// index.js
import React from ‘react‘
import CustomTextInput from ‘./CustomTextInput‘

class Parent extends React.Component {
  constructor(props) {
    super(props);
    // 创建一个ref存储dom元素
    this.inputElement = React.createRef();
    this.getFocus = this.getFocus.bind(this)
  }

  getFocus() {
    this.inputElement.current.focus()
  }

  render() {
    return (
      <CustomTextInput
        inputRef={this.inputElement}
        inputGetFocus={this.getFocus}
      />
    )
  }
}

export default Parent

// CustomTextInput.js
import React from ‘react‘

const CustomTextInput = (props) => {
  return (
    <React.Fragment>
      <input
        type="text"
        ref={props.inputRef}
      />
      <button onClick={props.inputGetFocus}>获取焦点</button>
    </React.Fragment>
  )
}

export default CustomTextInput

// index.js
import React from ‘react‘
import CustomTextInput from ‘./CustomTextInput‘

class Parent extends React.Component {
  constructor(props) {
    super(props);
    this.getInputElement = this.getInputElement.bind(this)
    this.getFocus = this.getFocus.bind(this)
  }

  getFocus() {
    this.inputElement.focus()
  }

  getInputElement(el) {
    this.inputElement = el
  }

  render() {
    return (
      <CustomTextInput
        inputRef={this.getInputElement}
        inputGetFocus={this.getFocus}
      />
    )
  }
}

export default Parent

    <div className="ViewportDownloadForm" >
      <div
        style={{
          height: viewportElementDimensions.height,
          width: viewportElementDimensions.width,
          position: ‘absolute‘,
          left: ‘9999px‘,
        }}
        ref={ref => setViewportElement(ref)}
      >