React Beginner Question: Textfield Losing Focus On Update

I see two main issues:

1. How you are defining your different components (nesting component types)
2. Not passing the index prop through to components that are expecting it

You have the following structure (leaving out details that are not directly related to my point):

export default function Form(props) {

  const onMediaDeliverableChange = index => (deliverableData, e) => {
    props.setMediaDeliverable(deliverableData, index);
  }

  const MediaDeliverableCheckBoxList = ({values, label}) => (
    <FormGroup>
    {values.map((value, index) => (
        <MediaDeliverablesCheckBox key={index} onMediaDeliverableChange={onMediaDeliverableChange(index)}/>
      ))}
    </FormGroup>
    );

  return (
      <MediaDeliverableCheckBoxList/>
  );
}

The function MediaDeliverableCheckBoxList represents the component type used to render the <MediaDeliverableCheckBoxList/> element. Whenever Form is re-rendered due to props or state changing, React will re-render its children. If the component type of a particular child is the same (plus some other criteria such as key being the same if specified), then it will update the existing DOM node(s). If the component type of a particular child is different, then the corresponding DOM nodes will be removed and new ones added to the DOM.

By defining the MediaDeliverableCheckBoxList component type within the Form function, you are causing that component type to be different on every render. This will cause all of the DOM nodes to be replaced rather than just updated and this will cause the focus to go away when the DOM node that previously had focus gets removed. It will also cause performance to be considerably worse.

You can fix this by moving this component type outside of the Form function and then adding any additional props that are needed (e.g. onMediaDeliverableChange) to convey the context known inside of Form. You also need to pass index as a prop to MediaDeliverablesCheckBox since it is using it.

const MediaDeliverableCheckBoxList = ({values, label, onMediaDeliverableChange}) => (
    <FormGroup>
    {values.map((value, index) => (
        <MediaDeliverablesCheckBox key={index} index={index} onMediaDeliverableChange={onMediaDeliverableChange(index)}/>
      ))}
    </FormGroup>
);


export default function Form(props) {

  const onMediaDeliverableChange = index => (deliverableData, e) => {
    props.setMediaDeliverable(deliverableData, index);
  }


  return (
      <MediaDeliverableCheckBoxList onMediaDeliverableChange={onMediaDeliverableChange}/>
  );
}

You have this same issue with CheckboxGroup and possibly other components as well.

This issue is solely because of your key in the TextField. You must ensure that the key remains the same on every update. Otherwise you would the face the current issue.