This tutorial explains some of the basic key components of
an Android application, which will be helpful in creating an Android project.
Activities: An activity is a single screen in which a user
interacts in an android application. An application can have more than one
activity. When an application starts it calls the default activity mentioned in
AndroidManifest.xml (Refer HelloWorld example in the previous blog) as
highlighted below, this can be changed at any point of design time.
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
An activity can call / start another activity when required.
Services: Service is the component that is used to perform action
in the background for an application without any user interaction. It can used
for logging or to perform work for remote process.
Content Provider: It’s the standard interface to share data
between processes and provide mechanism for defining data security. Used to
store data in the file system or use SQL Lite. For example using the content
provider the app can read and modify the contact details using the Android
provided content provider.
Broadcast Services: It’s a way to listen to system wide even
happening in your Android device which is accessible to all apps. Some of the
Android provided broadcast services are Screen turned on, battery is low, call/SMS
is received, phone is booted etc.
Intents: It’s a messaging object you can use to request an
action from another component. An Intent is the key component to call one
activity from another activity. For example from our app we can request camera
app to take a picture.
Explicit Intent: Specify the
component to start by name like call another activity in the same app.
Implicit Intent: Does not specify
the component to start instead declare a general action to perform which allows
a component from another app to handle that.
Fragments: Fragment
is the section of the activity which represents the behavior or a portion of user
interface in an activity. An activity can have more than one fragment. A fragment
has its own life cycle which can be removed or added at any point when an
activity is running.
Views: It’s the place
where all the UI elements are being placed in the android application.
Layouts: Layout in Android describes how the UI should look in
an activity. This can be declared in the UI XML and/or instantiate the layout
at runtime. This can be customized as per required. There are various types of
layouts like Linear, Relative, List, Grid etc.
Resources: Resource is a component of the Android application
which is used to keep track of all the non-code assets of the application. Resources
can be a XML file, images, audio files, etc.
