更新状态后，react 组件不会重新渲染

Question

I have this react functional component where I have file input . after I choose the file I assume the text in h1 tag should convert from choose file to test but nothing happen

• the handleChange function gets fired
• the console.log print state.show : true
• the INSIDE console.log() print state.show : true but does not show the string test

import React, { useState } from 'react';

export default ({ selectedFile }) => {
  const [state, setState] = useState({});

  const handleChange = e => {
    console.log('in handleChange');
    setState({ ...state, show: true });
  };
  console.log('My state: ', state);
  return (
    <div className='file-uploader'>
      <input type='file' id='upload' hidden onChange={handleChange} />
      <label htmlFor='upload'>
        {state.show ? <h1> {console.log('INSIDE ', state)} test</h1> : <h1>choose file</h1>}
      </label>
    </div>
  );
};

Answer 1

You need the following property {show: false} in your initial state.

import React, { useState } from 'react';

export default ({ selectedFile }) => {
  const [state, setState] = useState({show: false});

  const handleChange = e => {
    console.log('in handleChange');
    setState({ ...state, show: true });
  };
  console.log('My state: ', state);
  return (
    <div className='file-uploader'>
      <input type='file' id='upload' hidden onChange={handleChange} />
      <label htmlFor='upload'>
        {state.show ? <h1>test</h1> : <h1>choose file</h1>}
      </label>
    </div>
  );
};

Live Demo