我正在尝试使用 ReactJS 创建图形编辑器。我有 Workspace 组件。此组件使用画布绘制对象。 Workspace 组件是 React 类组件。 我无法获取 render() 方法中的 HTML 元素。

我无法使用 document.getElementById(..) ，我决定使用 React Refs 。这更像是干净的。

我遇到了这样的错误：

TypeError: Cannot read property 'getContext' of null

import React, { Component } from 'react';
import './Workspace.css';

// Workspace component is resposiable for drawing defferent elements on the screen
// It uses canvas API to draw elements and the stuff like that
export default class Workspace extends Component {

    constructor(props) {

        // Calling parent`s constructor function
        super(props);

        // All objects that will be drawn
        this.objects = [];

        // Creating the `canvasRef` ref for having access to the canvas element
        this.canvasRef = React.createRef();

        // Getting the canvas element, using the`canvasRef` ref
        const canvas = this.canvasRef.current;

        // Creating context
        this.context = canvas.getContext('2d');

    }

    render() {
        return (
            <div className="workspace">
                <canvas className="canvas" ref={this.canvasRef}></canvas>
            </div>
        )
    }
}