React Context和Next JS

我正在尝试向我的应用程序添加简单的React Context。我在“ ./components/DataProvider.js”中创建上下文，如下所示：

import React, { Component } from 'react'

const DataContext = React.createContext()

class DataProvider extends Component {
    state = {
        isAddButtonClicked: false
    }

    changeAddButtonState = () => {
        if( this.state.isAddButtonClicked ) {
            this.setState({
                isAddButtonClicked: false
            })
        } else {
            this.setState({
                isAddButtonClicked: true
            })            
        }
    }

    render() {
        return(
            <DataContext.Provider
                value={{
                    isAddButtonClicked: this.state.isAddButtonClicked,
                    changeAddButtonState: () => {
                        if( this.state.isAddButtonClicked ) {
                            this.setState({
                                isAddButtonClicked: false
                            })
                        } else {
                            this.setState({
                                isAddButtonClicked: true
                            })            
                        }
                    }
                }}
            >
                {this.props.children}
            </DataContext.Provider>
        )
    }

}

const DataConsumer = DataContext.Consumer

export default DataProvider
export { DataConsumer }

然后我添加到“ ./pages/_app.js”中

import App, { Container } from 'next/app'

import DataProvider from '../components/DataProvider'

class MyApp extends App {
render () {
    const { Component, pageProps } = this.props
    return (
    <Container>
        <DataProvider>
        <Component {...pageProps} />
        </DataProvider>
    </Container>
    )
}
}

export default MyApp

并在“ ./components/AddPostButton.js”中使用它。

import React, {Component} from 'react'
import { DataConsumer } from './DataProvider'

import { FontAwesomeIcon } from '@fortawesome/react-fontawesome'
import { faPlus } from '@fortawesome/free-solid-svg-icons'

class AddPostButton extends Component {
    render() {
        return (
            <div>
                <DataConsumer>
                    {({ changeAddButtonState }) => (
                        <a onClick={changeAddButtonState}>
                            <FontAwesomeIcon icon={faPlus} color='#fff' />
                        </a>
                    )}
                </DataConsumer>
            </div>

        )
    }

}

export default AddPostButton

但我收到此错误“无法读取未定义的属性'changeAddButtonState'”。我正在使用React 16.7和NextJS 7.0.2。不知道怎么了。

第二个问题是我应该对所有内容使用一个上下文还是将其用作MVC模式中的模型？