如何使用反应参考设置背景图像？

Question

I would like to set a background to a certain div using react ref, here is what I have tried so far:

The class component:

import React from 'react';
import PropTypes from 'prop-types';
import classnames from 'classnames';

export default class CalendarDay extends React.Component {
    constructor(props) {
        super(props);

        this.backgroundImageRef = React.createRef();
    }
    render () {

        let { day, isToday, events, onClick } = this.props;
        const dayClasses = classnames({
            'flexColumn': true,
            'day': true,
            'inactive': day.siblingMonth,
            'today': isToday,
        });

        if(typeof day.eventSlots !== 'undefined' && day.eventSlots.length > 0 ) {

          let getEventData = Object.values(day.eventSlots)[0].eventClasses;

          switch (getEventData) {
              case 'event1':
                  let getInnerGrid = this.backgroundImageRef.current;
                  console.log(getInnerGrid); // returns null
                  //event1.style.backgroundImage = "url('../images/eventbg1.svg')";
                  console.log(getEventData);
                  break;

              default:
                  break;
          }
        } 

        return (
            <div 
                onClick={onClick.bind(null, this, day)}
                className={dayClasses}>
                <div ref={this.backgroundImageRef} className="inner-grid">
                    <div className="date">
                        {day.day}
                    </div>

                    {events}
                </div>
            </div>
        );
    }
}

CalendarDay.propTypes = {
    day: PropTypes.object.isRequired,
    isToday: PropTypes.bool,
    events: PropTypes.array,
    onClick: PropTypes.func,
};

Now when I run the app and check the console, I see the null. What am I doing wrong here?

Answer 1

You can create a bgStyle , and update bgStyle based on condition . Then u can directly use on div as style prop.

let bgStyle = {}
if(typeof day.eventSlots !== 'undefined' && day.eventSlots.length > 0 ) {

  let getEventData = Object.values(day.eventSlots)[0].eventClasses;

  switch (getEventData) {
    case 'event1':
      bgStyle.backgroundImage = "url('../images/eventbg1.svg')"
      break;
    default:
      break;
  }
} 

return (
  <div style={bgStyle} className="inner-grid">
    <div className="date">
      {day.day}
    </div>
    {events}
  </div>
);