FIT5046 - Week 3: Jetpack Compose State, ViewModels, and Lazy Lists Flashcards

Question 1

What is the core idea of a declarative UI framework like Jetpack Compose?

Accepted Answer

You describe what the UI should look like, and Compose updates it automatically when the state changes.

Question 2

How does updating a UI widget in Compose differ from using an imperative setter method?

Accepted Answer

In Compose, you call the composable function again with new data, which is known as recomposition.

Question 3

What is recomposition in Jetpack Compose?

Accepted Answer

The process of redrawing and regenerating the affected parts of the screen when UI state changes.

Question 4

Why is recomposition in Jetpack Compose highly efficient?

Accepted Answer

It only updates the specific parts of the UI tree that depend on the changed state, rather than redrawing the entire screen.

Question 5

Does Jetpack Compose automatically observe changes to standard Kotlin variables?

Accepted Answer

No, you must explicitly declare which data to track using state holders.

Question 6

What is MutableState in Jetpack Compose?

Accepted Answer

An observable state holder type that allows Compose to observe changes and trigger recomposition.

Question 7

What is the purpose of the remember{} function in Jetpack Compose?

Accepted Answer

It is used to retain and protect state values across recompositions.

Question 8

How do you declare a MutableState using the value property (Option 1)?

Accepted Answer

val stateName = remember { mutableStateOf(defaultValue) }

Question 9

When using val name = remember { mutableStateOf() }, how must you access or modify its actual string value?

Accepted Answer

By using the .value property (e.g., name.value).

Question 10

How do you declare a MutableState using property delegation (Option 2)?

Accepted Answer

var stateName by remember { mutableStateOf(defaultValue) }

Question 11

When using var name by remember { mutableStateOf() }, why is the .value property not needed?

Accepted Answer

The by keyword acts as a delegate, passing the getter and setter responsibility directly to the MutableState object.

Question 12

Which two imports are required when using the property delegate by keyword in Compose?

Accepted Answer

getValue and setValue from androidx.compose.runtime.

Question 13

What is a major limitation of using remember{} to hold state?

Accepted Answer

It retains state across recompositions but not across configuration changes like screen rotation.

Question 14

Which function is used to retain UI state across activity destruction and recreation (such as screen rotation)?

Accepted Answer

rememberSaveable

Question 15

What is a key difference in applicability between rememberSaveable and ViewModels?

Accepted Answer

rememberSaveable only works within Compose, while ViewModels work both with and without Compose.

Question 16

If you use LiveData in Jetpack Compose, how must it be converted for Compose to use it?

Accepted Answer

It must be converted to State by calling the observeAsState() function.

Question 17

Why are Lazy Lists used instead of standard Columns for large amounts of data?

Accepted Answer

They do not load all items into memory at once; they load them in a lazy way only when they scroll into view.

Question 18

What composable function is used to create a vertical scrollable lazy list?

Accepted Answer

LazyColumn

Question 19

What composable function is used to create a horizontal scrollable lazy list?

Accepted Answer

LazyRow

Question 20

What domain-specific DSL functions are used inside a LazyColumn to add a single item and multiple items?

Accepted Answer

item{} to add a single item, and items{} to add multiple items.

Question 21

Which function creates an observable instance of MutableList that allows Compose to track list additions and deletions?

Accepted Answer

mutableStateListOf()

Question 22

To fix a compatibility issue with using Instant in DatePicker on SDK 24, what change must be made in build.gradle.kts?

Accepted Answer

Change the minSdk version to 26 and sync the project.

Question 23

By default, why does the DatePicker use the US date format?

Accepted Answer

Because its Locale parameter is set to US by default.

Question 24

How can you configure the DatePicker to display dates in the Australian format?

Accepted Answer

By setting the Locale parameter explicitly to Australia.

FIT5046 - Week 3: Jetpack Compose State, ViewModels, and Lazy Lists

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