State in ViewModel in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a mutable state variable in ViewModel.

Android Kotlin

private val _count = MutableStateFlow([1])
val count: StateFlow<Int> = _count

Drag options to blanks, or click blank then click option'

Afalse

B""

C0

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using empty string "" instead of 0 for an integer state.

Using null which is not allowed without nullable type.

Using false which is a Boolean, not an Int.

We initialize the mutable state with 0 because count is an integer.

2fill in blank

medium

Complete the code to update the state value inside ViewModel.

Android Kotlin

fun increment() {
  _count.value = _count.value [1] 1
}

Drag options to blanks, or click blank then click option'

A+

B-

C+=

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+=' which is not valid for StateFlow value assignment.

Using '-' or '*' which change the value incorrectly.

We add 1 to the current value to increment the count.

3fill in blank

hard

Fix the error in the ViewModel state declaration.

Android Kotlin

class CounterViewModel : ViewModel() {
  private val _count = MutableStateFlow<Int>([1])
  val count: StateFlow<Int> = _count
}

Drag options to blanks, or click blank then click option'

Anull

Bfalse

C"0"

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using null which causes a runtime error.

Using string "0" which is not an Int.

Using false which is a Boolean.

MutableStateFlow requires a non-null initial value matching the type Int, so 0 is correct.

4fill in blank

hard

Fill both blanks to create a function that resets the count to zero.

Android Kotlin

fun reset() {
  _count.[1] = [2]
}

Drag options to blanks, or click blank then click option'

Avalue

B0

Cnull

Demit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'emit' which is a suspend function and cannot be called directly here.

Assigning null which is not allowed for non-nullable Int state.

We assign 0 to the value property of _count to reset the state.

5fill in blank

hard

Fill all three blanks to create a ViewModel with a mutable state and a function to decrement the count.

Android Kotlin

class CounterViewModel : ViewModel() {
  private val _count = MutableStateFlow([1])
  val count: StateFlow<Int> = [2]

  fun decrement() {
    _count.value = _count.value [3] 1
  }
}

Drag options to blanks, or click blank then click option'

A0

B_count

C-

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Exposing 'count' instead of '_count' for the public state.

Using '+' instead of '-' for decrement.

Initializing with a wrong type.

The state starts at 0, the public state is _count, and decrement subtracts 1.