Exibir código-fonte para Os 4 tipos de componentes

; '''Activities'''
An ''activity'' represents a single<nowiki> </nowiki>screen with a user interface. For example, an email application might 
have one activity that shows a list of new emails, another activity to 
compose an email, and another activity for reading emails. Although the 
activities work together to form a cohesive user experience in the email
<nowiki> </nowiki>application, each one is independent of the others. As such, a 
different application can start any one of these activities (if the 
email application allows it). For example, a camera application can 
start the activity in the email application that composes new mail, in 
order for the user to share a picture.
An activity is implemented as a subclass of <code>Activity</code> and you can learn more about it in the Activities developer guide.
; '''Services'''
A ''service'' is a component that runs in the background to perform long-running operations or to perform 
work for remote processes. A service does not provide a user interface. 
For example, a service might play music in the background while the user
<nowiki> </nowiki>is in a different application, or it might fetch data over the network 
without blocking user interaction with an activity. Another component, 
such as an activity, can start the service and let it run or bind to it 
in order to interact with it. 
A service is implemented as a subclass of <code>Service</code> and you can learn more about it in the Services developer guide.
; '''Content providers'''
A ''content provider'' manages a shared set of application data. You can store the data in the 
file system, an SQLite database, on the web, or any other persistent 
storage location your application can access. Through the content 
provider, other applications can query or even modify the data (if the 
content provider allows it). For example, the Android system provides a 
content provider that manages the user's contact information. As such, 
any application with the proper permissions can query part of the 
content provider (such as <code>ContactsContract.Data</code>) to read and write information about a particular person. 
Content providers are also useful for reading and writing data that 
is private to your application and not shared. For example, the Note Pad sample application uses a content provider to save notes.

A content provider is implemented as a subclass of <code>ContentProvider</code>and must implement a standard set of APIs that enable other 

applications to perform transactions. For more information, see the Content Providers developer guide.
; '''Broadcast receivers'''
A ''broadcast receiver'' is a component that responds to system-wide broadcast announcements.  
Many broadcasts originate from the system—for example, a broadcast 
announcing that the screen has turned off, the battery is low, or a 
picture was captured. Applications can also initiate broadcasts—for 
example, to let other applications know that some data has been 
downloaded to the device and is available for them to use. Although 
broadcast receivers don't display a user interface, they may create a status bar notification
<nowiki> </nowiki>to alert the user when a broadcast event occurs. More commonly, though,
<nowiki> </nowiki>a broadcast receiver is just a "gateway" to other components and is 
intended to do a very minimal amount of work. For instance, it might 
initiate a service to perform some work based on the event. 
A broadcast receiver is implemented as a subclass of <code>BroadcastReceiver</code> and each broadcast is delivered as an <code>Intent</code> object. For more information, see the <code>BroadcastReceiver</code> class.
[[Categoria:Android]]