在Material-UI中如何将'Functional Componenet'转换为'Class Component'

Question

即我想将此Material-UI示例用作类组件。怎么样？

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>
  );
}

它引发了许多错误，因此我删除了“ const”，但仍然遇到很多问题。

Answer 1

我不知道您为什么要将功能组件转换为基于类的组件（通常反过来）。却是这样

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>
        );
    }
}

请注意，useState是基于类的组件中不支持的钩子，必须改为使用经典的this.state和this.setState。致电处理程序之前，请不要忘记this：this.handleClick