By Dr. Anu Sahni

anu.sahni@ncirl.ie

1. Why Android2. Introduction – What is Android3. Introduction – More about Android4. Android Devices5. Android versions 6. Android Architecture7. Example 1 – Running “Hello World” on Emulator and device

i. Creating first project “Hello World”ii. Running “Hello World” on Emulatoriii. Running “Hello World” on real device

8. Anatomy of Android Application

Note: All the names and examples are for illustration purpose only and should be replaced according to your environment.

The most recent data from IDC shows that for Q3 of 2013 Android made up 81 percent of devices shipped with Samsung making 53 percent of the profit for the quarter

Apple’s iOS scraped by with a sad and distant second place figure of only 12.9 percent with 56 percent of the profit in the mobile device market

HTC, LG, Motorola, Nokia, and BlackBerry lost money

Apple leads Android in enterprise adoption, and in retail shopping use by consumers

The volume of apps available in the Google Play app store has caught up to Apple, and Android is winning in app downloads as well. Google reportedly comprises 75 percent of all app downloads, compared to only 18 percent for Apple.

Android is a mobile operating system based on modified version of Linux

Open and free under Apache License

• Developers have access to the source code

• Vendors (Samsung, Motorola, Sony Ericsson) can add propriety extensions

• Same program runs on different devices running Android

No fixed hardware and software as manufactures can customise freely

• Storage – uses SQLite for database

• Connectivity – Android provides rich APIs to let your app connect and interact with other devices over Bluetooth, NFC, Wi-Fi P2P, USB, and SIP, in addition to standard network connections.

• Web browser – based on open-source WebKit with Chrome V8 JavaScript engine

• Media – supports

H.264, AAC and HE-AAC (in 3GP or MP4 container)

MP3, MIDI, Ogg Vorbis

Wav - compatible with Windows, Macintosh, and Linux operating systems

JPEG, PNG, GIF, BMP

• Hardware support – Accelerometer Sensor, Camera, Digital Compass, Proximity Sensor, and GPS

• Multi-touch – supports multi-touch screens

• Multi-tasking – supports multi-tasking apps

• Tethering – supports Internet connections sharing such as wired/wireless hotspot

Smartphones Tablets E-reader devicesNotebookMP4 playersAndroid TV

Version Codename API Distribution

2.2 Froyo 8 1.6%

2.3.3 -2.3.7

Gingerbread 10 24.1%

3.2 Honeycomb 13 0.1%

4.0.3 -4.0.4

Ice Cream Sandwich

15 18.6%

4.1.x

Jelly Bean

16 37.4%

4.2.x 17 12.9%

4.3 18 4.2%

4.4 KitKat 19 1.1%

Linux Kernel (layer 1): contains all low-level device drivers for Android hardware components

Libraries (layer 2): contains code for the main features provided by Android OS. For example SQLite library for database support and WebKit library for web browsing feature

Android runtime (layer 2): contains core libraries to enable developers to write codes in Java. Also includes Dalvik virtual machine, designed specifically for Android and optimised for battery powered mobile devices with limited memory and CPU. All apps are compiled into Dalvik exe

Application Framework: exposes various capabilities of Android OS to enable developers to include them in their apps such as camera

Applications: contains apps that come with the device such as Phone, Contacts, Browser and all the 3rd party apps that you install.

Launch Eclipse Click New in the

toolbar. In the window that

appears, open the Android folder if it is not already open , select Android Application Project, and click Next as shown in Figure 1.

Figure 1. The New Android App Project wizard in Eclipse.

Fill in the form that appears: Application Name is the app name

that appears to users. For this project, use “Hello World."

Project Name is the name of your project directory and the name visible in Eclipse.

Package Name is the package namespace for your app that must be unique across all packages installed on the Android system. Common practice is to use the name in reverse order - domain name of your organization first followed by the project name. For example, "com.example.helloworld“.

Read the warning.

Read the comment.Figure 1. The New Android App Project wizard in Eclipse.

Minimum Required SDK is the lowest version of Android that your app supports, indicated using the API level. 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. 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.

Figure 1. The New Android App Project wizard in Eclipse.

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.

Theme specifies the Android UI style to apply for your app. You can leave this alone.

Click Next.

Figure 1. The New Android App Project wizard in Eclipse.

On the next screen to configure the project, leave the default selections and click Next.

The next screen can help you create a launcher icon for your app. Click Next.

Select BlankActivity as your activity template and click Next.

Leave all the details for the activity in their default state and click Finish.

An Android Virtual Device (AVD) is a device configuration for the Android emulator that allows you to model different devices.

Follow the steps below to create an AVD: Launch the Android Virtual Device Manager – Window Android Virtual

Device Manager .

In the Android Virtual Device Manager panel, click New.

Fill in the details for the AVD. Give it a name, a platform target, an SD card size, and a skin (HVGA is default).

Click Ok.Select the new AVD from the Android Virtual Device

Manager and click Start.Starting Android Emulator window starts the emulator,

AVD2 in this case.Close the Starting Android Emulator window after the

emulator shows up.

Once the AVD is created, select the Project name and click Run As… from the toolbar.

Select Android Application and click OK.

Select the AVD on which you want to run the app

Launch Hello World

Plug in your device to your development machine with a USB cable.

Install the appropriate USB driver for your device. Enable USB debugging on your device. On most devices running Android 3.2 or older, you can find

the option under Settings Applications Development.

On Android 4.0 and newer, it's in Settings Developer options.

On Android 4.2 and newer, Developer options is hidden by default. To make it available, go to Settings About phone and tap Build number seven times. Return to the previous screen to find Developer options.

Run the app from Eclipse:

Right click the project and select Run As Run Configurations…

Select Launch on all compatible devices/AVD’s

Select Active devices from the dropdown

Click Run

All apps are created as projects. Folders and files that make up an

Android project:src: contains the .java source files for your

project. For example, MainActivity.java is the source file of the main activity of the app. Unlike Java programs that have entry only through the main method, an Android activity may have more than 1 entry points. For example, you can call Camera app from your app resulting an additional entry point for the Camera app

gen: contains config file and R.java. R.java is a compiler generated file and contains the references to all the resources in project.

Note 1: Don’t modify R.java.Note 2: as you add more files and folders to your project, Eclipse automatically generates the contents of R.java. Note 3: if you accidently delete R.java, Eclipse will regenerate it for you immediately provided there are no errors.

Android 4.2: contains android.jar, which contains all the class libraries used for project. For example, security, opengl, accessibility, animation, etc.

Android Dependencies: contains JAR files your project depends on and the assets folder. For example, the Support Package includes static "support libraries" that you can add to your Android application in order to use APIs that are either not available for older platform versions or that offer "utility" APIs that aren't a part of the framework APIs. The goal is to simplify your development by offering more APIs that you can bundle with your application so you can worry less about platform versions.

assets: contains all the assets used by the project such as HTML, database.

bin: During the build process, your Android projects are compiled and packaged into an .apk file, the container for your application binary. It contains all of the information necessary to run your application on a device or emulator, such as compiled .dex files (.class files converted to Dalvik byte code), a binary version of the AndroidManifest.xml file, compiled resources (resources.arsc) and uncompiled resource files for your application. The ADT plugin incrementally builds your project as you make changes to the source code. Eclipse outputs an .apk file automatically to the bin folder of the project, so you do not have to do anything extra to generate the .apk.

libs: contains all Java libraries that can be packaged and distributed using the Java Archive Format (also called JAR). There are a number of Android-compatible libraries that can be leveraged within your Android applications provided they are linked properly to your project . Theses JAR files are automatically picked by Eclipse. For example package, android-support-v4.jar.

res: contains all the resources used by the project plus a few subfolders such as drawable -<resolution>, layout, and values.

AndroidManifest.xml: The manifest file describes the fundamental characteristics of the app and defines each of its components. You specify all the permissions needed by your app, as well as other features such as Intents.

This file contains the following: Package name Version code, app version, such as 1. Version name of the app such as 1.0.

The format should be x.y.z. <uses-sdk> : This declares your app's

compatibility with different Android versions using the android:minSdkVersion and android:targetSdkVersion attributes -▪ android:minSdkVersion — Specifies the

minimum API Level on which the application is able to run. The default value is "1".

▪ android:targetSdkVersion — Specifies the API Level on which the application is designed to run. It should be set as high as possible.

▪ App details Icon image: uses the image for icon, for

example ic_launcher.png in the drawablefolder.

Name of the app – the app name specified with the variable name app_name in the string.xml file. The app name is My First App.

Activities: there are two activities in the app - MainActivity The label displayed for this activity is the same as the app name and DisplayMessageActivity.

intent-filters: are contained within the definitions of activities.

The action for the intent-filter is named android.intent.action.MAIN means that this activity is the main entry point for the app.

The category android.intent.category.LAUNCHER indicates that the app can be launched from the device icon launcher.

Finally the code that connects the activity to the UI (main.xml) is the setContentView() method in MainActivity.java file.

package com.example.myfirstapp;

import android.os.Bundle;import android.app.Activity;

public class MainActivity extends Activity {

@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main); }}

Here, R.layout.activity_main refers to the activity_main.xml file in the res/layout folder.

The onCreate() method is one of the many methods that are fired when an activity is loaded.

Note 2: as you add more XML files to the res/layout folder, the file names are automatically generated in R.java.

Thank youanu.sahni@ncirl.ie