Android Software Engineer Interview Preparation Guide

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Android is a stack of software for mobile devices which has Operating System, middleware and some key applications. The application executes within its own process and its own instance of Dalvik Virtual Machine. Many Virtual Machines run efficiently by a DVM device. DVM executes Java language's byte code which later transforms into .dex format files.

Activity provides the user interface. When you create an android application in eclipse through the wizard it asks you the name of the activity. Default name is MainActivity. You can provide any name according to the need. Basically it is a class (MainActivity) that is inherited automatically from Activity class. Mostly, applications have oneor more activities; and the main purpose of an activity is to interact with the user. Activity goes through a numberof stages, known as an activity's life cycle.

In a domain, one or more computer can be a server to manage the network. On the other hand in a workgroup all computers are peers having no control on each other. In a domain, user doesn't need an account to logon on a specific computer if an account is available on the domain. In a work group user needs to have an account for every computer.
In a domain, Computers can be on different local networks. In a work group all computers needs to be a part of the same local network.

Android supports 4 dialog boxes:
★ AlertDialog
★ ProgressDialog
★ DatePickerDialog
★ TimePickerDialog

When we create android application the following folders are created in the package explorer in eclipse which are as follows:
★ src
★ gen
★ assets
★ bin
★ res

SMS messaging is one of the basic and important applications on a mobile phone. Now days every mobile phone has SMS messaging capabilities, and nearly all users of any age know how to send and receive such messages. Mobile phones come with a built-in SMS application that enables you to send and receive SMS messages.

Intent object to activate the built-in Messaging service. You have to pass MIME type "vnd.android-dir/mms-sms", in setType method of Intent as shown in the following given below code.

Intent intent = new Intent (android.content.Intent.ACTION_VIEW);
intent.putExtra("address", "5556; 5558;");// Send the message to multiple recipient.
itent.putExtra("sms_body", "Hello my friends!");
intent.setType("vnd.android-dir/mms-sms");
startActivity(intent);

Take a button on activity_main.xml file as follows.

<Button android:id="@+id/btnSendSMS" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:layout_centerVertical="true" android:onClick="sendmySMS" android:text="sendSMS" />

According to above code when user clicks the button sendmySMS method will be called. sendmySMS is user defined method.

In the AndroidManifest.xml file, add the following statements

<uses-permissionandroid:name="android.permission.SEND_SMS"/>

Now we write the final step. Write the given below method in MainActivity,java file

publicvoidsendmySMS(View v)
{
SmsManagersms = SmsManager.getDefault();
sms.sendTextMessage("5556", null, "Hello from google", null, null);
}
In this example I have used two emulator. On the first Android emulator (5554), click the Send SMSbutton to send an SMS message to the second emulator(5556).

★ An activity Creator is the initial step for creation of a new Android project.
★ It consists of a shell script that is used to create new file system structure required for writing codes in Android IDE.

★ It is Android's virtual machine.
★ It is an interpreter-only virtual machine which executes files in Dalvik Executable (.dex) format. This format is optimized for efficient storage and memory-mappable execution.

AIDL supports following data types:
★ String
★ List
★ Map
★ CharSequence
★ All native Java data types like int,long, char and Boolean

★ AIDL is the abbreviation for Android Interface Definition Language.
★ It handles the interface requirements between a client and a service to communicate at the same level through inter-process communication.
★ The process involves breaking down objects into primitives that are Android understandable.

Android Architecture consists of 4 key components:
★ Linux Kernel
★ Libraries
★ Android Framework
★ Android Applications

★ Storing the information about number of visitors (counter).
★ Storing the date and time (when your Application is updated).
★ Storing the username and password.
Storing the user settings.

Different data storage options are available in Android are:
★ SharedPreferences
★ SQlite
★ ContentProvider
★ File Storage
★ Cloud Storage

★ It contains the package name of the application.
★ The version code of the application is 1.This value is used to identify the version number of your application.
★ The version name of the application is 1.0
★ The android:minSdkVersion attribute of the element defines the minimum version of the OS on which the application will run.
★ ic_launcher.png is the default image that located in the drawable folders.
★ app_name defines the name of applicationand available in the strings.xml file.
★ It also contains the information about the activity. Its name is same as the application name.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.globalguideline" android:versionCode="1" android:versionName="1.0">

<uses-sdk android:minSdkVersion="8" android:targetSdkVersion="18" />

<application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme">

<activity android:name="com.example.globalguideline.MainActivity" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

</manifest>

src Contains the .java source files for your project. You write the code for your application in this file. This file is available under the package name for your project.

It contains the .apk file (Android Package) that is generated by the ADT during the build process. An .apk file is the application binary file. It contains everything needed to run an Android application.

This folder contains all the information about HTML file, text files, databases, etc.

This folder contains android.jar file, which contains all the class libraries needed for an Android application.

This folder contains the R.java file. It is compiler-generated file that references all the resources found in your project. You should not modify this file.

This folder contains all the resource file that is used byandroid application. It contains subfolders as: drawable, menu, layout, and values etc.

An alert dialog box supports 0 to 3 buttons and a list of select-able elements, including check boxes and radio buttons. Among the other dialog boxes, the most suggested dialog box is the alert dialog box.

This dialog box displays a progress wheel or a progress bar. It is an extension of AlertDialog and supports adding buttons.