How to add Activity to manifest.xml in right way?

Question

should I write each activity in android manifest and how? Must each activity have intent-filter, or not?

Answer 1

You must mention each activity in android manifest.

Not all activity need intent filter. intent filters show when to launch this activity. usually you will have one activity with intent filter that is to show that it is first activity when application is launched.

inside application tag in your manifest: