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• Roadmap 2024 - Topics
• Roadmap 2024 - Week Schedule

• Kotlin
• Android
• Lifecycle
• Networking
• Webview
• Dependency Injection
• Jetpack Compose
• Thread
• Architecture
• Design Pattern
• System Design
• Libraries
• Common Question
• Questions from Company
• Kotlin Sheet 2024
• Jetpack Compose Sheet 2024

• What is the difference betweenconst val andval?
  • Both are used to define read-only properties, but
  • const val properties should be initialized at compile-time whereasval properties can be initialized at runtime
  • If we decompile,const val variable will replace with its value butval not, because it can be initialized at runtime

  • const val BASE_URL = "https://github.com"val githubHandle = "anandwana001"val repoName: String

• What is so interesting aboutdata class?
  • Uses to hold data
  • Pre-functions liketoString,equals,copy, andcomponentN
  • Data classes cannot be abstract, open, sealed, or inner.
  • Data classes cannot extend other classes
  • Supports destructuring declaration
• Is singleton thread-safe? vs Object?
• What are the different types of scope functions?
  • Let =T.let { R }
    • lambda result (R) is the return type
    • can be performed on anyT type object
    • lambda reference isit
    • suitable for null check
  • Run =T.run { R }
    • same aslet, but mostly used in initializing an object
    • lambda reference isthis
    • suitable for null check
  • With =with(T) { R }
    • if T is nullable object userun else usewith(T)
    • lambda reference isthis
    • not suitable for null check
  • Also =T.also { T }
    • when need to perform multiple operations in chain usealso
    • lambda reference isit
  • Apply =T.apply { T }
    • when need to perform the operation on theT object and return the same useapply
    • lambda reference isthis
    • suitable for null check
• What are the different Coroutine Scopes?
• How to manage series and parallel execution?
• Difference between Flow/SharedFlow/StateFlow and elaborate it.
• What happens if we call.cancel() from a coroutine scope?
• What is an Init block in Kotlin?
• How to choose between apply and with?
• What is inline function in Kotlin?
• Difference between Coroutine and Java Thread
• Why Coroutines are light weight?
• How does Coroutine switch context?
• When to use Kotlin sealed classes?
• Suspending vs Blocking in Kotlin Coroutines
• What are Dispatchers and Name all of them
• On which thread Dispatchers .Default execute the task or use which thread?
• Dispatchers .Default vs Dispatcher .IO
• What is SupervisorScope?
• Exception Handling in Coroutine
• Map vs FlatMap in kotlin
• Singleton Pattern in Kotlin with object keyword
• Collections API in Kotlin
• What is Unidirectional Flow
• StateFlow vs SharedFlow
• Builder Pattern in Kotlin
• Higher Order Functions in Kotlin
• Covariance in Kotlin
• Delay vs Thread.sleep?Answer

• How does Garbage collection works?
• What is a dangling pointer?
• Elaborate Memory Leak?
• Explain fragment Lifecycle when it comes to ViewPager and sliding between different fragments.
• Difference between FragmentStateAdapter and FragmentStatePagerAdapter.
• Difference between Serializable and Parcelable? What are the disadvantages of Serializable?
• How you could implement observable SharedPrefs or observable Databases i.e. Observe a certain key/table/query?
• How does layout inflation work from xml tags to view references in memory?
• What is a Thread, Handler, Looper, and Message Queue?
• What are the different methods of concurrency on Android? Can you explain the difference between ExecutorService vs CachedThreadPool vs FixedThreadPool vs AsyncTasks vs HandlerThreads?
• How doesViewModel instance provide to Activity and Fragment? How doesViewModelProviderStore decide when to retain the instance?
• How do you inspect and solve the Jank issue?here
• How does the OutOfMemory happen?
• How do you find memory leaks in Android applications?
• What is Doze? What about App Standby?
• What doessetContentView do?
• Process of creating a custom view
• Deeplink understanding and architecture
• Notifications
• Difference between Fragment Lifecycle Observer and View Lifecycle Observer.
• When should you use a Fragment rather than an Activity?
• Explain the Android push notification system.
• How LiveData is different from ObservableField?
• What is the difference between setValue and postValue in LiveData?
• What is process death?
• What is ViewModelScope and How does it work internally?

• How to keep a video maintain a playing state when we rotate the screen?
• How many callbacks are in Fragments?
• What could be the reasons whyonPause didn't get triggered?
• What kind of events triggeronPause() to run?
• In what scenario does the "onDestory" get called directly after "onCreate"?
• Which callback gets called on Activity when an AlertDialog is shown?
• What's the lifecycle in PIP (Picture-in-Picture)?
• What happens if you rotate the device?
• Inside a viewpager (Fragment state pager adapter) what will be the lifecycle of the fragments when you swap from one tab to another?
• Why onActivityCreated is now depreciated in Fragment?
• Which callback should I use if I want to know when my activity came to the foreground?
• When is onActivityResult called?
• What does setRetainInstance do and how you can avoid it?
• What callbacks trigger when a Dialog opens up? In both cases, the dialog is attached from the same activity/fragment and another activity/fragment.
• What dolaunchWhenCreated,launchWhenStarted, andlaunchWhenResumed functions do?
• Fragment Callbacks when moving from one fragment to another and coming back to prev one?
• Does onCreateView get called after coming to a fragment from top fragment?
• When does ViewModel not survive

Code

supportFragmentManager.beginTransaction()    .replace(R.id.fragment_container, FragmentA())    .commit()

Callbacks

Code

parentFragmentManager.beginTransaction()    .add(R.id.fragment_container, FragmentB())    .commit()

parentFragmentManager.beginTransaction()    .add(R.id.fragment_container, FragmentB())    .addToBackStack(null)    .commit()

Callbacks

Code

parentFragmentManager.beginTransaction()    .replace(R.id.fragment_container, FragmentB())    .addToBackStack(null)    .commit()

Callbacks

Code

parentFragmentManager.beginTransaction()    .replace(R.id.fragment_container, FragmentB())    .commit()

Callbacks

Note: IfaddToBackStack is not used, and back stack is empty, nothing will happen when callingpopBackStack() function

Code

// FragmentAparentFragmentManager.beginTransaction()    .add(R.id.fragment_container, FragmentB())    .addToBackStack(null)    .commit()// FragmentBparentFragmentManager.popBackStack()

Callbacks

FragmentA is visible. No FragmentA callbacks as FragmentA is always there, neither the view nor the lifecycle get affected.

Note: IfaddToBackStack is not used, and back stack is empty, nothing will happen when callingpopBackStack() function

Code

// FragmentAparentFragmentManager.beginTransaction()    .replace(R.id.fragment_container, FragmentB())    .addToBackStack(null)    .commit()// FragmentBparentFragmentManager.popBackStack()

Callbacks

FragmentA view is created again. When replacing, the FragmentA view gets destroyed,onDestroyView gets called so when coming back it callsonCreateView to initialise the view again.Though,onCreate will not get called again.

There are 5 States:

• DESTROYED
• INITIALIZED
• CREATED
• STARTED
• RESUMED

States are based on Context/Scope you are using in.Example:

viewLifecycleOwner.lifecycleScope.launch {    repeatOnLifecycle(Lifecycle.State.CREATED) {        //...    }}// viewLifecycleOwner => Lifecycle of the View// should be used between onCreateView() and onDestroyView()

this.lifecycleScope.launch {    repeatOnLifecycle(Lifecycle.State.CREATED) {        //...    }}// this => Lifecycle of Fragment or Activity

• if state CREATED and app moves to background, it will listen. Hence, Avoid UI work here
• use state CREATED if need to complete action even after Fragment View destroy

• What is the role of OkHttp and Retrofit?
• What design pattern does Retrofit use?
• How would optimize the handling of access token expiration? How would you handle a retry network call when the API fails? (Custom Interceptor response)

• What are the problems around security when dealing withWebView?
• How to interact or make connections with JavaScript?

• Provides vs binds
• Subcomponent vs. component dependency, what is the difference under the hood
• What is a subcomponent and what is its use? How do you use qualifiers or how would you provide different instances of a class with the same data type? Constructor Injection V/s Method Injection? What is the scope? Singleton Annotation?
• What is Circular dependency in dagger? and how to resolve it
• What's interesting about Hilt?
• Did you use Koin? What are your thoughts on it?

• How to launch a coroutine from a composable function? -LaunchedEffect
• How to launch a coroutine from a non-composable function, but tied to composition? -rememberCoroutineScope()
• What is recomposition?Recomposition
• What isremember in compose?
  • A composable function to remember the value produced by a calculation only at the time of composition. It will not calculate again in recomposition.
  • Recomposition will always return the value produced by composition.
  • Whole Compose is based on the concept ofPositional Memoization
  • At the time of recomposition,remember internally calls a function calledrememberedValue() whose work is to look into theslotTable and compare if the previous value and the new value have any difference, if not return, else update the value
• Why and when to useremember {}?
• Difference betweenLazyColumn andRecyclerView?
• What is AndroidView in compose?
• What is the lifecycle of composeables?Lifecycle
• How to avoid recomposition of any composable, if the state is not changed?Smart Recomposition
• What are stable types that can skip recomposition?
• What is State?
• What is MutableState and how does recomposition happen?
• How to retain State across recomposition and configuration changes?
• Difference between Stateless and Stateful composeables?
• What are your thoughts on flat hierarchy, constraint Layout in compose vs. the older view hierarchy in xml
• Difference b/w remember and LaunchedEffect
• Does re-composition ofComposeItem1 bring any effect onComposeItem2? If yes, then how?
  • ComposeParent() { ComposeItem1 {} ComposeItem2() {...} }
  • What isCompositionLocal?
• Custom views in compose
• Canvas in Compose
• What are the benefits of Jetpack Compose?
• How does Jetpack Compose integrate with existing Android frameworks and libraries?
• What are the best practices for performance optimization in Jetpack Compose?
• How is navigation handled in Jetpack Compose?
• What is Strong Skipping Mode?Answer

• Different types of threads?
• Difference between different types of thread?
• Thread <-> Handler <-> looper
• UI vs Background Thread
• How do you know when some process if blocking a UI thread?

• What are SOLID principles?
• What is MVVM?
• Brief about Android Architecture.
• MVP vs MVVM?
• Is there any issue in the Presenter in the MVP?
• Clean Architecture
• MVVM vs MVI
• What is Clean Architecture in MVVM
• What are Provides and Binds in your Dagger library

• What is SOLID principle?
• What are different design patterns you know about?
• What is a creational pattern?
• What is a structural pattern?
• What is a behavioral pattern?
• Create Singleton Pattern without Kotlin default implementation
• Create Observer Pattern
• Create Adapter Pattern
• How to make a Singleton Pattern Thread Safe?
• What is Dependency Inversion
• Write a real-life example of Dependency Injection without using any library
• Explain how Android Architecture components (ViewModel, LiveData, etc.) utilize design patterns behind the scenes

• Design Image Loading Library
• Design Image Downloading Library
• Design LRU Cache
• Design a real-time Twitter feed timeline. How will you structure the backend? Will you use WebSocket or REST for this use case? Justify.
• Design Networking Library
• Design Checkout Screen
• Design Error handling Structure
• REST <-> Web Sockets
• Implement caching mechanism
• Build an offline-first app
• Design Analytics Library

• How does Glide internally work?
• How does retrofit work internally?
• ViewModel internal working
• How will you choose between Dagger 2 and Dagger-Hilt?

• String vsStringBuilder
• == vs.equals?
• === vs==?
• Java OOP concepts

Topics	Sub-Topics
Programming Languages	Kotlin Java
Android Architecture
Runtime	Dalvik Virtual Machine Android Runtime
Android Manifest	Package Application Id
Permissions	Install-time Permissions Special Permissions Runtime Permissions Permissions Groups
Android Build	APK AAB
Thread	Processes Threads Inter Process Communication Handlers Loopers Message Queue UI Thread Background Thread Heap & Stack
Fundamental Components	Activity Services Broadcast Receiver Content Provider
Intent	Implicit Intent Explicit Intent Intent Filters Intent Flags
Activity	Activity Lifecycle Tasks and Back Stacks Bundles Parcelables Recent Screens App Shortcuts Context
Services	Service Lifecycle Foreground Service Background Service Bound Service AIDL Job Scheduler WorkManager IntentService
Broadcast Receiver	Pub-Sub System Broadcast Permissions Security
Content Provider	Content Resolver Cursor MIME Types Contracts
Data Storage	App Specific Storage Shared Storage Preferences Database Scoped Storage LRU Cache SQLite ROOM Data Store
Fragments	Fragment Lifecycle Dialog Fragment Fragment Transactions Fragment Manager View Lifecycle BackStack Fragment-Activity Communication Fragment-Fragment Communication
Navigation Component	Host Graph Controller Back Stacks Destinations Deeplink
Jetpack Components	ViewModel LiveData Paging Lifecycle WorkManager Data Binding
UI	XML Jetpack Compose
Jetpack Compose	Composition ReComposition State Hoisting Remember RememberSaveable Side Effects LaunchedEffect DisposableEffect DerivedStateOf SnapshotFlow CompositionLocal Theming Modifier Layouts Box/Column/Row Image/painter Coil LazyColumn/LayRow Text/Button/ other ui components
Testing	UI Testing Unit Testing Espresso Robolectric Mockk
Debugging	Logcat Timber Break Points Chucker Charles LeakCanary
Libraries	Retrofit OkHttp Glide Material3 Hilt Dagger Retrofit
Benchmark	Micro Benchmark Macro Benchmark
Static Analysis	Ktlint Detekt Android Lint
GitHub Actions	Pipeline Build Generation Workflow
Gradle	Commands Groovy
Common Errors	ANR App Crash Fatal Error OOM ArrayOutOfBound
Proguard	Obfuscation Keep
Code Architecture	MVP MVVM MVI Modularization Design Patterns Network Layer Data Layer UI Layer Domain/Repository/...
Firebase	Crashlytics Remote Config A/B Testing
App Release	App Release Process App Distribution Google Play Console App Review/Ratings App Size App Policies

What interesting questions do you face while giving an interview for an Android Engineer role (any level)? Let's open a PR.