Android Interview Questions and Answers
Q1. What is Android?
Ans: It is an open-sourced operating machine that is used by and large on cell devices, which include cell phones and pills. It is a Linux kernel-based totally machine that’s been ready with wealthy additives that lets in builders to create and run apps which can carry out both simple and superior functions.
Q2. What Is the Google Android SDK?
Ans: The Google Android SDK is a toolset that builders want with a view to write apps on Android enabled gadgets. It carries a graphical interface that emulates an Android driven hand-held surroundings, allowing them to test and debug their codes.
Q3. What is the Android Architecture?
Ans: Android Architecture is made of four key additives:
Q4. Describe the Android Framework.
Ans: The Android Framework is an essential thing of the Android Architecture. Here you can locate all of the lessons and techniques that builders would want which will write packages at the Android surroundings.
Q5. What is AAPT?
Ans: AAPT is short for Android Asset Packaging Tool. This tool affords builders with the ability to address zip-compatible records, which includes growing, extracting in addition to viewing its contents.
Q6. What is the significance of getting an emulator inside the Android surroundings?
Ans: The emulator lets builders “play” round an interface that acts as though it have been an real cellular device. They can write and test codes, and even debug. Emulators are a secure region for testing codes specifically if it is inside the early design segment.
Q7. What is the use of an activityCreator?
Ans: An activityCreator is the first step closer to the creation of a new Android project. It is made up of a shell script that will be used to create new record system shape important for writing codes within the Android IDE.
Q8. Describe Activities.
Ans: Activities are what you seek advice from because the window to a person interface. Just as you create windows with the intention to show output or to ask for an input in the form of dialog containers, sports play the same role, though it may no longer constantly be in the shape of a consumer interface.
Q9. What are Intents?
Ans: Intents displays notification messages to the user from inside the Android enabled device. It can be used to alert the person of a particular kingdom that came about. Users may be made to respond to intents.
Q10. Differentiate Activities from Services.
Ans: Activities may be closed, or terminated every time the person wishes. On the opposite hand, offerings are designed to run behind the curtain, and might act independently. Most services run constantly, no matter whether there are positive or no activities being performed.
Q11. What gadgets are vital in every Android venture?
Ans: These are the important objects which can be gift every time an Android challenge is created:
Q12. What is the significance of XML-based layouts?
Ans: The use of XML-based totally layouts presents a regular and extremely trendy method of setting GUI definition format. In common practice, format details are positioned in XML files at the same time as other items are positioned in source documents.
Q13. What are bins?
Ans: Containers, because the name itself implies, holds objects and widgets together, relying on which precise objects are needed and in what precise arrangement that is wanted. Containers may keep labels, fields, buttons, or even toddler packing containers, as examples.
Q14. What is Orientation?
Ans: Orientation, which can be set the use of setOrientation(), dictates if the LinearLayout is represented as a row or as a column. Values are set as both HORIZONTAL or VERTICAL.
Q15. What is the importance of Android within the cell marketplace?
Ans: Developers can write and sign in apps with a view to particularly run under the Android surroundings. This manner that every cellular device that is Android enabled can be able to assist and run these apps. With the developing popularity of Android cell devices, developers can take gain of this fashion via developing and uploading their apps at the Android Market for distribution to everybody who desires to down load it.
Q16. What do you think are a few risks of Android?
Ans: Given that Android is an open-source platform, and the truth that distinct Android running structures had been launched on exceptional cellular gadgets, there’s no clear reduce policy to how programs can adapt with numerous OS versions and enhancements. One app that runs on this particular model of Android OS may additionally or may not run on every other version. Another downside is that given that mobile gadgets together with phones and tabs come in distinct sizes and forms, it poses a mission for builders to create apps that can modify correctly to the proper display screen length and other varying capabilities and specifications.
Q17. What is adb?
Ans: Adb is brief for Android Debug Bridge. It permits builders the strength to execute faraway shell commands. Its primary function is to allow and manage communication toward and from the emulator port.
Q18. What are the four crucial states of an pastime?
Active – if the hobby is at the foreground
Paused – if the hobby is at the background and still seen
Stopped – if the interest is not seen and therefore is hidden or obscured by means of some other activity
Destroyed – whilst the hobby manner is killed or finished terminated
Q19. What is ANR?
Ans: ANR is short for Application Not Responding. This is certainly a dialog that looks to the person each time an software have been unresponsive for a long time period.
Q20. Which factors can arise best once and have to be gift?
Ans: Among the distinctive factors, the and factors need to be present and might occur handiest once. The rest are optionally available, and may arise as often as needed.
Q21. How are escape characters used as attribute?
Ans: Escape characters are preceded with the aid of double backslashes. For example, a newline person is created the usage of ‘n’
Q22. What is the significance of settings permissions in app development?
Ans: Permissions permit positive regulations to be imposed more often than not to protect statistics and code. Without those, codes will be compromised, ensuing to defects in capability.
Q23. What is the feature of an rationale filter out?
Ans: Because every component needs to indicate which intents they are able to reply to, purpose filters are used to filter intents that those components are willing to receive. One or extra motive filters are viable, relying on the services and sports this is going to utilize it.
Q24. Enumerate the 3 key loops whilst tracking an activity
Entire lifetime – hobby happens among onCreate and onDestroy
Visible lifetime – interest happens among onStart and onStop
Foreground lifetime – hobby takes place between onResume and onPause
Q25. When is the onStop() method invoked?
Ans: A name to onStop technique happens when an hobby is now not visible to the consumer, either due to the fact every other interest has taken over or if in the front of that pastime.
Q26. Is there a case wherein different qualifiers in more than one assets take priority over locale?
Ans: Yes, there are absolutely times in which a few qualifiers can take precedence over locale. There are acknowledged exceptions, which are the MCC (mobile u . S . Code) and MNC (mobile community code) qualifiers.
Q27. What are the distinct states wherein a procedure is based totally?
Ans: There are 4 feasible states:
historical past interest
Q28. How can the ANR be averted?
Ans: One method that stops the Android device from concluding a code that has been responsive for a protracted time period is to create a child thread. Within the child thread, maximum of the actual workings of the codes may be placed, in order that the principle thread runs with minimum durations of unresponsive times.
Q29. What function does Dalvik play in Android improvement?
Ans: alvik serves as a virtual device, and it's miles where every Android application runs. Through Dalvik, a tool is capable of execute a couple of digital machines successfully thru better memory management.
Q30. What is the AndroidManifest.Xml?
Ans: This record is critical in every application. It is asserted in the root listing and incorporates information about the software that the Android device need to realize before the codes can be done.
Q31. What is the right way of setting up an Android-powered tool for app development?
Ans: The following are steps to be observed previous to real utility improvement in an Android-powered tool:
-Declare your software as “debuggable” in your Android Manifest.
-Turn on “USB Debugging” for your device.
-Set up your gadget to come across your tool.
Q32. Enumerate the stairs in developing a bounded provider thru AIDL.
create the .Aidl file, which defines the programming interface
2. Implement the interface, which includes extending the internal abstract Stub elegance as well as implanting its methods.
Three. Expose the interface, which entails imposing the carrier to the clients.
Q33. What is the significance of Default Resources?
Ans: When default assets, which comprise default strings and documents, aren't gift, an errors will arise and the app will not run. Resources are positioned in in particular named subdirectories under the challenge res/ directory.
Q34. When dealing with a couple of sources, which one takes precedence?
Ans: Assuming that every one of those a couple of sources are capable of in shape the configuration of a tool, the ‘locale’ qualifier nearly always takes the very best priority over the others.
Q35. When does ANR arise?
Ans: The ANR dialog is exhibited to the user based totally on possible conditions. One is when there is no reaction to an enter occasion inside 5 seconds, and the alternative is whilst a published receiver isn't finished executing inside 10 seconds.
Q36. What is AIDL?
Ans: AIDL, or Android Interface Definition Language, handles the interface necessities among a purchaser and a carrier so both can talk on the identical degree via interprocess communication or IPC. This technique involves breaking down gadgets into primitives that Android can understand. This component is needed actually due to the fact a procedure can not get entry to the reminiscence of the opposite technique.
Q37. What records kinds are supported via AIDL?
Ans: AIDL has guide for the subsequent facts sorts:
all native Java data types like int,long, char and Boolean
Q38. What is a Fragment?
Ans: A fragment is part or part of an interest. It is modular in a sense that you could flow round or integrate with other fragments in a unmarried hobby. Fragments also are reusable.
Q39. What is a seen activity?
Ans: A seen interest is one that sits in the back of a foreground dialog. It is actually seen to the user, but no longer necessarily being in the foreground itself.
Q40. When is the nice time to kill a foreground pastime?
Ans: The foreground interest, being the most crucial some of the other states, is most effective killed or terminated as a last motel, particularly if it's miles already ingesting an excessive amount of memory. When a memory paging kingdom has been reach with the aid of a foreground interest, then it is killed in order that the person interface can hold its responsiveness to the user.
Q41. Is it possible to use or add a fragment without the usage of a person interface?
Ans: Yes, it's far possible to try this, including when you need to create a historical past conduct for a selected hobby. You can try this by way of the usage of add(Fragment,string) approach to feature a fraction from the interest.
Q42. How do you dispose of icons and widgets from the principle display screen of the Android device?
Ans: To eliminate an icon or shortcut, press and keep that icon. You then drag it downwards to the lower a part of the display screen wherein a do away with button seems.
Q43. What are the middle components beneath the Android software structure?
Ans: There are five key additives underneath the Android application architecture:
content material providers
Q44. What composes a standard Android software assignment?
Ans: A assignment below Android development, upon compilation, will become an .Apk file. This apk report layout is truly made of the AndroidManifest.Xml report, application code, useful resource files, and different related documents.
Q45. What is a Sticky Intent?
Ans: A Sticky Intent is a printed from sendStickyBroadcast() method such that the motive floats around even after the printed, permitting others to collect information from it.
Q46. Do all mobile telephones help the ultra-modern Android running device?
Ans: Some Android-powered smartphone permits you to improve to the better Android running device version. However, now not all improvements might assist you to get the modern-day version. It relies upon largely at the capability and specifications of the cellphone, whether or not it may support the more moderen functions to be had beneath the state-of-the-art Android model.
Q47. What is portable wireless hotspot?
Ans: Portable Wi-Fi Hotspot permits you to percentage your cellular net connection to other wireless device. For instance, the use of your Android-powered phone as a Wi-Fi Hotspot, you can use your laptop to hook up with the Internet the use of that get admission to point.
Q48. What is an action?
Ans: In Android development, an action is what the rationale sender wants to do or expected to get as a response. Most application functionality is primarily based on the meant movement.
Q49. What is the distinction among a everyday bitmap and a 9-patch photograph?
Ans: In widespread, a Nine-patch image lets in resizing that can be used as background or different photograph length requirements for the target device. The Nine-patch refers back to the way you can resize the photo: four corners that are unscaled, four edges which are scaled in 1 axis, and the middle one that may be scaled into each axes.
Q50. What language is supported by way of Android for application development?
Ans: The important language supported is Java programming language. Java is the most famous language for app improvement, which makes it best even for brand new Android builders to quick discover ways to create and deploy programs in the Android surroundings.