[Android] [Java] How to handle unexpected activity

I’m new to Appium and I’m using it for my automation testing with my Android app.
My app is similar to a phone app, it has 2 activities, one is the main activity the other only shows up when there’s a call from another phone (using the same app).
The question is: How can I control the second activity?
As what I can understand so far, I can only control the activity which I declare as “appActivity” in the DesireCapability.
Very appreciate for any help you guys can give me!

Can anybody help me plzz!!!

You can start the second activity by calling it from the code explicitly.

driver.startActivity(<activity name>);

Make sure that the activity is launch-able.