LiveData basics in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a LiveData variable named data of type String.

Android Kotlin

val data: LiveData<[1]> = MutableLiveData()

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

AInt

BString

CBoolean

DFloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong data type like Int when you want to hold text.

Forgetting to specify the type inside the angle brackets.

LiveData holds data of a specific type. Here, we want it to hold strings, so we use LiveData.

2fill in blank

medium

Complete the code to observe the LiveData data inside an Activity and update a TextView when data changes.

Android Kotlin

data.observe(this, [1] { newValue -> textView.text = newValue })

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

Aobserve

BobserveForever

CobserveData

DObserver

Attempts:

3 left

💡 Hint

Common Mistakes

Using observeForever inside an Activity which can cause memory leaks.

Passing a wrong method name like observeData.

To observe LiveData changes, you pass an Observer object that reacts to updates.

3fill in blank

hard

Fix the error in this code that tries to update LiveData value inside a ViewModel.

Android Kotlin

private val _data = MutableLiveData<String>()
val data: LiveData<String> = _data

fun updateData(newValue: String) {
  _data.[1] = newValue
}

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

Avalue

BsetValue

CupdateValue

DpostValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using postValue on the main thread when setValue or value assignment is preferred.

Trying to call a method named updateValue which does not exist.

To update LiveData value on the main thread, assign the new value to the 'value' property.

4fill in blank

hard

Fill both blanks to create a LiveData that transforms another LiveData's data by converting it to uppercase.

Android Kotlin

val originalData: LiveData<String> = MutableLiveData()
val upperData: LiveData<String> = Transformations.[1](originalData) { it.[2]() }

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

Amap

BswitchMap

CtoUpperCase

Duppercase

Attempts:

3 left

💡 Hint

Common Mistakes

Using switchMap instead of map when only transforming data.

Using the deprecated 'toUpperCase()' method.

Use Transformations.map to create a LiveData that applies a function to the original data. The modern Kotlin method to convert to uppercase is 'uppercase()'.

5fill in blank

hard

Fill all three blanks to create a ViewModel with MutableLiveData, expose it as LiveData, and update its value safely.

Android Kotlin

class MyViewModel : ViewModel() {
  private val _count = MutableLiveData<Int>().apply { value = [1] }
  val count: LiveData<Int> = [2]

  fun increment() {
    val current = _count.value ?: 0
    _count.[3] = current + 1
  }
}

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

A0

B_count

Cvalue

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Exposing the MutableLiveData directly instead of as LiveData.

Using the wrong property or method to update the LiveData value.

Initialize MutableLiveData with 0, expose it as LiveData by returning _count, and update the value property to increment.