输入时反应输入失去焦点

Question

我不明白为什么在另一个组件中定义组件时输入一个字符后输入会失去焦点。我阅读了其他答案以使用 ref。但它不起作用。

不起作用：

import React, { useState, useRef } from "react";
import ReactDOM from "react-dom";


function MyApp() {
  const [text1, setText1] = useState("");
  const [text2, setText2] = useState("");
  const ref1 = useRef(null)
  const ref2 = useRef(null)

  const TextInput = ({ref, text, onChange }) => {
    return <input ref={ref} defaultValue={text} onChange={onChange} />;
  };
  

  const onChange1 = e => {
    setText1(e.currentTarget.value);
  };

  const onChange2 = e => {
    setText2(e.currentTarget.value);
  };
  return (
    <form className="App">
      <TextInput ref={ref1} text={text1} onChange={onChange1} />
      <TextInput ref={ref2} text={text2} onChange={onChange2} />
    </form>
  );
}

const rootElement = document.getElementById("root");
ReactDOM.render(<MyApp />, rootElement);

当我在外部定义组件时，一切正常。

有效：

import React, { useState, useRef } from "react";
import ReactDOM from "react-dom";


const TextInput = ({ref, text, onChange }) => {
  return <input ref={ref} defaultValue={text} onChange={onChange} />;
};


function MyApp() {
  const [text1, setText1] = useState("");
  const [text2, setText2] = useState("");
  const ref1 = useRef(null)
  const ref2 = useRef(null)



  const onChange1 = e => {
    setText1(e.currentTarget.value);
  };

  const onChange2 = e => {
    setText2(e.currentTarget.value);
  };
  return (
    <form className="App">
      <TextInput ref={ref1} text={text1} onChange={onChange1} />
      <TextInput ref={ref2} text={text2} onChange={onChange2} />
    </form>
  );
}

const rootElement = document.getElementById("root");
ReactDOM.render(<MyApp />, rootElement);

JS Fiddle

Answer 1

每当输入值更改并且MyApp 组件呈现时，您都在重新创建TextInput。如果你想在MyApp 组件中包含TextInput 组件，你可以使用useCallback 钩子来防止在组件渲染时重新创建TextInput。

JSFiddle

import React, { useState, useRef, useCallback } from "react";
import ReactDOM from "react-dom";

function MyApp() {
      const [text1, setText1] = useState("");
      const [text2, setText2] = useState("");
      const ref1 = useRef(null);
      const ref2 = useRef(null);

      const TextInput = useCallback(({ ref, text, onChange }) => {
        return <input ref={ref} defaultValue={text} onChange={onChange} />;
      }, []);

      const onChange1 = e => {
        setText1(e.currentTarget.value);
      };

      const onChange2 = e => {
        setText2(e.currentTarget.value);
      };
      return (
        <form className="App">
          <TextInput ref={ref1} text={text1} onChange={onChange1} />
          <TextInput ref={ref2} text={text2} onChange={onChange2} />
        </form>
      );
}

const rootElement = document.getElementById("root");
ReactDOM.render(<MyApp />, rootElement);