Скачать или смотреть 3. Components of Android App

Components of Android application

building blocks of android app.
these components are declared in the AndroidMenifest.xml file

There are following four main components that can be used within an

Android application

1. Activities
2. Services
3. Broadcast Receivers
4. Content Providers


1. Activities
An activity represents a single screen.
provides a User Interface and also the user interacts with it.

normally consist of two file
one Java file and one xml file(layout)

An activity is implemented as a subclass of Activity class as follows



2. Services
a service is component that runs in the background to perform long

running operations.

for example a service can play music in the background while user is in a

different application.

or it can fetch data from service without blocking the user interface.

A service is implemented as a subclass of Service class as follows -




3.Broadcast Receivers
A broadcast receiver also called receiver is an Android component

which allows you to register for system or application events. All registered

receivers for an event are notified by the Android runtime once this event

happens.

For example, applications can register for the ACTION_BOOT_COMPLETED system

event which is fired once the Android system has completed the boot process.




4.Content Providers


Some other components

Intent
Fragment
View
ViewGroup