尝试在 typescript 中使用 React useref 时出错

Question

使用 React 和 typescript 我正在构建一个选项卡组件，您可以在其中从顶部从左到右滚动选项卡链接并溢出：滚动集。 这适用于触控板，但我需要为鼠标用户实现一种方法，以便他们可以像在此 codepen 中一样单击和滚动： https://codepen.io/thenutz/full/VwYeYEE到目前为止我为选项卡链接的代码它位于选项卡内容上方，如下所示：

<div className='container'>
  <div className='flex-row'
    sx={{ overflow: 'scroll',
    '::-webkit-scrollbar': { display: 'none' },
    display: flex,
    flexDirection: 'row',
    flexWrap: 'no-wrap' }}>
    <div className='tabLinks'
       sx={{display: 'flex', flexDirection: 'row', flexWrap: 'no-wrap'}}>
      {React.Children.map(children, (child, index) => ( //LOOPS THROUGH TAB LINKS HERE ))}
    </div>
  </div>
</div>

tabLinks div 是需要通过触控板和鼠标水平滚动的 div（单击并拖动）

我第一次尝试这样做是使用 react useRef 为具有 ClassName 'tabLinks' 的 div 创建一个 ref

const ref = React.useRef<HTMLDivElement>(null)

然后将此 ref 传递给 tabLinks div，我尝试按照 codepen 示例实现 onMouseDown 事件，但在下面遇到此错误：

Property 'offsetLeft' does not exist on type 'RefObject<HTMLDivElement>'

任何帮助将非常感激。

编辑：

这是我到目前为止所尝试的：

const ref = React.useRef<HTMLDivElement>(null)
  let startX
  let scrollLeft

<div className='container'>
  <div className='flex-row'
    sx={{ overflow: 'scroll',
    '::-webkit-scrollbar': { display: 'none' },
    display: flex,
    flexDirection: 'row',
    flexWrap: 'no-wrap' }}>
        <div
          className='items'
          sx={{
            display: 'flex', 
            flexDirection: 'row',
            flexWrap: 'no-wrap'
           }}
          ref={ref}
          onMouseDown={e => {
            isDown= true
            const offset = ref.current?.offsetLeft || 0
            startX = e.pageX - offset
            scrollLeft = ref.current?.scrollLeft
          }}
          onMouseUp={e => {
            isDown = false;
          }}
          onMouseLeave={e => {
            isDown = false
          }}
          onMouseMove={e => {
            if(!isDown) return;
            e.preventDefault();
            const x = e.pageX - (ref.current?.offsetLeft ?? 0)
            const walk = (x - startX) * 3; //scroll-fast
            ref.scrollLeft = scrollLeft - walk
            console.log(walk)
          }}
        >
      {React.Children.map(children, (child, index) => ( //LOOPS THROUGH TAB LINKS HERE ))}
    </div>
  </div>
</div>

我现在收到此错误

Uncaught TypeError: Cannot add property scrollLeft, object is not extensible
    at onMouseMove (index.tsx:102)
    at HTMLUnknownElement.callCallback (react-dom.development.js:149)
    at Object.invokeGuardedCallbackDev (react-dom.development.js:199)
    at invokeGuardedCallback (react-dom.development.js:256)
    at invokeGuardedCallbackAndCatchFirstError (react-dom.development.js:270)
    at executeDispatch (react-dom.development.js:561)
    at executeDispatchesInOrder (react-dom.development.js:583)
    at executeDispatchesAndRelease (react-dom.development.js:680)
    at executeDispatchesAndReleaseTopLevel (react-dom.development.js:688)
    at forEachAccumulated (react-dom.development.js:662)

Answer 1

const offset = ref.current?.offsetLeft?? 0;

同样适用于：

scrollLeft = ref.current?.scrollLeft?? 0;

这确保了当当前 ref 为 null 时两个变量都有一个数值。

您将需要 null 合并运算符。 如果您没有可用的，请使用：

const offset = ref.current?.offsetLeft || 0; scrollLeft = ref.current?.scrollLeft || 0;