I have a main activity, that when I click on a button, starts a new activity, i used the following code to do so:
Intent intent = new Intent(this, SettingsAc
You are making this too hard. If I understand what you are trying to do correctly, the built-in 'back' button and Android itself will do all the work for you: http://developer.android.com/guide/components/tasks-and-back-stack.html
Also, implementing a custom "back" button violates Core App Quality Guideline UX-N1: http://developer.android.com/distribute/googleplay/quality/core.html