Android components

Understand these basics before moving forward

1. Intent : In android an intent describes what you want to do. Like opening a web page or access a contact record. It facilitates navigation in an Android system.

An Intent is a declaration of need. It’s made up of a number of pieces of information that describe the desired action or service.

 2. IntentFilter :They are the declaration of capabilities, They are defined in   AndroidManifest.xml. When an intent is created, its appropriate IntentFilter is searched for in the AndroidManifest.xml and hence navigation forwarded to that IntentFilter.

An IntentFilter is a declaration of capability and interest in offering assistance to those in need. It can be generic or specific with respect to which Intents it offers to service.

3. Activity : Directly related to the UI.It is the class that handles events/requests from UI. If your application has a UI, it’ll have at least one Activity. It is like the controller in the MVC pattern.

4. Service : Long running operations are placed into services. Nothing to do with UI. Ex: running some background processing of data etc. 

5. BroadcastReceiver : They receive global events like phone ringing or incoming SMSes. Like services they do not have UIs. They are not suppose to be heavy or long running code like in services.

6. ContentProvider : If an application needs to expose some data from a backend, it needs to use the ContentProvider. 

ContentProvider is the interface for the underlying data. Data can be in the form of a file or stored in a backend database.

7. AndroidManifest.xml : It is the deployment descriptor of the applications.