在 React 中传递 refs

Question

In my App component, I have 2 components Navbar and View . In my Navbar component, I have an ExportButton component which onClick should generate a screenshot of the View component by passing its ref.

App.js

function App() {
  const view = useRef();
  return (
    <div className="App">
      <Navbar takeSnap={view}/>
      <View ref={view}/>
    </div>
  );
}

Navbar.js

const Navbar = ({ takeSnap }) => {
  return (
    <>
      <Lists />
      <ExportButton takeSnap={takeSnap} />
    </>
  );
};

Button.js

const ExportButton = ({ takeSnap }) => {
 function handleClick(takeSnap) {
    domtoimage.toBlob(takeSnap.current, {}).then(function (blob) {
      saveAs(blob, "myImage.png");
    });
  }
   return (
      <Button onClick={() => handleClick(takeSnap)} />
   );
};

I having some trouble passing ref of View to use the library dom-to-image to take a screenshot. The error says "Uncaught (in promise) TypeError: Cannot read property 'cloneNode' of undefined at makeNodeCopy". This might be a quick fix but I'm not sure where I'm going wrong.

Answer 1

You cannot create a ref for a component, a ref can only reference a DOM element. When you do:

<View ref={view}/>

ref is a reserved keyword and it won't be passed down to your View render function.

You can use forwardRef to solve this problem, or simply use a different keyword such as myRef:

<View myRef={view}/>

Then when you render your View , you can assign this ref to the element you want the screenshot from:

<div ref={myRef} ...