In solution below I tried to hide uploader component based on condition.
https://stackblitz.com/edit/angular-fsda2b-svvbkj?file=app.component.html,app.component.css,app.component.ts
when I upload the file I hide
uploader component and display Remove button so we restrict uploading a new file (user must remove file before upload other file) after removing new file and display uploader component the drag and drop feature not working.