Android Development Guide

1. What is Android?

                 Android is an operating system based on the Linux kernel, and designed primarily for touchscreen mobile devices such as smartphones and tablet computers. Initially developed by Android, Inc., which Google backed financially and later bought in 2005, Android was unveiled in 2007 along with the founding of the Open Handset Alliance—​a consortium of hardware, software, and telecommunication companies devoted to advancing open standards for mobile devices.
                 Android is a Linux-based software system, and similar to Linux, is free and open source software. This means that other companies can use the Android operating system developed by Google and use it in their mobile devices (more on that later). The distinguishing factor of this brand is a kernel. Android hosts a central core, which essentially is a strip code that helps the software operate.

2. Development Tools for Android?

           If you're a new Android developer, we recommend you download the ADT Bundle to quickly start developing apps. It includes the essential Android SDK components and a version of the Eclipse IDE with built-in ADT (Android Developer Tools) to streamline your Android app development.

With a single download, the ADT Bundle includes everything you need to begin developing apps:

• Eclipse + ADT plugin
• Android SDK Tools
• Android Platform-tools
• The latest Android platform
• The latest Android system image for the emulator

They provide ADT Bundle for different platforms like Windows, Mac, Linux. You can Download the Android SDK from here

3. Android Installation Guide?

           

1. Unpack the ZIP file (named adt-bundle-windows-x86-20140321) and save it to an appropriate location, such as a "AndroidDevelopment" directory in your home directory.
2. Open the AndroidDevelopment/adt-bundle-windows-x86-20140321/eclipse directory and launch eclipse.

That's it! The IDE is already loaded with the Android Developer Tools plugin and the SDK is ready to go. To start developing, read Building Your First App.

4. Android Eclipse Folder Structure?

Android projects are the projects that eventually get built into an .apk file that you install onto a device. They contain things such as application source code and resource files. Some are generated for you by default, while others should be created if required. The following directories and files comprise an Android project:

src/

Contains your stub Activity file, which is stored at src/your/package/namespace/ActivityName.java. All other source code files (such as .java or .aidl files) go here as well.

bin/

Output directory of the build. This is where you can find the final .apk file and other compiled resources.

jni/

Contains native code sources developed using the Android NDK. For more information, see the Android NDK documentation.

gen/

Contains the Java files generated by ADT, such as your R.java file and interfaces created from AIDL files.

assets/

This is empty. You can use it to store raw asset files. Files that you save here are compiled into an .apk file as-is, and the original filename is preserved. You can navigate this directory in the same way as a typical file system using URIs and read files as a stream of bytes using the AssetManager. For example, this is a good location for textures and game data.

res/

Contains application resources, such as drawable files, layout files, and string values. See Application Resources for more information.

anim/

For XML files that are compiled into animation objects. See the Animation resource type.

color/

For XML files that describe colors. See the Color Values resource type.

drawable/

For bitmap files (PNG, JPEG, or GIF), 9-Patch image files, and XML files that describe Drawable shapes or Drawable objects that contain multiple states (normal, pressed, or focused). See the Drawable resource type.

layout/

XML files that are compiled into screen layouts (or part of a screen). See the Layout resource type.

menu/

For XML files that define application menus. See the Menus resource type.

raw/

For arbitrary raw asset files. Saving asset files here instead of in the assets/ directory only differs in the way that you access them. These files are processed by aapt and must be referenced from the application using a resource identifier in the R class. For example, this is a good place for media, such as MP3 or Ogg files.

values/

For XML files that are compiled into many kinds of resource. Unlike other resources in the res/ directory, resources written to XML files in this folder are not referenced by the file name. Instead, the XML element type controls how the resources is defined within them are placed into the R class.

xml/

For miscellaneous XML files that configure application components. For example, an XML file that defines aPreferenceScreen, AppWidgetProviderInfo, or Searchability Metadata. See Application Resources for more information about configuring these application components.

libs/

Contains private libraries.

AndroidManifest.xml

The control file that describes the nature of the application and each of its components. For instance, it describes: certain qualities about the activities, services, intent receivers, and content providers; what permissions are requested; what external libraries are needed; what device features are required, what API Levels are supported or required; and others. See the AndroidManifest.xml documentation for more information

project.properties

This file contains project settings, such as the build target. This file is integral to the project, so maintain it in a source revision control system. To edit project properties in Eclipse, right-click the project folder and selectProperties.

local.properties

Customizable computer-specific properties for the build system. If you use Ant to build the project, this contains the path to the SDK installation. Because the content of the file is specific to the local installation of the SDK, thelocal.properties should not be maintained in a source revision control system. If you use Eclipse, this file is not used.

ant.properties

Customizable properties for the build system. You can edit this file to override default build settings used by Ant and also provide the location of your keystore and key alias so that the build tools can sign your application when building in release mode. This file is integral to the project, so maintain it in a source revision control system. If you use Eclipse, this file is not used.

build.xml

The Ant build file for your project. This is only applicable for projects that you build with Ant.

5. Creating  A New Application On Eclipse?

1. Click New  in the toolbar.
2. In the window that appears, open the Android folder, select Android Application Project, and click Next.

Figure 1. The New Android App Project wizard in Eclipse.
3. Fill in the form that appears:
   • Application Name is the app name that appears to users. For this project, use "My First App."
   • Project Name is the name of your project directory and the name visible in Eclipse.
   • Package Name is the package namespace for your app (following the same rules as packages in the Java programming language). Your package name must be unique across all packages installed on the Android system. For this reason, it's generally best if you use a name that begins with the reverse domain name of your organization or publisher entity. For this project, you can use something like "com.example.myfirstapp." However, you cannot publish your app on Google Play using the "com.example" namespace.
   • Minimum Required SDK is the lowest version of Android that your app supports, indicated using the API level. To support as many devices as possible, you should set this to the lowest version available that allows your app to provide its core feature set. If any feature of your app is possible only on newer versions of Android and it's not critical to the app's core feature set, you can enable the feature only when running on the versions that support it (as discussed in Supporting Different Platform Versions). Leave this set to the default value for this project.
   • Target SDK indicates the highest version of Android (also using the API level) with which you have tested with your application.
     As new versions of Android become available, you should test your app on the new version and update this value to match the latest API level in order to take advantage of new platform features.
   • Compile With is the platform version against which you will compile your app. By default, this is set to the latest version of Android available in your SDK. (It should be Android 4.1 or greater; if you don't have such a version available, you must install one using the SDK Manager). You can still build your app to support older versions, but setting the build target to the latest version allows you to enable new features and optimize your app for a great user experience on the latest devices.
   • Theme specifies the Android UI style to apply for your app. You can leave this alone.
   Click Next.
4. On the next screen to configure the project, leave the default selections and click Next.
5. The next screen can help you create a launcher icon for your app.
   You can customize an icon in several ways and the tool generates an icon for all screen densities. Before you publish your app, you should be sure your icon meets the specifications defined in the Iconography design guide.
   Click Next.
6. Now you can select an activity template from which to begin building your app.
   For this project, select BlankActivity and click Next.
7. Leave all the details for the activity in their default state and click Finish.

6. How  to Run The  Android Application?

1.Create Android Virtual Device

          Define a new Android Virtual Device (AVD) by opening the AVD Manager via Window → Android Virtual Device Manager and by pressing the New button.

1. In the Android Virtual Device Manager panel, click New.
2. Fill in the details for the AVD. Give it a name, a platform target, an SD card size, and a skin (HVGA is default).
3. Click Create AVD.
4. Select the new AVD from the Android Virtual Device Manager and click Start.
5. After the emulator boots up, unlock the emulator screen.

To run the app from Eclipse:

1. Open one of your project's files and click Run  from the toolbar.
2. In the Run as window that appears, select Android Application and click OK.

7. Android Basic Components

                 7.1. Activity

                 7.2. BroadCast Reciever

                 7.3. Service

                 7.4. Content Provider

7.1.Activity

An activity is the visual representation of an Android application. An Android application can have several activities.

Activities use views and fragments to create the user interface and to interact with the user. Both elements are described in the next sections.

7.2. BroadcastReceiver

A broadcast receiver (receiver) can be registered to listen to system messages and intents. A receiver gets notified by the Android system if the specified event occurs.

For example, you can register a receiver for the event that the Android system finished the boot process. Or you can register for the event that the state of the phone changes, e.g., someone is calling.

7.3. Service

A service performs tasks without providing an user interface. They can communicate with other Android components, for example, via broadcast receivers and notify the user via the notification framework in Android.

7.4. ContentProvider

A content provider (provider) defines a structured interface to application data. A provider can be used for accessing data within one application, but can also be used to share data with other applications.

Android contains an SQLite database which is frequently used in conjunction with a content provider. The SQLite database would store the data, which would be accessed via the provider.