CustomWebView(Saving Login details)

Good morning sir. I link a website that have logins details to my app. How can I save a login details ( username and password) permanently using CustomWebView. So that users won't be typing the login details anytime the use the app.

Store name and username in a TinyDB.

Thank you for your reply.
I link a webpage to my app. I am not the one giving the login details but each user of the website have different login details. I want a situation whereby if the login using the app it will ask do want to save your username and password.

Thank you sir, I will try this