React Context 无法使用 Provider
React Context doesn't work using Provider
我正在简化尝试使用 React 更新 context。
我希望当我单击标题时 Hello CodeSandbox
加载栏显示 context api
数据。
代码示例:
https://codesandbox.io/s/vyq3r7k4o5
正在使用上下文加载
export const LoadingState = {
loading: false
};
const LoadingContext = React.createContext(LoadingState);
export const LoadingProvider = LoadingContext.Provider;
export const LoadingConsumer = LoadingContext.Consumer;
const LinearIndeterminate = function() {
const { loading } = useContext(LoadingContext);
return (
<div>
{loading && <LinearProgress color="secondary" />}
</div>
);
};
消费者
class App extends PureComponent {
state = {
loading: false
};
add = () => {
const currentState = this.state.loading;
this.setState({ loading: !currentState });
};
render() {
console.info(this.state);
return (
<div className="App">
<h1 onClick={this.add}>Hello CodeSandbox</h1>
<Loading />
<LoadingProvider value={this.state}>
{this.state.loading}
</LoadingProvider>
<h2>Start editing to see some magic happen!</h2>
</div>
);
}
}
您的 Loading
组件应该驻留在 App 上下文提供程序中。
工作应用:https://codesandbox.io/s/z6yjl04vjx
class App extends PureComponent {
state = {
loading: false
};
add = () => {
const currentState = this.state.loading;
this.setState({ loading: !currentState });
};
render() {
console.info(this.state);
return (
<div className="App">
<h1 onClick={this.add}>Hello CodeSandbox</h1>
<LoadingProvider value={this.state}>
<Loading /> /* This line is moved. */
</LoadingProvider>
<h2>Start editing to see some magic happen!</h2>
</div>
);
}
}
我正在简化尝试使用 React 更新 context。
我希望当我单击标题时 Hello CodeSandbox
加载栏显示 context api
数据。
代码示例: https://codesandbox.io/s/vyq3r7k4o5
正在使用上下文加载
export const LoadingState = {
loading: false
};
const LoadingContext = React.createContext(LoadingState);
export const LoadingProvider = LoadingContext.Provider;
export const LoadingConsumer = LoadingContext.Consumer;
const LinearIndeterminate = function() {
const { loading } = useContext(LoadingContext);
return (
<div>
{loading && <LinearProgress color="secondary" />}
</div>
);
};
消费者
class App extends PureComponent {
state = {
loading: false
};
add = () => {
const currentState = this.state.loading;
this.setState({ loading: !currentState });
};
render() {
console.info(this.state);
return (
<div className="App">
<h1 onClick={this.add}>Hello CodeSandbox</h1>
<Loading />
<LoadingProvider value={this.state}>
{this.state.loading}
</LoadingProvider>
<h2>Start editing to see some magic happen!</h2>
</div>
);
}
}
您的 Loading
组件应该驻留在 App 上下文提供程序中。
工作应用:https://codesandbox.io/s/z6yjl04vjx
class App extends PureComponent {
state = {
loading: false
};
add = () => {
const currentState = this.state.loading;
this.setState({ loading: !currentState });
};
render() {
console.info(this.state);
return (
<div className="App">
<h1 onClick={this.add}>Hello CodeSandbox</h1>
<LoadingProvider value={this.state}>
<Loading /> /* This line is moved. */
</LoadingProvider>
<h2>Start editing to see some magic happen!</h2>
</div>
);
}
}