If we want our application to deal with telephony services on the device then we can do so with the help android.telephony package. In this article, I will show you how to listen for different phone events and take action based upon them. In other words we can make our application react to any phone event such as when the phone rings, signal strength changes, etc. Also, the access to this telephony information of device is permission protected and our application should have appropriate permissions in order to receive device call change updates. So, let's get started!

A status bar notification is a nice way to alert the user about some update from your application, when running in background, specially when you require a response from the user for the same. It adds an icon to the system's status bar along with an optional ticker-text message and an expanded message in the Notifications window. When the user selects the expanded notification message, Android fires an Intent that is defined by the notification which is usually used to launch an Activity. In this article, I will show you how we can implement this notification system in our application.

Whenever the user has to input a date, its always a good idea to assist him/her with a widget which allows the user to select a particular day, month and year.

By default Android provides a widget named DatePicker which can be incoported in your application to provide this functionality to the end users. It has an elegant look and design. So, we will use this widget here.