React 钩子在事件处理程序中不起作用

Question

反应版本：16.8.2

const { useState } = React;

const Dropdown = ({
  options,
  onClick,
  selected,
}) => {
  const [showDropDown, setShowDropDown] = useState(false);

  function toggleDropDown() {
    setShowDropDown(v => !v);
  }

  function createOption(o) {
    return (
      <div
        key={o}
        className='drop-down__option'
        onClick={() => {
          onClick(o);
          toggleDropDown();  
          // The following isn't working either
          // setShowDropDown(false);
        }}
       >
        {o}
      </div>
    );
  }

  return (
    <div
      onClick={toggleDropDown}
      className='drop-down'
    >
      <div>{selected}</div>
        {showDropDown && (
          <div className='drop-down__list'>
            {options.map(createOption)}
          </div>
        )}
    </div>
  );
};

const App = () => {
  const [selected, setSelected] = useState(0);

  return (
    <Dropdown
      selected={selected}
      options={[0,1,2,3]}
      onClick={v=>{setSelected(v)}}
    />
  );
}

ReactDOM.render(
  <App />,
  document.getElementById('root'),
);

所以，这是一个简单的 Dropdown，当您单击容器时，它会切换 Dropdown。

But the problem here is, after clicking one of the options, the option has been updated, but the Dropdown is not been closed.

所以在下面的代码中出现toggleDropDown();没有效果

        onClick={() => {
          onClick(o);
          toggleDropDown();  
          // The following isn't working either
          // setShowDropDown(false);
        }}

可在此处找到重现示例：https://codepen.io/vensa-albertgao/pen/ommGZe

我错过了什么？

Answer 1

将 toggleDropDown 函数更改为

function toggleDropDown() {
    setShowDropDown(!showDropDown);
}

分叉示例

https://codepen.io/anon/pen/XOOzaZ

Answer 2

你的代码中的问题是 click even on dropdown options 被传播到你再次调用 toggleDropdown onClick 的父级，因此切换发生了两次使其不明显发生。您只需要在选项上停止传播 click

const { useState } = React;

const Dropdown = ({
  options,
  onClick,
  selected,
}) => {
  const [showDropDown, setShowDropDown] = useState(false);

  function toggleDropDown() {
    console.log('called');
    setShowDropDown(v => { console.log(v); return !v});
  }

  function createOption(option) {
    return (
      <div
        key={option}
        className='drop-down__option'
        onClick={e => {
          e.stopPropagation();
          onClick(option);
          toggleDropDown();  
        }}
       >
        {option}
      </div>
    );
  }

  return (
    <div
      onClick={toggleDropDown}
      className='drop-down'
    >
      <div>{selected}</div>
        {showDropDown && (
          <div className='drop-down__list'>
            {options.map(createOption)}
          </div>
        )}
    </div>
  );
};

const App = () => {
  const [selected, setSelected] = useState(0);

  return (
    <Dropdown
      selected={selected}
      options={[0,1,2,3]}
      onClick={v=>{setSelected(v)}}
    />
  );
}

ReactDOM.render(
  <App />,
  document.getElementById('root'),
);

Working demo

React 钩子在事件处理程序中不起作用

React hook is not working from event handler

javascript

reactjs

react-hooks