It took 3 days to complete this app and finally I completed it today. I included functions like registering as a new user, login and reset the password. To avoid logging in the app everytime when the user open, I used isValidate function so that the user can directed to the contact list without re-entering the password.
Previous time, while on learning, I used list view to display the list of contact. But for this time, I used Recycler view. When we click on any contact, it prompts to the new activity where you can make call or send email or delete or edit.
Every changes made in the app is reflected to the online database. So the contacts can be recovered even when the mobile is lost or reset.
Chandru's blog 