CODEWITHSUNDEEP
reactjs
Bo Yang
Bo Yang

Reputation: 33

how to get the dom's true height by reactjs?

There is a reactjs component, i need to get the heigth of a dom in component. But i failed, i don't know which is wrong. This is my code:

class ImgCropper extends React.Component {

  constructor(props) {
    super(props);
    this.state = {
      containSize: { width: 0, height: 0 },
    };
  }

  componentDidMount() {
    console.log('=================组件的宽高：', this.image.offsetWidth, this.image.offsetHeight);
    this.middle.style.width = `${this.contain.offsetWidth}px`;
    this.middle.style.height = `${this.contain.offsetWidth}px`;
    // 配置图片的宽高
    this.image.style.transform = `translate(0px,${parseInt((this.contain.offsetHeight - this.image.height) / 2, 10)}px)`;
  }

  render() {
    return (<div ref={((div) => { this.contain = div; })} className={styles.container}>
      <div id="cover-top" ref={(div) => { this.top = div; }} className={styles.coverTop}>
        <a href="">
          <input id="imageFile" name="image" type="file" accept="image/gif, image/jpeg, image/jpeg" />点击上传
        </a>
        <button >选择图片</button>
        <input id="x" name="x" />
        <input id="y" name="y" />
        <input id="width" name="width" />
        <input id="height" name="height" />
      </div>
      <div id="cover-middle" ref={(div) => { this.middle = div; }} className={styles.coverMiddle} />
      <div id="cover-down" ref={(div) => { this.down = div; }} className={styles.coverDown}>
        <button type="button" >获得裁剪参数</button><span id="params">12121</span>
      </div>
      <img id="image" ref={(image) => { this.image = image; }} className={styles.image} draggable="true" src={test} />
    </div>
    );
  }

The console log show the dom's height is 0 always.

Upvotes: 0

Views: 54

Answers (1)

blaz
blaz

Reputation: 4078

You forgot to consider loading image time. At the time componentDidMount is triggered, the React component was rendered, but the <img> element just starts loading image from given URL. Here you need to bind onLoad event of <img> with a function, and retrieve image size inside that function.

Sample code:

class ImgCropper extends React.Component {

  constructor(props) {
    super(props);
    this.state = {
      containSize: { width: 0, height: 0 },
    };
    this.onImageLoad = this.onImageLoad.bind(this);
  }

  onImageLoad() {
    console.log('=================组件的宽高：', this.image.offsetWidth, this.image.offsetHeight);
    this.middle.style.width = `${this.contain.offsetWidth}px`;
    this.middle.style.height = `${this.contain.offsetWidth}px`;
    // 配置图片的宽高
    this.image.style.transform = `translate(0px,${parseInt((this.contain.offsetHeight - this.image.height) / 2, 10)}px)`;
  }

  render() {
    return (<div ref={((div) => { this.contain = div; })} className={styles.container}>
      <div id="cover-top" ref={(div) => { this.top = div; }} className={styles.coverTop}>
        <a href="">
          <input id="imageFile" name="image" type="file" accept="image/gif, image/jpeg, image/jpeg" />点击上传
        </a>
        <button >选择图片</button>
        <input id="x" name="x" />
        <input id="y" name="y" />
        <input id="width" name="width" />
        <input id="height" name="height" />
      </div>
      <div id="cover-middle" ref={(div) => { this.middle = div; }} className={styles.coverMiddle} />
      <div id="cover-down" ref={(div) => { this.down = div; }} className={styles.coverDown}>
        <button type="button" >获得裁剪参数</button><span id="params">12121</span>
      </div>
      <img id="image" ref={(image) => { this.image = image; }} className={styles.image} draggable="true" src={test} onLoad={this.onImageLoad} />
    </div>
    );
  }
}

Upvotes: 1

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