title: call a method in the main Activity. From a Custom View class
body: <p>i am using the following method in a new application i'm developing.</p>
  
  <p>there is a main activity, which instantiates different classes that extends RelativeLayout, and i'm using setContentView to switch between the different modules of the application.</p>
  
  <p>i wonder if this is a good approach or necesarily i have to use different activities to the several screens the app haves.</p>