Hi Allan, I'd like to help you with your question.
There can be many reasons someone might act in this way and demand your complete attention. But the main reason may be that the person is narcissistic. When someone is narcissistic. they have an extreme preoccupation with themselves. They show little concern with others, unless the other person's focus is on them. People who are narcissistic have the view that they are more important than others and they are interested in their own needs only. Your friend may feel that they need this level of attention from you because they feel what they say is of the utmost importance where what you say is not important at all.
Another possibility is that your friend was abused somehow as a child and they learned that they need to force people to listen to them so they feel validated. Maybe they were never listened to or the only time they felt they were valued is when they had something dramatic to say.
The fact that your friend refuses to listen to anything you have to say makes your relationship unbalanced. You may want to try telling your friend you feel he/she is not listening to you and you feel left out. Or you can re think the relationship in favor of a more balanced one where you are treated as being on equal footing.
I hope this helps you,Kate