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Android Interview Questions

Q. What is Android?
It is an open-sourced operating system that is used primarily on mobile devices, such as cell phones and tablets. It is a Linux kernel-based system that’s been equipped with rich components that allows developers to create and run apps that can perform both basic and advanced functions.

Q. Who is the founder of Android?
Andy Rubin.

Q. What are the code names of android?
1.    Aestro
2.    Blender
3.    Cupcake
4.    Donut
5.    Eclair
6.    Froyo
7.    Gingerbread
8.    Honycomb
9.    Ice Cream Sandwitch
10.    Jelly Bean
11.    Kitkat
12.    Lollipop
13.    Marshmallow

Q. What are the advantages of android?
Open-source: It means no licence, distribution and development fee.
Platform-independent: It supports windows, mac and linux platforms.
Supports various technologies: It supports camera, bluetooth, wifi, speech, EDGE etc. technologies.
Highly optimized Virtual Machine: Android uses highly optimized virtual machine for mobile devices, called DVM (Dalvik Virtual Machine).

Q. Does android support other language than java?
Yes, android app can be developed in C/C++ also using android NDK (Native Development Kit). It makes the performance faster. It should be used with android SDK.

Q. What are the core building blocks of android?
The core building blocks of android are:
•    Activity
•    View
•    Intent
•    Service
•    Content Provider
•    Fragment etc.

Q. What is activity?
Activity is like a frame or window in java that represents GUI. It represents one screen of android.

Q. What are the life cycle methods of android activity?There are 7 life-cycle methods of activity.
They are as follows:
1.    onCreate()
2.    onStart()
3.    onResume()
4.    onPause()
5.    onStop()
6.    onRestart()
7.    onDestroy()

Q. What is intent?
It is a kind of message or information that is passed to the components. It is used to launch an activity, display a web page, send sms, send email etc. There are two types of intents in android:
1.    Implicit Intent
2.    Explicit Intent

Q. What is implicit intent in android?
Implicit intent is used to invoke the system components.

Q. What is explicit intent in android?
Explicit intent is used to invoke the activity class.

Q. How to call another activity in android?
1.    Intent i = newIntent(getApplicationContext(), ActivityTwo.class);
2.    startActivity(i);

Q. What is service in android?
A service is a component that runs in the background. It is used to play music, handle network transaction etc.

Q. What is the name of database used in android?
SQLite: An opensource and lightweight relational database for mobile devices.

Q. What is AAPT?
AAPT is an acronym for android asset packaging tool. It handles the packaging process.

Q. What is content provider?
Content providers are used to share information between android applications.

Q. What is fragment?
Fragment is a part of Activity. By the help of fragments, we can display multiple screens on one activity.

Q. What is ADB?
ADB stands for Android Debug Bridge. It is a command line tool that is used to communicate with the emulator instance.

Q. What is NDK?
NDK stands for Native Development Kit. By using NDK, you can develop a part of app using native language such as C/C++ to boost the performance.

Q. What is ANR?
ANR stands for Application Not Responding. It is a dialog box that appears if the application is no longer responding.

Q. What Is the Google Android SDK?
The Google Android SDK is a toolset that developers need in order to write apps on Android enabled devices. It contains a graphical interface that emulates an Android driven handheld environment, allowing them to test and debug their codes.

Q. What is the Android Architecture?
Android Architecture is made up of 4 key components:
– Linux Kernel
– Libraries
– Android Framework
– Android Applications

Q. Describe the Android Framework.
The Android Framework is an important aspect of the Android Architecture. Here you can find all the classes and methods that developers would need in order to write applications on the Android environment.

Q. What is AAPT?
AAPT is short for Android Asset Packaging Tool. This tool provides developers with the ability to deal with zip-compatible archives, which includes creating, extracting as well as viewing its contents.

Q. What is the importance of having an emulator within the Android environment?
The emulator lets developers “play” around an interface that acts as if it were an actual mobile device. They can write and test codes, and even debug. Emulators are a safe place for testing codes especially if it is in the early design phase.

Q. What is the use of an activityCreator?
An activityCreator is the first step towards the creation of a new Android project. It is made up of a shell script that will be used to create new file system structure necessary for writing codes within the Android IDE.

Q. Describe Activities.
Activities are what you refer to as the window to a user interface. Just as you create windows in order to display output or to ask for an input in the form of dialog boxes, activities play the same role, though it may not always be in the form of a user interface.

Q. What are Intents?
Intents displays notification messages to the user from within the Android enabled device. It can be used to alert the user of a particular state that occurred. Users can be made to respond to intents.

Q. Differentiate Activities from Services.
Activities can be closed, or terminated anytime the user wishes. On the other hand, services are designed to run behind the scenes, and can act independently. Most services run continuously, regardless of whether there are certain or no activities being executed.

Q. What items are important in every Android project?
These are the essential items that are present each time an Android project is created:
– AndroidManifest.xml
– build.xml
– bin/
– src/
– res/
– assets/

Q. What is the importance of XML-based layouts?
The use of XML-based layouts provides a consistent and somewhat standard means of setting GUI definition format. In common practice, layout details are placed in XML files while other items are placed in source files.

Q. What are containers?
Containers, as the name itself implies, holds objects and widgets together, depending on which specific items are needed and in what particular arrangement that is wanted. Containers may hold labels, fields, buttons, or even child containers, as examples.

Q. What is Orientation?
Orientation, which can be set using setOrientation(), dictates if the LinearLayout is represented as a row or as a column. Values are set as either HORIZONTAL or VERTICAL.


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