Interview Questions.

Top Android Interview Questions and Answers in 2021

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Top Android Interview Questions and Answers in 2021

The Android mobile Operating System evolved via Google become to begin with launched in 2008, and noticed its cutting-edge release in August 2018, with nine.0 ‘Pie’. The Android OS is the maximum famous cellular OS in the world, with over 75% market share (Source: Stats Counter).

As the popularity of Android is soaring by means of the second, Android developers are in demand.

Top Android Interview Questions and Answers

Here we convey to you 50 pinnacle Android interview questions and solutions so that it will make you interview-equipped.

Basic Level Interview Questions

Question: Explain the build process in Android?

Answer: The build process in Android includes three steps

The first step includes the compilation of the sources folder the usage of the Android Asset Packaging Tool (AAPT). These are compiled into a single class report known as R.Java, which simplest holds constants.

In the second step, the java supply code wishes to be compiled to .Class files the usage of javac, that are then transformed to Dalvik bytecode using the ‘dx’ device, that's one of the gear inside the software development package. The very last output file is instructions.Ex.

In the 0.33 and final step, the Android apkbuilder is required to take all of the inputs and build the Android Packaging Key (APK) document.

Question: List some languages that can be used to software in Android

Answer: Below is a list of the most popular programming languages that can be used to expand applications in Android

Java: Java, the most popular programming language inside the international has usually been a starting point for new developers and used by the general public of individuals who paintings with Android improvement.

Kotlin: Kotlin is a pretty new, contemporary, safe and item-oriented cross-platform programming language. When Android studio 3.0 turned into launched in Oct 2017, Kotlin changed into announced as the legit programming language for Android. Many famous packages such as Trello, Square and Corda have given that then shifted to Kotlin.

C#: Using the C# language developers can build local iOS and Android cell applications.

Python: Python has emerged as one of the most famous programming languages in recent times. A dynamic and object-orientated programming language, Python is very famous in machine gaining knowledge of.

Other languages that may be utilized in Android are C++, HTML 5.

Question: What are the exclusive gear to be had in Android improvement? Explain their capabilities.

Answer: There are a diffusion of equipment to be had to help Android builders:

Android Software Development Kit (SDK) and Virtual Device Manager: This tool is used to generate and take care of Android Virtual Devices (AVD) and SDKs. Through the emulator in the AVD, you could specify the supported SDK version, storage within the SD card, screen decision, and other competencies such as GPS and contact screen.

The Android Emulator: The AE is the implementation of the Android Virtual Machine, designed to run processes inside a digital tool itself, which can be used on a improvement pc. The principal use of this tool is in trying out and debugging of Android applications.

Android Debug Bridge (ADB): The ADB is a command-line debugging utility doled out with the SDK. It permits developers to communicate with the tool, and facilitates actions such as the set up and debugging of an utility.

Android Asset Packaging Tool (AAPT): The AAPT builds the ‘.Apk’ distributable Android package deal document.

Question: Explain the Android Interface Definition Language.

Answer: Android Interface Definition Language or AIDL facilitates the verbal exchange among the consumer and service. For the process of conversation between methods, the information is cut up into small portions which can be without difficulty diagnosed by the Android platform.

Question: Describe Folder, File & Description of Android Applications

Answer:

gen: gen carries the compiler-generated .R record which references all the assets in the task

src: src holds the .Java source documents in our venture

bin: bin contains the .Apkk file constructed by the ADT at some point of the build manner, along with all the different matters had to run an Android utility

AndroidManifest.Xml: This report is the manifest document that explains the primary capabilities of the software and defines all its components

res/values: res/values is a directory for different numerous XML files that include assets together with strings, colour definitions and greater.

Res/drawable-hdpi: This is a listing for items that are drawable and designed for excessive-density screens

res/layout: It is a directory of files that define the UI to your utility

Question: What are ‘sports’? Describe the lifecycle of an pastime.

Answer: Activities in Android are boxes/windows to the UI. The lifecycle of an pastime is as follows

OnCreate(): Here, the perspectives are created and information is gathered from bundles.

OnStart(): It is known as if the activity is seen to the person. It may be succeeded with the aid of onResume() if the hobby reaches the foreground and onStop() if it converts into hidden.

OnResume(): It is referred to as whilst the pastime starts an interaction with the user.

OnPause(): This is referred to as while the activity goes to the heritage but hasn’t been killed but.

OnStop(): This is known as whilst you are no longer visible to the user.

OnDestroy(): Called while the interest is finishing

OnRestart(): Called after the activity has been stopped, prior to it being began once more

Question: State a few blessings of Android.

Answer: Below are some advantages of Android:

Low funding and higher returns: Android development has a low access barrier and is appropriate for brand spanking new developers looking to end up talented in the programming area.

Free SDK: One of the most prominent features of Android is that the Software Development Kit is open supply and is supplied freed from price, which eradicates the price of licensing, distribution and improvement rate.

Easy Adoption: Android packages are scripted in Java, which is one of the most used programming languages within the global.

Reusable: Android components can be reused and even replaced with the aid of the framework.

Multi-Platform Support: The Android platform helps principal OSs inclusive of Linux, Mac OS, and Windows.

Support for Wearable Devices: The market is now flooded with wearable devices and Android has emerged as main assist for such devices that are now quite simply to be had in the marketplace.

Question: What is Android Runtime?

Answer: Android Runtime (ART) is an utility utilized by the Android OS as a runtime surroundings. It has now replaced Dalvik, a discontinued technique Virtual Machine (VM). ART interprets the bytecode of the utility into native instructions, which can be completed through the tool’s runtime surroundings.

Question: Explain the conversation packing containers supported on Android.

Answer: Android supports four conversation bins

AlertDialog: The most recommended conversation container, the AlertDialog helps 0-3 buttons, in conjunction with a list of selectable gadgets, which include radio buttons and checkboxes.

DatePickerDialog: Used for the selection of date by the person

TimePickerDIalog: Used for the selection of time through the user

ProgressDialog: Used to show a development bar and is an extension of the AlertDIalog. It additionally supports the addition of buttons.

Question: What are some of the hazards of Android?

Answer: Below are a few dangers of the Android Operating System

Fake Applications: There are lots of fake apps to be had on the market at any given time, which when mounted may attempt to steal your statistics.

Streamlining problems: There are a selection of Android devices available within the market, with specific display screen sizes and dimensions, however more importantly, exceptional Android Operating Systems. Every software developer has to continuously paintings closer to updating their utility for the new OS however with diverse OS version and enhancements, the technique is quite difficult. An application which runs smoothly on one model of the Android OS might crash on a distinctive Android OS.

Background Processes: The abundance of jogging techniques within the heritage is continually an difficulty, as they devour up the battery fast.

Intermediate Level Interview Questions 

Question: Explain Sensors in Android

Answer: Android-primarily based devices have an collection of integrated-sensors in them, which measure sure parameters consisting of movement, orientation and greater. These sensors help inside the reveal of positioning and movement of the tool thru their excessive accuracy. The sensors may be both software and hardware-based on nature. The 3 prominent classes of sensors in Android devices are:

Position Sensor: It is used to degree the bodily function of the Android device. This includes orientation sensors and magnetometers.

Motion Sensors: These sensors consist of gravity, rotational interest and acceleration sensors which degree the rotation of the device or the acceleration and plenty more.

Environmental Sensor: It includes sensors that measure temperature, strain, humidity, and other environmental factors.

 

Question: Name a few checking out situations which be examined on actual gadgets and now not on emulators.

Answer: Emulators are devices which are used to perform obligations corresponding to that of real Android devices, and are used to lower the value of checking out. But some situations can simplest be executed on actual gadgets and not on emulators. These eventualities encompass:

Messaging

Bluetooth

Mounting and unmounting the memory card

Validation of battery situations

Memory related problems

Validation of the performance

Question: What is Context?

Answer: The Context in Android, as its name suggests, in the context of the contemporary country of your software or object. The context comes with services along with giving get entry to to databases and options, resolving sources and much more. There are two varieties of context:

Activity Context: This context is connected to the lifecycle of an pastime. It have to be used when you are passing the context inside the scope of an hobby or you want the context whose lifecycle is connected to the modern-day context.

Application Context: This context is hooked up to the lifecycle of an software. The software context may be used where you want a context whose lifecycle is break free the present day context or when you are passing a context beyond the scope of hobby.

Question: How do you locate reminiscence leaks in an application on the Android platform?

Answer: To discover reminiscence leaks in an application on Android, the Android Device Manager (ADM) is utilized by the Android Studio. When you open ADM in Android Studio, you may see parameters consisting of heap size and memory evaluation at the side of many others while you run an utility.

Question: State the structure of an Android utility.

Answer: Any Android application has the subsequent additives:

Notification- Features which include mild, sound, icons and greater

Services- To perform historical past functionalities

Intent- To carry out inter-connection among sports and mechanisms that skip on information

Resource Externalization- Features which include strings and pictures

Content Providers- To proportion statistics among programs

Question: If an application is crashing frequently, how are you going to troubleshoot it?

Answer: If an Android application is crashing frequently, you may do the following:

Free Memory: As there is a constrained amount of space on cell devices, you could attempt via liberating up memory area for the utility to function properly.

Compatibility Check: It won't be a hardware trouble, but greater of a software problem. It isn't always continually feasible to test an application for all gadgets and OS machine. There might be a threat that the application isn't always compatible with your OS. Check the compatibility on the application’s Google Play Store web page.

Memory Management: Some applications run perfectly on one mobile device but might also crash on other gadgets. This is where processing electricity, reminiscence control and CPU pace comes into play. Check the software memory necessities if software is constantly crashing.

App Data Usage: If an application is crashing frequently, you may delete the software’s statistics, to be able to clean its cache reminiscence and allow a few unfastened area on your device and might increase the app’s overall performance.

Question: Explain DDMS in brief.

Answer: The Dalvik Debug Monitor Server (DDMS) is a debugging tool in Android Studio. It has a extensive variety of debugging capabilities, inclusive of:

Port forwarding

Location facts spoofing

Screen capture

Logcat

Radio nation information

Thread and Heap facts

The DDMS device is now deprecated and Android now indicates the customers use Android Profiler rather.

Question: Explain the distinction among implicit and specific rationale.

Answer: Below is the distinction between the 2 intents

Explicit Intent: An explicit intent is where you inform the machine approximately which interest or machine factor it must use to generate a reaction to this motive.

Implicit Intent: An implicit rationale allows you to declare the movement you want to perform, after which the Android system will check which components are registered to address that particular action.

Question: What is the AndroidManifest.Xml document and why do you need this?

Answer: The AndroidManifest.Xml report includes facts about the application, that is then furnished to the Android machine. This facts may include the package name, components which includes pastime, offerings, content providers and greater. This record executes the following duties:

Providing a completely unique call to the Java package deal

Describing various components of the software, including pastime, offerings and more. It additionally defines the lessons to be able to put into effect these additives

Declaring the Android API so one can be used by the utility

Contains the library document info connected to the software

Question: Explain one-of-a-kind launch modes in Android

Answer: Below are the distinct launch modes in Android

Standard: This launch mode generates a brand new instance of the hobby in the task from which it originated. It is possible to create multiple times of the identical hobby, which may be delivered to the identical or exclusive tasks.

SingleTop: This release mode is similar to the Standard launch mode, besides if there exists a previous instance of the pastime on the pinnacle of the stack, then a new instance will no longer be created, however the intent can be sent to the prevailing instance of the activity.

SingleTask: This release mode will usually create a brand new task and push a brand new example to the venture as the foundation one.

SingleInstance: This release mode is the same as the SingleTask release mode but the device doesn’t release any new sports inside the same venture. In a situation wherein the brand new activity is released, it's far launched in a separate mission.

Advanced Level Interview Questions

Question: State the additives that are necessary for a New Android Project

Answer: When a new Android challenge is created, the following components are required:

Manifest: Contains the xml file

Build/: Contains build output

Res/: Contains non-code sources which includes bitmap pix, UI strings and more

Src/: Contains the code and resources

Assets/: Contains a file which can be transformed into an .Apk record

Question: What is the significance of putting in place permission in Android utility development?

Answer: If the code is on the market to anyone and without regulations, there can be a scenario where the code is compromised, resulting in defect leakage. Once the permissions are set, the code becomes to be had to legal customers most effective.

Question: Explain the term ANR in Android

Answer: The time period ANR is brief for Application Not Responding. It is displayed as a notification by the Android OS each time the utility stops responding to the user movement for a considerable amount of time.

Question: What are the one of a kind information types supported by way of AIDL?

Answer: AIDL or Android Interface Definition Language facilitates the communique among the consumer and carrier. Data Types supported with the aid of AIDL are as follows:

String

List

Map

charSequence

INT, Long, Char, Boolean (Java statistics sorts)

Question: Name the specific information storage options available on the Android platform.

Answer: Android platform gives a selection of statistics garage alternatives which can be used relying upon the want of the user. The storage options are:

SharedPreference: This option stores statistics in XML files.

SQLite: This stores structured information within the private database

Internal Storage: This shops data in the device document machine wherein it can not be examine by using other applications

External Storage: This shops information within the report gadget but it can be accessed to all apps in the device

Question: What is an Android System?

Answer: An Android System is an open-source running gadget. It is evolved to be used on smartphones and capsules. Android System is based at the Linux Kernel machine, which gives the developers to create and run applications that may perform essential in addition to advanced capabilities.

Question: Define the architecture of Android?

Answer: The Android architecture includes four additives. These are:

Linux Kernel.

Libraries.

Android applications.

Android Framework.

Android Architecture

Question: What is the overall shape of AAPT? Explain AAPT?

Answer: The complete shape of AAPT is Android Asset Packaging Tool. This device is used by builders that provide them the capability to address the zip-well matched information. Hence the method of advent, extraction, and viewing of the contents easier with this device in utility.

Question: What is an “Emulator” in Android?

Answer: An "Emulator" in android facilitates the builders to mess around an interface that acts as a real cellular device. This way, it becomes less complicated for the developers to write down and test one-of-a-kind codes for the application. The manner of debugging also turns into possible thru emulators. Hence, emulators provide a secure platform for trying out codes in their early levels as well as in the later degree while the insects need to be treated.

Question: What is an Activitycreator?

Answer: An Activitycreator is an preliminary step toward the advent of the Android challenge. It includes the shell script that may be used for growing a new file system that is important for writing codes inside the Android system.

Question: What are the sports in Android?

Answer: The activities are called a window to the person interface. It allows within the display of output or may want to even ask for inputs in order that the conversation packing containers and different roles may be finished to create a person interface.

Question: What are intents in Android system?

Answer: Intents in Android machine displays the notification messages to the customers from an Android enabled device along with smartphone, tablet, and many others. This manner, attempts are made to alert the user, and respond may be anticipated as per the intents.

Question: Is there any difference between activities and offerings?

Answer: Yes, there are numerous variations among activities and services. These variations are said as under:

Activities Services
These are closed These are open
These can be terminated at any time These cannot be terminated at any time
They are designed to run before the scenes These are designed to run behind the scenes
They are dependent They act independently
They are not continuous They are not continuous

Question: What is using XML primarily based layouts?

Answer: The XML primarily based layouts help inconsistent and preferred format for putting in place of GUI definition layout. The layout information are placed in XML files, and the alternative objects are put in supply files.

Question: Define packing containers inside the Android device?

Answer: The bins inside the Android device allows in keeping gadgets and widgets together in order that the unique items and arrangements can be fulfilled. These boxes encompass labels, buttons, fields, and so forth.

Question: Do we want Android in the mobile market?

Answer: Yes, we want Android within the mobile market as it helps the users of smartphones to download packages that may offer a ramification of offerings. The builders make diverse packages yr after yr. Android device offers them a platform from which they can display those applications to the cellphone users and discover ability clients out of them. Android device gives paid and loose packages for the customers that would comfy their facts, act as a platform for information, and offer a ramification of services as in step with the desires of the customers.

Question: Is there any drawback to the Android System? List them all.

Answer: Yes, there are numerous dangers to the Android machine. These are indexed below.

There isn't any policy on how the software may be tailored with the operating machine variations and improvements on smartphones.

Not all packages can run on each type of operating gadget of smartphones. Thus the download may want to purpose loss of information, time, and download facility.

Some of the applications in the Android gadget might not healthy the display screen of all styles of smartphones.

Android device gives such packages as nicely, which tends to acquire person statistics. This might also motive leaking of critical private data statistics from telephone customers.

Android device could provide down load software which might not be sponsored by means of credible sources and could reason damage to the cell tool.

Question: What is the total shape of ADB? Define ADB?

Answer: The complete form of ADB is Android Debug Bridge. ADB enables the developers in growing far off shell instructions. The fundamental characteristic of ADB is to permit and manipulate the verbal exchange procedure towards emulator port and later getting a reaction from it.

Question: What are the states in an interest?

Answer: There are 4 states in an interest. These encompass the following.

Active country: In this state, the pastime is inside the foreground.

Paused kingdom: In this state, the pastime is in the history and seen.

Stopped country: on this nation, the interest is at the heritage but no visible or even hidden or obscure other activities.

Destroyed country: In this state, the interest is absolutely terminated or killed or eliminated.

Question: What is the entire form of ANR? Define ANR?

Answer: The full form of ANR is Application Not Responding. ANR is a talk that appears on the display screen of the utility person on its electronic tool. It appears while the software is unresponsive for a extra extended duration.

Question: What are the permissions in the utility improvement system?

Answer: The permissions in the utility improvement technique consist of regulations that are imposed to shield the information and code. These permissions are implemented to guard the utility from getting compromised, attacked by means of viruses, steal away users' records, and to purpose malicious program defects.

Question: What are the intent filters?

Answer: The cause filters are the essential additives of the Android system as it enables in responding, filtering, and receiving the right facts inputs.

Question: Are there any important loops while tracking an interest?

Answer: Yes, three key loops tracking an hobby. These consist of the subsequent.

Loop 1: Entire Lifetime: In this key loop, the hobby takes place among the onCreate and onDestroy.

Loop 2: Visible Lifetime: In this key loop, the hobby happens between onStart and onStop.

Loop 3: Foreground Lifetime: In this key loop, the activity happens between onResume and onPause.

Question: What are the possible states in which a system is based totally?

Answer: The feasible states in which a manner is based totally encompass the subsequent.

State 1: Foreground hobby

State 2: Visible pastime

State 3: Background hobby

State 4: Empty pastime

Question: Can we save you ANR in the Android system?

Answer: Yes, we can save you ANR inside the Android device. ANR hinders the Android gadget from concluding a code that has been responsive for a long term. The prevention may be made with the aid of developing a toddler thread in which most of the real workings of the codes can be carried out, and the minimal duration unresponsive times can be found out.

Question: What is Dalvik? How is it useful to Android System?

Answer: Dalvik is a digital system that helps the Android machine is walking its packages. It enables the smartphones and other electronic devices to download the programs from the digital machines which have every software saved in its memory. The new packages, their elimination, and updates are all made inside the Dalvik platform.

Question: What are the Default Resources? How are they beneficial?

Answer: The Default assets encompass the default strings and documents. Their absence will result in growing mistakes on the screen and can also prevent the going for walks of the downloaded software. They are beneficial as they may be positioned as subdirectories under the undertaking directory, which helps the jogging of the downloaded software.

Question: Define AIDL?

Answer: AIDL stands for Android Interface Definition Language. AIDL is used for coping with the interface requirements that exist between the purchaser and the carrier issuer. It acts as a platform to speak at the equal stage via the interprocess communication or IPC technique. The steps accompanied in AIDL includes breaking down the targets into primitives so that the Android device can recognize them nicely. AIDL also allows in proscribing the applications from fetching information from other devices.

Question: What is a Fragment in the Android gadget?

Answer: A Fragment within the Android system is a part of the interest, that's modular in a experience. They can move round and could even combine with different fragments to form a unmarried interest. Fragments are reusable.

Conclusion

So this became a list of the 50 Top Android interview questions and answers. Do you've got every other questions that we left unanswered? Let us recognise thru the comments below. Also, don’t forget to check our exceptional Android tutorials encouraged via the network.

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