android+building+blocks.ppt
DESCRIPTION
Android building blocksTRANSCRIPT
Android Components
Vivek Nadar
Application ComponentsApplication Components
There are 4 types of application components
(1) Activities – visual user interface focused
on a single thing a user can do
(2) Services – no visual interface –
they run in the background
(3) Broadcast Receivers –
receive and react to broadcast announcements
(4) Content Providers –
allow data exchange between applications
What is an Activity ? An Activity means a single screen with a user interface. An application usually consists of multiple activities
that are loosely bound to each other. Activity generally provides a user with an interactive screen to do
something like:
Dialing the phone, Viewing a map, etc. Every screen in an application,is an activity by itself.
Intents
Intents are used as a message-passing mechanism, that works both within application and between applications.
Two types of Intents:
1) Implicit Implicit does not specify a component. Instead,it includes enough information for
the system to determine which of the available components is best to run for that intent.
Example : Intent webIntent = new
Intent(Intent.ACTION_VIEW,Uri.parse("http://www.google.com")); startActivity(webIntent);
Intents...(2)2) Explicit Intents
Explicit Intents explicitly defines the component which should be called by the Android system, by using the Java class as identifier.
e.g. Intent launchExplicitIntent = new Intent(this,Game.class);
startActivity(launchExplicitIntent);
Program Demo
2. Services A Task that runs in the background without the user's direct interaction. A service does not have a visual user interface. A service,by default runs in the main thread of the application
that hosts it. Examples
Network Downloads Playing Music Checking updates for an application
Program Demo
3. Broadcast receiver
A Broadcast receiver is a component that responds to system-wide Broadcast announcements.
Many broadcasts originate from the system - for e.g. a Broadcast announcing that thescreen has turned off, the battery is low,a picture was captured or an SMS is received.
Broadcast receiver...(2)
An Application can also initiate broadcast
for e.g.to let other Applications know that
some data has been downloaded to the device
and is available for those application to use.
It creates a status bar notification to alert the user when a broadcast event occurs.
4. Content Providers
Shared set of data. Makes some of the application data
available to other applications It is the only way to transfer data between applications in
Android (no shared files,
no shared memory,no pipes, etc.)