Losing focus of an input field in a React application after typing one character

Question

I would like to seek assistance regarding an issue I'm encountering in a React application. I'm using an input field, but I've noticed that I can only input one character, and then the field loses focus.

import React, { useState } from 'react';
import { SortableContainer, SortableElement } from 'react-sortable-hoc';
import { arrayMoveImmutable } from 'array-move';


function Test() {
  const [items, setItems] = useState(['Item 1', 'Item 2', 'Item 3']);
  const [text, setText] = useState('');

  // Define a functional component for your sortable item
  const SortableItem = SortableElement(({ value }) => {
    return <li>{value}<input value={text} onChange={(e) => setText(e.target.value)}/></li>;
  });

  // Create a sortable list component
  const SortableList = SortableContainer(({ items }) => {
    return (
      <ul>
        {items.map((value, index) => (
          <SortableItem key={`item-${index}`} index={index} value={value} />
        ))}
      </ul>
    );
  });

  const addItem = () => {
    const newItem = `Item ${items.length + 1}`;
    setItems([...items, newItem]);
  };

  const onSortEnd = ({ oldIndex, newIndex }) => {
    setItems(prevItem => (arrayMoveImmutable(prevItem, oldIndex, newIndex)));
  };

  return (
    <div>
      <button onClick={addItem}>Hozzáadás</button>
      <SortableList items={items} onSortEnd={onSortEnd} />
    </div>
  );
}

export default Test;

Expected Behavior:

The expected behavior is that users should be able to freely input characters into the input field, and the focus should not be lost unexpectedly.

Problem:

The input field loses focus after typing just one character, making it impossible to input longer text.

Answer 1

The issue here is that every time a new character is typed in the input field, the entire SortableList is re-rendered. This is because the setText function is called which updates the state, triggering a re-render of the component. Since the SortableItem components are being recreated from scratch, the input field loses focus.

To solve this issue, you might want to maintain a separate state for each input field, so that only the respective input field gets updated, not the entire list. One way to do this is to store an array of strings as your state, where each string represents the text in each input field. Here's an updated version of your component that implements this approach:

function Test() {
  const [items, setItems] = useState(['Item 1', 'Item 2', 'Item 3']);
  const [texts, setTexts] = useState(['', '', '']); // Initialize an array of empty strings

  // Define a functional component for your sortable item
  const SortableItem = SortableElement(({ value, index }) => {
    return (
      <li>
        {value}
        <input
          value={texts[index]} // Use the respective string in the array
          onChange={(e) => {
            const newTexts = texts.slice(); 
            newTexts[index] = e.target.value; // Update the respective string in the array
            setTexts(newTexts);
          }}
        />
      </li>
    );
  });


}