如何在 Material-UI 中的 React 中将“功能组件”转换为“类组件”

Question

Ie I want to use this Material-UI example as Class Component. How?

import React from 'react';
import Button from '@material-ui/core/Button';
import Menu from '@material-ui/core/Menu';
import MenuItem from '@material-ui/core/MenuItem';

export default function SimpleMenu() {
  const [anchorEl, setAnchorEl] = React.useState(null);

  const handleClick = event => {
    setAnchorEl(event.currentTarget);
  };

  const handleClose = () => {
    setAnchorEl(null);
  };

  return (
    <div>
      <Button aria-controls="simple-menu" aria-haspopup="true" onClick={handleClick}>
        Open Menu
      </Button>
      <Menu
        id="simple-menu"
        anchorEl={anchorEl}
        keepMounted
        open={Boolean(anchorEl)}
        onClose={handleClose}
      >
        <MenuItem onClick={handleClose}>Profile</MenuItem>
        <MenuItem onClick={handleClose}>My account</MenuItem>
        <MenuItem onClick={handleClose}>Logout</MenuItem>
      </Menu>
    </div>
  );
}

It raised many error, so I removed 'const', but still getting many issues.

Answer 1

I don't know why would you want to convert a functional component into a class based one (usually goes the other way around). But it goes something like this

import React from 'react';
import Button from '@material-ui/core/Button';
import Menu from '@material-ui/core/Menu';
import MenuItem from '@material-ui/core/MenuItem';

export default class SimpleMenu extends React.Component {
    state = {
        anchorEl: null
    }

    handleClick = event => this.setState({ anchorEl: event.currentTarget })
    handleClose = () => this.setState({ anchorEl: null })

    render() {
        const { anchorEl } = this.state
        return (
            <div>
                <Button aria-controls="simple-menu" aria-haspopup="true" onClick={this.handleClick}>
                    Open Menu
              </Button>
                <Menu
                    id="simple-menu"
                    anchorEl={anchorEl}
                    keepMounted
                    open={Boolean(anchorEl)}
                    onClose={this.handleClose}
                >
                    <MenuItem onClick={this.handleClose}>Profile</MenuItem>
                    <MenuItem onClick={this.handleClose}>My account</MenuItem>
                    <MenuItem onClick={this.handleClose}>Logout</MenuItem>
                </Menu>
            </div>
        );
    }
}

Notice that useState is a hook which isn't supported in class based components, you must use classic this.state and this.setState instead. Don't forget about this before calling your handlers: this.handleClick