Develop a ‘Hello Android’ Application

Contributed by Asad Khan

The Java core Libraries includes all the collection classes, utilities, I/O etc that you have been using in the J2SE implementation of Java apart from Swing & other AWT classes.

Just below the applications lie the Application Framework, it is the toolkit that almost all Android applications use. Activity manager manages the lifecycle of the applications. Package manager keeps track of all applications that have been installed on the device. The window manager manages windows and is basically a wrapper on top of lower level services provided by the surface manager. Telephony manager provides support for telephony related features.

Content manager allows for the applications to share their data with other applications. Resource manager handles all the resources related to your app, anything that isn’t code is handled by resource manager. View system consists of UI elements which also handles things like event dispatching layout, drawing etc. Location manager is used to provide geographic related data to the device. For example you can register an intent with the location manager to notify you when you get close to a point.

Notification manager allows any application to put notification onto the status bar to alert the user about any interesting event. XMPP allows application to send device-to-device data messages to other android users.

The Android UI

The Android UI framework is in par with the cutting edge UI frameworks available today like JavaFX or Microsoft Silverlight. The entire interface even the animations can be declared in the XML files.

Screens or windows in Android are referred to as activities that can consist of multiple views. Views are basic building blocks in Android. A View occupies a rectangular area on the screen and is responsible for drawing and event handling. View is the base class for widgets, which are used to create interactive UI components (buttons, text fields, etc.).

Android Application Foundations

Activity

Activity represents a single screen in your application; it contains one or more views.

Intent

Intent is an intention to so some work like for examplean applications intent to dial a phone number, to launch an activity or to start a service. Intents are not always initiated by your application, they can be used by a system to notify your application that a certain event has occurred for example, arrival of a text message or a phone call.

Service

Services in Android are background tasks that can run potentially for longer periods. There are two types of services on Android local and remote.

Local services are only accessible to the application that is hosting the service and remote services are meant to be used by other applications running on the device. An example of service could be a music player, which keeps on running in the background.

Content Provider

Enables apps to share data across the apps on the device. If you want to access the address book you would ask content provider for it.

With all the info under our belt let’s quickly develop a small Hello Android application. Follow the instructions below

• Download the eclipse IDE from http://www.eclipse.org/downloads/. Unzip & install it on your system.
• Download a copy of Android SDK from http://developer.android.com/sdk/index.html. Unzip it & place it in your home directory or where ever you like.
• Add the location of your SDK directory location to your PATH. On Linux I had to edit ~/.bash.rc by appending this text “export PATH={PATH}:~/android-sdk-linux_86/tools”. Just enter command vi ~/.bashrc, scroll to the end & paste the export statement above by first pressing “i” to enter the insert mode press escape to exit insert mode & then write “:wq” to write ie save & quit the vi editor.
• Fire up Eclipse go to help menu click on Software Updates add a new site in Available software’s https://dl-ssl.google.com/android/eclipse/
• Restart Eclipse.
• Go to window preferences & in Android preferences add the location of your SDK.
• Use the Android SDK and AVD Manager, included in the SDK starter package, to add one or more Android platforms. Use this page as a reference if you’re unsure http://developer.android.com/sdk/adding-components.html.
• After that go to File menu -> New and click on the Android project.

Hope you enjoyed reading this post

About The Author

“Asad Khan is the CEO & Co-Founder of Semantic Notion. He first started programming on his Commodore 64 & has never looked back since. He is a serial entrepreneur. His first successful tech start-up was at the age 16. Currently, he is leading a small start-up which specializes in intelligent web solutions.  ”