grammar - What is the difference between "〜がる" and "〜がっている"

I want to know the difference between 〜がる and 〜がっている, and in what situations I can use them.

My friend said 〜がる is used for a regular activity that someone does every day or every week, and the person also wants to do that activity.

〜がっている is used for activities that someone really wants to do but hardly has time to do.

Is this right?