Word for someone who changes hobbies constantly

Question

I have a friend who seems to adopt new hobbies on a weekly basis. As in, "I would really like to get in to knife throwing, let me buy a knife for that," and then abandons the idea a week later. There is no particular theme to these hobbies: it can be anything from card counting to hatchet throwing. Words like "indecisive" don't seem to fit exactly, because he is very decisive once he sets his mind on something. He is not incapable of making a decision; he is incapable of sticking to a decision.

Is there a word to describe someone like this?

Answer 1

Fickle describes someone who frequently changes their mind. It can be applied to one's interests.

From Lexico:

Changing frequently, especially as regards one's loyalties or affections.

Answer 2

You might be looking for "inconsistent".

As mentioned in the dictionary, the meaning of "inconsistent" is:

3. not consistent in principles, conduct, etc.:
   He's so inconsistent we never know if he'll be kind or cruel.

And the meaning of "consistent" is:

2. constantly adhering to the same principles, course, form, etc.:
   a consistent opponent.