We need to understand views, activities, fragments, intents, content providers,
services, and the AndroidManifest.xml file when you build applications for Android.
Views are user interface (UI) elements that form the basic building blocks of a user interface.
A view can be a button, a label, a text field, or many other UI elements.
Views are also used as containers for views, which means there's usually a hierarchy of views in the UI.
An activity is a UI concept that usually represents a single screen.
It generally contains one or more views.
Fragments are like sub-activities, and an activity can display one or more fragments on the screen at the same time.
When a screen is small, an activity is more likely to contain just one fragment, and that fragment can be the same one used within larger screens.
An intent generically defines an "intention" to do some work.
Intents encapsulate several concepts. We can use intents to perform the following tasks:
Intents are not always initiated by your application.
Intents are also used by the system to notify your application of specific events, such as the arrival of a text message.
Intents can be explicit or implicit. If you simply say that you want to display a URL, the system decides what component will fulfill the intention.
We can also provide specific information about what should handle the intention.
Intents loosely couple the action and action handler.
Android defines a standard way for applications to share data without exposing the underlying storage.
Through content providers, you can expose your data and have your applications use data from other applications.
Services in Android resemble services you see in Windows or other platforms.
Services are background processes that can run for a long time.
Android defines two types of services:
Local services are only accessible by the application that is hosting the service.
Remote services are services that are meant to be accessed remotely by other applications running on the device.