Image onError Handling in React

问题

I am trying to grab the maxresdefault of multiple YouTube thumbnails. Some YouTube videos simply don't have a high res thumbnail photo so I want to catch that with an onError prop on an img element. For some reason my function is not triggering when I get the 404 img error. Any ideas? Thanks in advance.

class FeaturedVideo extends Component<Props> {
  addDefaultSrc = (e) => {
    e.target.src = this.props.background.replace("maxresdefault", "hqdefault")
  }

  renderVideo = (props) => (
    <div
      style={{
        width: "100%",
        height: "100%",
        backgroundSize: "contain",
      }}
      className="featured-community-video"
    >
      <img onError={this.addDefaultSrc} src={props.background} alt="" />
      <div className="featured-community-video-title">
        <h2 style={{ fontSize: "0.8em" }}>WATCH</h2>
        <h1 style={{ fontSize: props.titleFontSize }}>{props.title}</h1>
      </div>
    </div>
  )

  render() {
    return (
      <div
        key={this.props.postId}
        style={{
          width: this.props.width,
          height: "50%",
        }}
        className="featured-community-video-container"
      >
        <Link to={routeCodes.POST_DETAILS(this.props.postId)}>
          {this.renderVideo(this.props)}
        </Link>
      </div>
    )
  }
}

回答1:

To achieve this, I would suggest rendering the <img /> based on the state of your <FeatureVideo/> component.

You could for instance, create an Image object, attempt to load the background image and by this, reliably determine if the image fails to load. On the images success or failure to load, you would then setState() on your <FeaturedVideo/> component with the appropriate background value which would instead be used to rendering you actual <img/> element:

class FeaturedVideo extends Component<Props> {

  componentDidMount() {

    if(this.props.background) {

      // When component mounts, create an image object and attempt to load background
      fetch(this.props.background).then(response => {
         if(response.ok) {
           // On success, set the background state from background
           // prop
           this.setState({ background : this.props.background })
         } else {        
           // On failure to load, set the "default" background state
           this.setState({ background : this.props.background.replace("maxresdefault", "hqdefault") })
         }
      });
    }
  }

  // Update the function signature to be class method to make state access eaiser
  renderVideo(props) {

    return <div
      style={{
        width: "100%",
        height: "100%",
        backgroundSize: "contain",
      }}
      className="featured-community-video">

      {/* Update image src to come from state */}

      <img src={this.state.background} alt="" />
      <div className="featured-community-video-title">
        <h2 style={{ fontSize: "0.8em" }}>WATCH</h2>
        <h1 style={{ fontSize: props.titleFontSize }}>{props.title}</h1>
      </div>
    </div>
  }

  render() {
    return (
      <div
        key={this.props.postId}
        style={{
          width: this.props.width,
          height: "50%",
        }}
        className="featured-community-video-container"
      >
        <Link to={routeCodes.POST_DETAILS(this.props.postId)}>
          {this.renderVideo(this.props)}
        </Link>
      </div>
    )
  }
}

Hope that helps!

来源：https://stackoverflow.com/questions/52999458/image-onerror-handling-in-react

标签

javascript

reactjs

image

youtube

onerror