Android Interview Questions and Answers

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Android is an operating system for mobile devices that includes middleware and key applications, and uses a modified version of the Linux kernel. It was initially developed by Android Inc..It allows developers to write managed code in the Java language, controlling the device via Google-developed Java libraries…..
The Android SDK includes a comprehensive set of development tools . These include a debugger, libraries, a handset emulator (based on QEMU), documentation, sample code, and tutorials. Currently supported development platforms include x86-architecture computers running Linux (any modern desktop Linux distribution), Mac OS X 10.4.8 or later, Windows XP or Vista.

 
Android does not use established Java standards, i.e. Java SE and ME. This prevents compatibility among Java applications written for those platforms and those for the Android platform. Android only reuses the Java language syntax, but does not provide the full-class libraries and APIs bundled with Java SE or ME.

What is android?
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 languages byte code which later transforms into .dex format files.

Why to use Android?

Android is useful because: It is simple and powerful SDK Licensing, Distribution or Development fee is not required Easy to Import third party Java library Supporting platforms are – Linux, Mac Os Windows.

What is localization and how to achieve?

Localization is a way of representing the products in different languages. Android is an operating system which runs in many regions, so to reach different users localization is a must. Localization in Android can be achieved by incorporating different languages in the application which you are using. To do this knowledge of Java, XML elements, Activity life cycle and general principles of internationalization and localization are required.

What are the advantages of Android?

The following are the advantages of Android:

* Innovative products like the location-aware services, location of a nearby convenience store etc., are some of the additive facilities in Android.

Components can be reused and replaced by the application framework.

*Optimized DVM for mobile devices

*SQLite enables to store the data in a structured manner.

*Supports GSM telephone and Bluetooth, WiFi, 3G and EDGE technologies

*The development is a combination of a device emulator, debugging tools, memory profiling and plug-in for Eclipse IDE.

* The customer will be benefited from wide range of mobile applications to choose, since the monopoly of wireless carriers like AT&T and Orange will be broken by Google Android.

* Features like weather details, live RSS feeds, opening screen, icon on the opening screen can be customized.

The customer will be benefited from wide range of mobile applications to choose, since the monopoly of wireless carriers like AT&T and Orange will be broken by Google Android.

Features like weather details, live RSS feeds, opening screen, icon on the opening screen can be customized

Innovative products like the location-aware services, location of a nearby convenience store etc are some of the additive facilities in Android.

Features of Android : 

• Components can be reused and replaced by the application framework.
• Optimized DVM for mobile devices 
• SQLite enables to store the data in a structured manner. 
• Supports GSM telephone and Bluetooth, WiFi, 3G and EDGE technologies.
•  The development is a combination of a device emulator, debugging tools, memory profiling and plug-in for Eclipse IDE. 
• Media support Application framework Optimized graphics Integrated browser 

Describe Android Application Architecture.

Android Application Architecture has the following components:

Services – like Network Operation

Intent - To perform inter-communication between activities or services

Resource Externalization - such as strings and graphics

Notification signaling users - light, sound, icon, notification, dialog etc.

Content Providers - They share data between applications

What kinds of devices can be Android compatible?
The Android software can be ported to a lot of different kinds of devices, including some on which third-party apps won’t run properly. The Android Compatibility Definition Document (CDD) spells out the specific device configurations that will be considered compatible.
For example, though the Android source code could be ported to run on a phone that doesn’t have a camera, the CDD requires that in order to be compatible, all phones must have a camera. This allows developers to rely on a consistent set of capabilities when writing their apps.
The CDD will evolve over time to reflect market realities. For instance, the 1.6 CDD only allows cell phones, but the 2.1 CDD allows devices to omit telephony hardware, allowing for non-phone devices such as tablet-style music players to be compatible. As we make these changes, we will also augment Android Market to allow developers to retain control over where their apps are available. To continue the telephony example, an app that manages SMS text messages would not be useful on a media player, so Android Market allows the developer to restrict that app exclusively to phone devices.
If my device is compatible, does it automatically have access to Android Market and branding?
Android Market is a service operated by Google. Achieving compatibility is a prerequisite for obtaining access to the Android Market software and branding. Device manufacturers should contact Google to obtain access to Android Market.

Is compatibility mandatory?
No. The Android Compatibility Program is optional. Since the Android source code is open, anyone can use it to build any kind of device. However, if a manufacturer wishes to use the Android name with their product, or wants access to Android Market, they must first demonstrate that the device is compatible.

 

Why did we open the Android source code?

Google started the Android project in response to our own experiences launching mobile apps. We wanted to make sure that there would always be an open platform available for carriers, OEMs, and developers to use to make their innovative ideas a reality. We also wanted to make sure that there was no central point of failure, so that no single industry player could restrict or control the innovations of any other. The single most important goal of the Android Open-Source Project (AOSP) is to make sure that the open-source Android software is implemented as widely and compatibly as possible, to everyone’s benefit.
You can find more information on this topic at our Project Philosophy page.

 

How many ways data stored in android?

Shared preferences

Internal storage

External storage

Sqlite database

Network connetion

User interface types?

Views

Notifications

Types of notification in android?

Tost notification

Status bar notification

Dialog notification

How do you find any view element into your program?

Findviewbyid().

What is handler class do in android?

Handler allows you to send and process message and runnable objects associated with a thread’s message queue.

How do you declare 4 components of android in mainfestfile?

<activity>

<service>

<receiver>

<provider>

What are intent filters?

Intents filter are used to register activity, services, broadcast receiver as being capable of performing an action on a particular kind of action.

Describe the APK format. 

The APK file is compressed the AndroidManifest.xml file, application code (.dex files), resource files, and other files. A project is compiled into a single .apk file.  

What is an action? 
The Intent Sender desires something or doing some task .

What is activity? 
A single screen in an application, with supporting Java code.

What is intent in Android? 
A class (Intent) will describes what a caller desires to do. The caller will send this intent to Android's intent resolver, which finds the most suitable activity for the intent. E.g. opening a PDF document is an intent, and the Adobe Reader apps will be the perfect activity for that intent(class).

What is a Sticky Intent? 
sendStickyBroadcast() performs a sendBroadcast (Intent) known as sticky, i.e. the Intent you are sending stays around after the broadcast is complete, so that others can quickly retrieve that data through the return value of registerReceiver (BroadcastReceiver, IntentFilter). In all other ways, this behaves the same as sendBroadcast(Intent).

Example for sticky broadcast 
When you call registerReceiver() for that action -- even with a null BroadcastReceiver -- you get the Intent that was last broadcast for that action. Hence, you can use this to find the state of the battery without necessarily registering for all future state changes in the battery.

How the nine-patch Image different from a regular bitmap? or Different between nine-patch Image vs regular Bitmap Image 
It is one of a resizable bitmap resource which is being used as backgrounds or other images on the device. The NinePatch class allows drawing a bitmap in nine sections. The four corners are unscaled; the middle of the image is scaled in both axes, the four edges are scaled into one axis.

What Programming languages does Android support for application development? 
Android applications supports using Java Programming Language. which is coded in Java and complied using Android SDK.

What is a resource? 
A user defined JSON, XML, bitmap, or other file, injected into the application build process, which can later be loaded from code.
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How will you record a phone call in Android? or How to handle on Audio Stream for a call in Android? 
Permissions.PROCESS_OUTGOING_CALLS: Will Allows an application to monitor, modify, or abort outgoing calls. So through that we can monitor the Phone calls.

What's the difference between class, file and activity in android? 
Class - The Class file is complied from .java file. Android will use this .class file to produce the executable apk.
File - It is a block of resources, arbitrary information. It can be any file type.
Activity - An activity is the equivalent of a Frame/Window in GUI toolkits. It is not a file or a file type it is just a class that can be extended in Android for loading UI elements on view.

Does Android support the Bluetooth serial port profile? 
A. Yes.

Can an application be started on powerup? 
A. Yes.

What is APK format. 
The APK file is compressed AndroidManifest.xml file with extension .apk, Which have application code (.dex files), resource files, and other files which is compressed into single .apk file.

Can an application be started on powerup?

Yes.

Describe a real time scenario where android can be used?

Imagine a situation that you are in a country where no one understands the language you speak and you can not read or write. However, you have mobile phone with you.

With a mobile phone with android, the Google translator translates the data of one language into another language by using XMPP to transmit data. You can type the message in English and select the language which is understood by the citizens of the country in order to reach the message to the citizens.

What languages does Android support for application development?

Android applications are written using the Java programming language.

Frequently Asked Questions:
What is Android OS?
What is android?
What are the advantages of Android?
Explain about the exceptions of Android?
What is .apk extension?
What is .dex extension?

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