Reactjs 使用挂钩将数据从子组件传递到父组件

我想从子组件传递MyVariable，并在应用程序（父）组件中检索它，然后将其放在initialLang属性上

家长：

imports ...

// Here there is not "class App extends React.Component {" !!!

const App = () => (
    <Provider store={store}>
        <I18n translations={translations} initialLang="en" fallbackLang="en"></I18n>
    </Provider>
);

export default App;

imports ...

// Here there is not "class Child extends React.Component {" !!!

const ChildInner = ({context}) => (  
    {
        <View style={{flexDirection: "row"}}>   
            <Picker 
                onValueChange={(itemValue, itemIndex) => {
                    if ( itemIndex == 0 ) {
                        myVariable = 'en';
                    } else if ( itemIndex == 1 ) {
                        myVariable = 'fr';
                    }
                }} 
            >
                <Picker.Item label="English" value="en" />
                <Picker.Item label="french" value="fr" />
            </Picker>
        </View>
    }
);

const Child = (context) => (
    ...
);

Child.propTypes = {
    ....
};

Child.contextTypes = {
    t: PropTypes.func.isRequired,
};

export default Child;

导入。。。
//这里没有“类应用程序扩展React.Component{”！！！
常量应用=（）=>(
);
导出默认应用程序；

子项：

imports ...

// Here there is not "class App extends React.Component {" !!!

const App = () => (
    <Provider store={store}>
        <I18n translations={translations} initialLang="en" fallbackLang="en"></I18n>
    </Provider>
);

export default App;

imports ...

// Here there is not "class Child extends React.Component {" !!!

const ChildInner = ({context}) => (  
    {
        <View style={{flexDirection: "row"}}>   
            <Picker 
                onValueChange={(itemValue, itemIndex) => {
                    if ( itemIndex == 0 ) {
                        myVariable = 'en';
                    } else if ( itemIndex == 1 ) {
                        myVariable = 'fr';
                    }
                }} 
            >
                <Picker.Item label="English" value="en" />
                <Picker.Item label="french" value="fr" />
            </Picker>
        </View>
    }
);

const Child = (context) => (
    ...
);

Child.propTypes = {
    ....
};

Child.contextTypes = {
    t: PropTypes.func.isRequired,
};

export default Child;

导入。。。
//这里没有“类子级扩展React.Component{”！！！
const ChildInner=（{context}）=>（
{
{
如果（itemIndex==0）{
myVariable='en'；
}else if（itemIndex==1）{
myVariable='fr'；
}
}} 
>
}
);
const Child=（上下文）=>(
...
);
Child.propTypes={
....
};
Child.contextTypes={
t:PropTypes.func.isRequired，
};
导出默认子对象；

我不知道使用挂钩时如何使用道具或状态。感谢您的帮助。

在家长：

const [myVariable, setMyVariable] = useState('');
<ChildElement setMyVariable={setMyVariable}/>

---

很好的图图，但我不能使用构造函数，我没有“类Chils extensed React.Component”它与此有什么关系，理解这个概念