React input loses focus on onChange-CodePudding

I'm making a React application and I need a table where each row contains an input. For that, I'm using Material-UI and Formik, but I have a bug that anytime I type something in one of the inputs, I lose the focus of that input. I saw this bug a lot on the internet, I tried with adding keys, deleting keys, use defaultValue instead of value, and anything worked properly for me.

I've created a codesandbox for this: https://codesandbox.io/s/gracious-robinson-i69v3?file=/src/App.js

If anyone could help me I would really appreciate, I'm stuck with this problems for a few days.

CodePudding user response：

Everytime your MyInput components rerenders, it key changes because it's non deterministic (it uses Math.random()). Because of this, React will remove the existing DOM node and insert a new DOM node in it's place. Your browser now thinks it's an other element, so it does not put focus on that element.

CodePudding user response：

You don't have to set the key property on every component. It's just needed where you output an array of elements, e.g. when using map. So in your example only the Formik component needs to have the key property set, because it's the parent of the other components inside the loop.

     {companies.map((company, index) => (
          <Formik
            key={index}
            initialValues={{
              contact_name: company.contact_name || "",
              contact_email: company.contact_email || ""
            }}
            onSubmit={(values) => {
              console.log(values);
            }}
          >
            {(formik) => (
...