Android-Interview-Questions

Collaboration Rules

Make sure your question is new and unique - not just rephrasing a previously existing question. If possible, include a link to the solution/topic. Questions should be fairly straightforward and completely technical (no "how many golf balls are in America" questions.) If there is a new topic that you think should be included, then include it!

Topics:

• General Developer Questions
• Core Java
• Core Android
• Android Design and XML
• Android Networking
• Databases

General Developer Questions

• How familiar you are with the Android and Google Guidelines?
• Describe Test-Driven Development. [info]
• Explain unit tests versus functional tests.
• Describe Scrum and Kanban.
• What project management tools have you used?
• How do you ensure that you are working efficiently?
• Do you have basic familiarity with working on the command line i.e. Gradle, Ant, or the Java Compiler?

Core Java

Object-Oriented Programming

• What are the main 3 Object Oriented Programing (OOP) concepts?
• Explain object serialization and how to implement it in Java.
• Explain anonymous classes. [info]
• Describe the differences between abstract classes and interfaces. [info]
• Explain what a Singleton class is and how to create one in Java [info]
• Why should the equals() and hashCode() methods often be overridden together? [info]
• How do you properly override the equals() method? For example, what considerations should be taken when checking for equality? [info]
• Difference between final, finally and finalize?
• In Java, does the finally block gets executed if we insert a return statement inside the try block of a try-catch-finally? [info]
• Explain method overloading & overriding.
• What is memory leak and how does Java handle it? [info]

Data Structures

• What are the use cases and differences of arrays and ArrayLists?
• What are the use cases and differences of a HashSet and a TreeSet? [info]

Build Tools

• Have you used any Ant, Maven, Gradle features for your project?

Programming Paradigms

• Explain event-driven programming in Java [info]
• What is Java's Garbage Collection and how does it help you as a developer?
• How can you typecast in Java? [info]
• Explain Java's try-catch-finally paradigm [info]

Core Android

• How does the Android notification system work?
• How can two distinct Android apps interact? (several answers)
• Describe Activities. [info]
• What are the four states of the Activity Lifecycle? [active/running, paused, stopped, destroyed]
• What are the seven callback methods of an Activity used to perform operations when the Activity transitions between states? [onCreate(), onStart(), onResume(), onPause(), onStop(), onRestart(), onDestroy()]
• What is the difference between a fragment and an activity? Explain the relationship between the two. [info]
• What is the difference between Serializable and Parcelable? Which is the best approach in Android? [info]
• What are "launch modes"? [info]
• What are Intents? [info]
• What is an Implicit Intent? [info]
• What is an Explicit Intent? [info]
• Describe three common use cases for using an Intent.
• What is a Service? [info]
• What is a ContentProvider and what is it typically used for? [info]
• What is a Fragment? [info]
• What is ADB?
• What is ANR?
• What is AndroidManifest.xml used for? Give examples of what kind of data you would add to it. [info]
• Describe how broadcasts and intents work to be able to pass messages around your app.[info]
• What is the Dalvik Virtual Machine?
• What are different ways to store data in your Android app? [info]
• Android appplication components [info]
• What is the relationship between the life cycle of an AsyncTask and an Activity? What problems can this result in? How can these problems be avoided?
• What is the difference between Service and IntentService? How is each used? [info]
• What is a Sticky Intent? [info]
• What is AIDL? [info]
• What is dependency injection?
• What are the different protection levels in permission? [info]
• How would you preserve Activity state during a screen rotation?

Android Design and XML

• Explain the differences and similarities of Relative Layout and Linear Layout.
• Explain the differences and similarities of List Views and Grid Views.
• Describe how to implement XML namespaces.
• Explain how to present different styles/drawables for a button depending on the state of the button (pressed, selected, etc.) using XML (no Java) [info]
• for layout_width and layout_height, what's the difference between match_parent and wrap_content?
• How do you implement Google's new Material Design in an Android application? [info]
• Difference between View.GONE and View.INVISIBLE? [info]

Android Networking

• Have you use an HTTP Library, which, why, did you like it?
• Describe how REST APIs work.
• What are some typical methods of HTTP request/responses? [GET, POST, PUT, PATCH, DELETE, UPDATE]

Databases

• Why does Android use SQLite?
• What libraries have you used for interacting with databases and why did you choose them?
• What are contract classes? [info]
• How do you use the BaseColumns interface to describe your data schema? [info]