0Application components are the essential building blocks of an android application. Each component has its own importance. Some of the components have some interface through which user can access the application and some of them have no User interface but they play an important role while running an application as well as during the development.
There are four different types of application components having distinct purpose among themselves and has a distinct life cycle during they created and destroyed.
Here are four components :
1). ACTIVITY
This is the primary classes which provide the graphical user interface to the user and captured the user interaction through that interface. Activity usually implements a single , focused task that user can do like dial a number or opening of browser etc. Activity is the main class user see when they run the application. Activities are designed to provide a graphical user interface or GUI to the user. It enables user to give and receive information to and from an application. Remaining three components has no graphical user interface. Let’s took an example of Whats-app application in which one application shows the recent chats another activity show the contacts available into the Whats App, another one to read the particular chat. Collectively they provide the great user experience.
2). SERVICES
Services are the long running process which runs in the background or to perform a task for a different process. A service has no user interface .e.g. A service might play music in the background while the user in the different application.
3). BROADCAST RECEIVER
Listens to and responds to the events that happen on the device. That event is the system-wide broadcast announcements to which our broadcast receiver responds. Many broadcast systems originate from the systems for e.g. When Image was captured , the battery is low etc.
4). CONTENT PROVIDER
It manages the shared set of application data. You can store your data in the file system , SQLite database , on the web ,on the cloud and you can easily access that data via your application. Through the content provider, other application can query your data or modify if contents provider allows it. Content provider manager is available to manage user contact information.
Building an Android application
Android Build process provides projects and module build setting so that our android application compiled and packed to get .apk. Android build process flow :
Creating an android Application
Creating an android application includes following steps :
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Define the resources
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Implement application classes
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Package Application
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Install and Run Application
1). DEFINE RESOURCES :
Resources are the non-source code entities many different resource types such as layout ,strings , images , menus and animations. Resources allow app to customized for different devices and users.
We can categorize the resources into default and alternative resources. Default resources are those who belongs from device configuration and alternate resources are those which is manually configured apart from the device configuration.
2). IMPLEMENT CLASSES :
Implementation of classes usually involves at least one activity. Activity initialization code usually in onCreate. Now lets us see what's the flow of onCreate :
1. Restore the saved state
2. Set content View
3.Initialise the UI elements
4.Link UI element to code actions
3). PACKAGE THE APPLICATION :
System packages application components and resource into a .APK file. Developer specifies required application information in a specified file name as AndroidManifest.xml.
Android Manifest file includes the all relevant informati
