemList[index] = state.text;
                return {
                    ...state,itemList: [...oldItemList]
                }
            }

            return state;

        case actionTypes.TOGGLETEXTINPUT:

            oldItemList = [...oldItemList];
            index = oldItemList[index].indexOf(action.item);

            if(index !== -1){
                oldItemList[index],displayTextInput = !oldItemList[index],displayTextInput;
                return {
                    ...state,itemList: [...oldItemList]
                }
            }

            return state;

        case actionTypes.FILTERactIVEITEMS:
            return {
                ...state,showCompletedList: false
            }

        case actionTypes.FILTERCOMPLETEDITEMS:
            return {
                ...state,showCompletedList: true
            }

        case actionTypes.HANDLECHANGETEXT:
            return {
                ...state,text: action.text
            }

        case actionTypes.HIDEPICKERINITEM:

            oldItemList = [...state.itemList];
            index = oldItemList[index].indexOf(item);

            if(index !== -1){
                oldItemList[index].isVisible = false;
                return {
                    ...state,itemList: [...oldItemList]
                }
            }

        case actionTypes.SHOWPICKERINITEM:

                oldItemList = [...state.itemList];
                index = oldItemList[index].indexOf(item);

                if(index !== -1){
                    oldItemList[index].isVisible = true;
                    return {
                        ...state,itemList: [...oldItemList]
                    }
                }

                return state;

        case actionTypes.HANDLEPICKER:

            return{
                ...state,chosenDate: moment(action.datetime).format('MMM,Do YYYY HH:mm') 
            }

    }

}

export default reducer;

Layout.js

import React,{ Component } from 'react';
import { Button,KeyboardAvoidingView } from 'react-native';
import AddScreen from '../../components/AddScreen/AddScreen';
import TodoList from '../../components/TodoList/TodoList';
import Header from '../../components/UI/Header/Header';

class Layout extends Component {

    state = {

        displayItems: false,pickerVisible: false

    }

    toggleItems = () => {
        this.setState({ displayItems: !this.state.displayItems });
    }

    showPicker = () => {
        this.setState({ pickerVisible: true });
    }

    hidePicker = () => {
        this.setState({ pickerVisible: false });
    }

    render () {

        let childComponent = <AddScreen 
                                toggleItems={this.props.toggleItems}
                                showPicker={this.props.showPicker}
                                hidePicker={this.props.hidePicker}
                                pickerVisible={this.props.pickerVisible}

                                />;

        if(this.props.displayItems){

            childComponent = <TodoList 
                                itemList={this.state.itemList} 
                                showCompletedList={this.state.showCompletedList}

                                />;

        }

        return (
           <KeyboardAvoidingView style={{flex:1}} behavior="padding">

                <Header />

                {childComponent}

                <Button title='Toggle Items' onPress={this.toggleItems} /> 

           </KeyboardAvoidingView>
        );
    }

}

export default Layout;

我在github上的完整项目： https://github.com/rvmelo/todolist-redux

是代码错误还是与软件包更新有关？

我收到以下错误：“ 不变违反：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。您可能忘记了从其定义的文件中导出您的组件，否则您可能混淆了默认命名导入。“