Mostly Asked Android Jetpack Compose Interview Questions

In this blog, we will explore Mostly Asked by Interviewer Top 5 most important Android Jetpack Compose Interview Questions with Example in 2024.

Mostly Asked Top 5 Android Jetpack Compose Interview Questions with Example in 2024

Ques-1: How to launch a coroutine from a non-composable function, but tied to composition?

Ans-1: As LaunchedEffect is a composable function, it can called only inside of other composable functions. On other hand to launch a coroutine in non-composable function, but tied to scope of composition so that it will be automatically cancelled when the composable function leaves the composition, on that time we should use rememberCoroutineScope. Whenever we need to control the lifecycle of one or more coroutines task manually then we should use rememberCoroutineScope.

rememberCoroutineScope is a composable function that returns a Coroutine Scope, tied to scope of composition. This scope will be automatically cancelled when the composable function leaves the Composition.

Example:

@Composable
fun MoviesScreen(snackbarHostState: SnackbarHostState) {

// Creates a CoroutineScope bound to the MoviesScreen's lifecycle
val scope = rememberCoroutineScope()

Scaffold(
snackbarHost = {
SnackbarHost(hostState = snackbarHostState)
}
) { contentPadding ->
Column(Modifier.padding(contentPadding)) {
Button(
onClick = {
// Create a new coroutine in the event handler to show a snackbar
scope.launch {
snackbarHostState.showSnackbar("Something happened!")
}
}
) {
Text("Press me")
}
}
}
}

Ques-2: Difference between LazyColumn and RecyclerView?

Ans-2: 

LazyColumn:

• Development Experience: LazyColumn leverage in Jetpack Compose to use declarative approach using kotlin language, allowing for less line code, simpler and more concise code.
• Performance and Efficiency: LazyColumn in Jetpack Compose are create with modern rendering techniques, which also offer excellent performance with declarative approach, smooth scrolling, and efficient memory usage because less line of code needed to rendering dynamic list view and with in single function we can easily rendering dynamic list view.
• Flexibility: LazyColumn, need more streamlined, may have certain limitations or less documentation while doing customization.
• Learning Curve: LazyColumn is new in Jetpack Compose, may developers need to proper learn and familiarize themselves with the Compose framework.
• On Data Changes: LazyColumn do not need onItemChanged function because it's so efficient and its manage by own. Because when new data is added or inserted, So lazy column will only change that specific item not the whole list.

RecyclerView:

• Development Experience: RecyclerView need to writing more line of code and involves managing view holders, bind data, adapters, and layout managers.
• Performance and Efficiency: RecyclerView is known for its performance optimizations, such as view recycling its adding data only visible to screen size after scrolling again add another data and efficient scrolling.
• Flexibility: RecyclerView provides more flexibility in terms of customization of item layouts, handling different item types, its old in android development so more documentation available and easily integrating complex animations.
• Learning Curve: RecyclerView is a stable or mature component that has been widely used in Android development, making it easier to find resources/documentation and community support.
• On Data Changes: RecyclerView need onBind function for update and render all item data. So it is less efficient and expensive of changing data in recycler views because after updating of item its update whole list item.

Ques-3: Difference between mutableStateOf and remember function?

Ans-3: 

mutableStateOf: 

• mutableStateOf is that holds a value, where Compose will automatically observe changes to the value and update the UI.
• mutableStateOf function not caches value or MutableState object and always recreated or provide different instance on every recomposition.

remember:

• remember function is hold or store the state while recomposition of a composable function. Once composable function get recomposed then remember function will return previously remembered state. 
• remember function caches value or MutableState object and keep same instance on every recomposition.

For example: If we have a textView(composable function) that observes the value, first time text value is 1. Then we press the button and increment the value with 2. What happens here when the value changing from 1 to 2 the textView(composable function) recomposes itself and shows us the updated value which is 2, this is known as recomposition.

var text by remember { mutableStateOf("") } -:

- that's means we are not only observing data but also store the data across the recomposition of a composable function.

- In other words we can observe the value as well as store the value across the recomposition.

val text = remember{ "" } -:
- that's means we are only store the data across the recomposition of a composable function.

val text = mutableStateOf("")

- that's means we are only observing data and we are not store or cache of data.

Ques-4: Difference between remember and rememberSaveable function?

Ans-4: 

remember:

• remember function is used for retaining state within a composable across recompositions.
• remember is used for maintaining state that doesn't need to survive configuration changes or orientation changes.
• remember function is retained state as long as the composable is active and not destroyed until composable is destroyed.

Example:

@Composable
fun Counter() {
var count by remember { mutableStateOf(0) }
Button(
onClick = { count++ },
) {
Text(text = "Increment Counter")
}
Text(text = "Count: $count")
}
}

rememberSaveable:

• rememberSaveable function is used for preserving state across configuration changes.
• rememberSaveable is used when you want to hold or store state instance through configuration changes.
• rememberSaveable function is retained state across configuration changes or orientation changes and can outlive the composable itself.

Example: 

@Composable
fun RememberSaveableExample() {
val savedText by rememberSaveable { mutableStateOf("Initial Text") }
TextField(
value = savedText,
onValueChange = { newText ->
savedText.value = newText
}
)
Text(text = "Text Entered: $savedText")
}

Ques-5: How navigation handled in Jetpack Compose?

Ans-5: Navigation helps you in understanding how your app moves across different screens or component in your Application.

Android Jetpack Compose Navigation helps you to implementing your high-level navigation in a go easy approach.

The Navigation Component is made up of three major parts:

• Navigation Graph: This is collects all navigation-related data in one place. This handled all of the locations of your app, referred to as destinations, as well as the possible paths a user could take through your app with the help of that route user go one screen to another screen.
• NavHost: This is a unique composable that you can include in your layout. It shows various destinations from your Navigation Graph. The NavHost connected to the NavController with a navigation graph that specifies the composable function destinations that you should be able to navigate between. As you navigate between composables function, the content of the NavHost is automatically recomposed. Each destination in your navigation graph is associated with a route.
• NavController: The NavController is the central API for the Navigation component. It is stateful and keeps track of the back stack of composables function that create the screens in your app and manage the state of each screen.

Read More: Top 10 Android Jetpack Compose Interview Questions in 2024

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Conclusion 

In this blog, I have covered all Mostly Asked Top 5 Android Jetpack Compose Interview Questions in 2024. You can easily learn and prepare yourself for the interview.