I started making an a react app and added tag naming it with covid-19 tracker and on running npm start it perfectly showed the h1 heading i.e Covid 19 tracker but then I installed dependencies i.e

npm install @material-ui/core

and used some of its tags and then when I run npm start there was blank screen on my localhost:3000.

I added tags like and imported them from "@material-ui/core" so that a dropdown box will be added on running npm start but on ruuning npm start there was a blank screen ..nothing was shown..even the heading which was showing previously had gone .

I had pasted the image of App.js and localhost images below .

Code snippetlocalhosst screenshot after running dependency tags image without using dependency tags

CodePudding user response：

Material-UI/core is deprecated, it means that it is not compatible with current react version, therefore you can not use it on your project.

CodePudding user response：

As per Your first image you are calling react hook in class component or outside of functional component that is why that error is coming.

rules of hooks

And for Material-UI/core:

So Material-UI/core is now deprecated so you can't use it inside your project.

ref link

CodePudding user response：

import React from "react";

add this line at the beginning of the App.js file.