不能在未挂载的组件上执行React状态更新

问题

我正在React中编写一个应用程序，无法避免一个超级常见的陷阱，即在componentWillUnmount(…)之后调用setState(…)。

我非常仔细地查看了我的代码，并试图在适当的位置放置一些保护子句，但问题仍然存在，我仍然观察到警告。

因此，我有两个问题:

我如何从堆栈跟踪中找出哪个特定的组件和事件处理程序或生命周期钩子对违反规则负责? 好吧，如何修复问题本身，因为我的代码在编写时就考虑到了这个陷阱，并且已经试图防止它，但一些底层组件仍然生成警告。

浏览器控制台

Warning: Can't perform a React state update on an unmounted component.
This is a no-op, but it indicates a memory leak in your application.
To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount
method.
    in TextLayerInternal (created by Context.Consumer)
    in TextLayer (created by PageInternal) index.js:1446
d/console[e]
index.js:1446
warningWithoutStack
react-dom.development.js:520
warnAboutUpdateOnUnmounted
react-dom.development.js:18238
scheduleWork
react-dom.development.js:19684
enqueueSetState
react-dom.development.js:12936
./node_modules/react/cjs/react.development.js/Component.prototype.setState
react.development.js:356
_callee$
TextLayer.js:97
tryCatch
runtime.js:63
invoke
runtime.js:282
defineIteratorMethods/</prototype[method]
runtime.js:116
asyncGeneratorStep
asyncToGenerator.js:3
_throw
asyncToGenerator.js:29

Code

Book.tsx

import { throttle } from 'lodash';
import * as React from 'react';
import { AutoWidthPdf } from '../shared/AutoWidthPdf';
import BookCommandPanel from '../shared/BookCommandPanel';
import BookTextPath from '../static/pdf/sde.pdf';
import './Book.css';

const DEFAULT_WIDTH = 140;

class Book extends React.Component {
  setDivSizeThrottleable: () => void;
  pdfWrapper: HTMLDivElement | null = null;
  isComponentMounted: boolean = false;
  state = {
    hidden: true,
    pdfWidth: DEFAULT_WIDTH,
  };

  constructor(props: any) {
    super(props);
    this.setDivSizeThrottleable = throttle(
      () => {
        if (this.isComponentMounted) {
          this.setState({
            pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
          });
        }
      },
      500,
    );
  }

  componentDidMount = () => {
    this.isComponentMounted = true;
    this.setDivSizeThrottleable();
    window.addEventListener("resize", this.setDivSizeThrottleable);
  };

  componentWillUnmount = () => {
    this.isComponentMounted = false;
    window.removeEventListener("resize", this.setDivSizeThrottleable);
  };

  render = () => (
    <div className="Book">
      { this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }

      <div className={this.getPdfContentContainerClassName()}>
        <BookCommandPanel
          bookTextPath={BookTextPath}
          />

        <div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
          <AutoWidthPdf
            file={BookTextPath}
            width={this.state.pdfWidth}
            onLoadSuccess={(_: any) => this.onDocumentComplete()}
            />
        </div>

        <BookCommandPanel
          bookTextPath={BookTextPath}
          />
      </div>
    </div>
  );

  getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';

  onDocumentComplete = () => {
    try {
      this.setState({ hidden: false });
      this.setDivSizeThrottleable();
    } catch (caughtError) {
      console.warn({ caughtError });
    }
  };
}

export default Book;

AutoWidthPdf.tsx

import * as React from 'react';
import { Document, Page, pdfjs } from 'react-pdf';

pdfjs.GlobalWorkerOptions.workerSrc = `//cdnjs.cloudflare.com/ajax/libs/pdf.js/${pdfjs.version}/pdf.worker.js`;

interface IProps {
  file: string;
  width: number;
  onLoadSuccess: (pdf: any) => void;
}
export class AutoWidthPdf extends React.Component<IProps> {
  render = () => (
    <Document
      file={this.props.file}
      onLoadSuccess={(_: any) => this.props.onLoadSuccess(_)}
      >
      <Page
        pageNumber={1}
        width={this.props.width}
        />
    </Document>
  );
}

更新1:取消可节流功能(仍然没有运气)

const DEFAULT_WIDTH = 140;

class Book extends React.Component {
  setDivSizeThrottleable: ((() => void) & Cancelable) | undefined;
  pdfWrapper: HTMLDivElement | null = null;
  state = {
    hidden: true,
    pdfWidth: DEFAULT_WIDTH,
  };

  componentDidMount = () => {
    this.setDivSizeThrottleable = throttle(
      () => {
        this.setState({
          pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
        });
      },
      500,
    );

    this.setDivSizeThrottleable();
    window.addEventListener("resize", this.setDivSizeThrottleable);
  };

  componentWillUnmount = () => {
    window.removeEventListener("resize", this.setDivSizeThrottleable!);
    this.setDivSizeThrottleable!.cancel();
    this.setDivSizeThrottleable = undefined;
  };

  render = () => (
    <div className="Book">
      { this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }

      <div className={this.getPdfContentContainerClassName()}>
        <BookCommandPanel
          BookTextPath={BookTextPath}
          />

        <div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
          <AutoWidthPdf
            file={BookTextPath}
            width={this.state.pdfWidth}
            onLoadSuccess={(_: any) => this.onDocumentComplete()}
            />
        </div>

        <BookCommandPanel
          BookTextPath={BookTextPath}
          />
      </div>
    </div>
  );

  getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';

  onDocumentComplete = () => {
    try {
      this.setState({ hidden: false });
      this.setDivSizeThrottleable!();
    } catch (caughtError) {
      console.warn({ caughtError });
    }
  };
}

export default Book;

当前回答

我也遇到过类似的问题，并解决了它:

通过在redux上调度一个动作，我自动地让用户登录 (将身份验证令牌置于redux状态)

然后我试图用这个来传达一个信息。设置状态({succ_message:“……”) 在我的分量中。

组件看起来是空的，控制台上出现相同的错误:“卸载组件”..“内存泄漏”等。

在我看完沃尔特在这个帖子里的回答之后

我注意到在我的应用程序的路由表中，如果用户已登录，我的组件路由无效:

{!this.props.user.token &&
        <div>
            <Route path="/register/:type" exact component={MyComp} />                                             
        </div>
}

无论令牌是否存在，我都使Route可见。

2020-05-25 13:38:54

其他回答

来自@ford04的解决方案对我来说不起作用，特别是如果你需要在多个地方使用isMounted(多个useEffect)，建议使用useRef，如下所示:

基本包

"dependencies": 
{
  "react": "17.0.1",
}
"devDependencies": { 
  "typescript": "4.1.5",
}

我的钩子组件

export const SubscriptionsView: React.FC = () => {
  const [data, setData] = useState<Subscription[]>();
  const isMounted = React.useRef(true);

  React.useEffect(() => {
    if (isMounted.current) {
      // fetch data
      // setData (fetch result)

      return () => {
        isMounted.current = false;
      };
    }
  }
});

2021-02-11 20:30:57

如果您正在从axios中获取数据，而错误仍然发生，只需将setter包装在条件中

let isRendered = useRef(false);
useEffect(() => {
    isRendered = true;
    axios
        .get("/sample/api")
        .then(res => {
            if (isRendered) {
                setState(res.data);
            }
            return null;
        })
        .catch(err => console.log(err));
    return () => {
        isRendered = false;
    };
}, []);

2020-07-24 04:24:23

我知道你没有使用历史记录，但在我的例子中，我使用了React Router DOM中的useHistory钩子，它在状态被持久化到React Context Provider之前卸载了组件。

为了解决这个问题，我使用了钩子withRouter嵌套组件，在我的情况下export default withRouter(Login)，在组件内部const Login = props =>{…;props.history.push(" /仪表盘”);…我还从组件中删除了其他props.history.push，例如，if(authorization.token)返回props.history.push('/dashboard')，因为这会导致循环，因为授权状态。

将新项目推至历史记录的替代方案。

2020-01-19 05:03:31

React已经删除了这个警告但这里有一个更好的解决方案(不仅仅是变通)

useEffect(() => {
  const abortController = new AbortController()   // creating an AbortController
  fetch(url, { signal: abortController.signal })  // passing the signal to the query
    .then(data => {
      setState(data)                              // if everything went well, set the state
    })
    .catch(error => {
      if (error.name === 'AbortError') return     // if the query has been aborted, do nothing
      throw error
    })
  
  return () => {
    abortController.abort() 
  }
}, [])

2021-10-07 17:26:09

有一个相当常见的钩子，叫做useIsMounted，可以解决这个问题(对于功能组件)…

import { useRef, useEffect } from 'react';

export function useIsMounted() {
  const isMounted = useRef(false);

  useEffect(() => {
    isMounted.current = true;
    return () => isMounted.current = false;
  }, []);

  return isMounted;
}

然后是你的功能组件

function Book() {
  const isMounted = useIsMounted();
  ...

  useEffect(() => {
    asyncOperation().then(data => {
      if (isMounted.current) { setState(data); }
    })
  });
  ...
}

2020-12-05 00:27:32

不能在未挂载的组件上执行React状态更新

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