Android Interview Questions and Answers for Freshers
1) What is Android?
Ans: Android is an opensource Linux-based mobile operating system . which is designed to create an application for only touch screen devices. Android is not only designed to create Apps for the smartphone. which is used to create various types of applications for SmartWatches, SmartTv, Smart Cars. Android Application runs in its own process.
2) What is the main Component of Android?
Ans: The main component of android are
- Services -> Used for Performing Background Task
- Intent -> Passing Data from one Activity to another. Communicating between Activity.
- Resources ->String and Graphs
- Notification ->Used to send Notification in the form of DialogBox, AlertBox, and Toast
- Content Providers->To share the Data Between Applications.
3) What are the Features of the Android OperatingSystem?
Ans: The main features of android operating System are
- Android is an Open-source. No need for Licensing. Distribution and development is Free.
- Platform Independent which supports all Operating Systems Like Windows, Linux, Mac
- It supports various Technologies like Camera, Bluetooth, Wifi, Speech
- It uses a highly optimized virtual machine called DVM(Dalvik virtual machine).
- Supports languages Like Java, Kotlin, c++
- We can develop an App using Android Studio.
4) What is the Core building Block of Android?
Ans: The Core building Block of Android are Activity, View, Intent, Service, content providers, Fragment, Android Manifest file, AVD(Android virtual Machine)
5) What is the Role of AndroidManifest? XML File.
Ans: In the Android studio, every project should contain a Manifest file .which is stored in the root directory of the Android studio. It also defines the structure and metadata of Application. Android Manifest file contains Information About Activity, content Providers, Permission. Information About Packages, Broadcast Receiver.
6) How many ManifestFiles in Android?
Ans: We can have one or more Manifest.xml files in the Android studio.
7) What is Activity in Android?
Ans: Activity is a Single Screen of your Smartphone. It represents a Single window or Screen.
8) Which is the Parent class of Android Application?
Ans: The Application class is the Base of All Android App. Which contains Activities and services. Its instance is created before any class when the process of Application is created.
9) What is the APK file?
Ans: Apk file is compressed with UI’s, Classes Assets, and manifest file. Apk file contains Applications information like Classes and Resources, services and Layout related information.
10) Describe Android Architecture?
Ans: Android is an open-source, Linux based software created for touch screen devices. The main foundation of Android is Linux Kernel. It provides Android Run time (ART), It also provides services like Threading and Low-Level memory management.
Hardware Abstraction Layer(HAL): It provides standard interfaces that expose device hardware to a higher-level java API framework. HAL Consists of Library and Module for Camera, Bluetooth. Android System Loads Library Module for hardware component.
Android Runtime: In android, each App runs in its own process that is its own ART.ART is written to run multiple virtual machines on low memory devices by executing a DEX file.
DEX : IT is a bycode format specially designed for Android.
Native C/C++ Library : To Provide System component and Service Some of Libraries are written in c/c++.
Java API FrameWork: Android building block is JAVAAPI.
Some of the Main Features of JAVA API are:
- View System: The entire UI we are designing in Layout using grid and textbox, etc are given by view System.
- Resource Manager : It Provides Access to non-code data like strings, graphics etc.
- Notification Manager: This enables to All Apps to display custom status bar and alert.
- Activity Manager: It Controls Life Cycle of Activity.
- Content Providers: For sharing data and one App can Access data of Another App. For working with Local storage and Remote Storage we use Content Providers.
- System APP: Apart from JAVA API. A developer can also Access Some of System App Like email, SMS, Contact, Default Keybord form System App.
Q11) What is viewGroup in Android?
Ans: View Group is a special view that contain other views. View Group is Base for All Layouts. All Layouts Like Linear Layout, Relative Layout, Constrained Layout ,Table Layouts . Arranging of Layout, size, Positioning is Available in viewGroup.
Q12) What is Permission in Android?
Ans: Every App in android runs on the limited-access sandbox. If App requires information beyond in its own sandbox . then App needs permission. To declare the permission use App manifest file.To Add Permission we declare <use-permission> element in manifest file.
Q13) What is Service?
Ans: Service is a Component that runs Background. Service doesn’t have any user interface. Since Services runs Background user can continue his foreground task. Generally user doesn’t know about service. To implement a service we need to extend our class from Service Class.
Q14) Describe Activity Life Cycle.
Ans: Activity is a single screen. When user interacts with Application . then he interacts with activity. When Activity is created its Life Cycle is called. Life Cycle is managed by Activity Life Cycle Manager. There are states of Activity like
- On create() : This method is called when Activity is created. It is a Default method
- On Start() : When activity is started . it enters in OnStart() method.It makes activity visible to the user.App prepares for the activity to enter the foreground and becomes interactive to the end-user.
- OnResume() : In this state App interacts with user.The app stays until something happens to take focus away from App. For example receiving the phone calls, a user moving from one activity to another.
- OnPause():When any interruptions occurs then activity becomes paused which enters in OnPause() method.
- OnStop() : When Activity is no Longer visible to User. It enters in OnStop() method.
TO implement all these methods we need to override from CompactActivity class.
Q15) what is Bundle in Android?
Ans: a Bundle is an object . It is used to pass data between Activities. The values are passed and Mapped to String keys. Which are used to retrieve the values from Key.
Q16) What is Intent in Android?
Ans: Intent is a class used to Navigate from One Activity to Another Activity. To Navigate from one Activity to Another we use the following Syntax.
The following are the Types of Intent
- Implicit Intent : This intent will Call any web Page.
- explicit Intent : This Intent will Call Activity In same App.
Syntax of explicit Intent
Intent obj = new Intent(MainActivity.this, NextActivity.class);
startActivity(obj); // this is example of explicit Intent
Syntax of implicit Intent
Intent obj = new Intent(Intent.Action_view);
Q17) what are uses of Intent
Ans: Uses of Intent are as follows
- Intents are used for to startActivity
- Start service.
- Display webpage.
- Display List of contacts
- Broadcast the Message
- Dial a Phone Call.
Q 18) What is R.java File in Android?
Ans: R.java is an auto-generated file by Android Asset Packaging Tool. R.java contains resource id for all the resources of res/ directory. If you delete any R.java. Android will automatically create R.java.
Q19) What are Fragments in android?
Ans: Fragment is part of activity . we can even call fragment as sub Activity. Using fragment we can show multiple Activity on a single screen.
Q20) Which is the default database in Android Studio.
Ans: SQLite is the default database in Android Studio. Which is a serverless database. Which is also known as the default database in android.
Q21) what are different Dialog Boxes in Android .
Ans: Android support four types of Dialog Boxes as fallows
Alert Dialog Box: It display alert dialog messages . Which we can create using AlertDialog.Builder class
Progress Dialog Box : this Dialog Box Appears when progress completes . example when download completes .
TimePickerDialog Box: We can use this dialogBox to select Time.
DatePickerDialog: we can use this dialog box to select date.
Q22) What is SharedPreferences in Android?
Ans: In android Shared preferences are used to store and retrieve primitive information. In shared preferences, we store information in key and value formats. When we call key automatically value gets printed . The shared preferences concept is wildly used in user settings.
In order to implement the shared preference, there is a method called
Q23) what are the storage Types in android
Ans: In Android, there are two types of storage systems. Internal storage and external storage. Internal device is smaller than an external device. Internal storage is already available on every device. For external we need to extend the memory.
Q24) Describe File and Data Storage
Ans: Android uses file System similar to disk-based file System.
App-specific storage: This type of storage is only used by App. So it is App-Specific storage.
Shared Storage: this type of storage is for multimedia, files, and other documents.
Preferences: this type of storage for private primitive data in key and value pair.
Databases: In this storage, android will store a structured database using Room Persistence Library.
The limit of internal storage is limited.
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