Why architecture scales codebases in Android Kotlin - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a ViewModel class in Kotlin.

Android Kotlin

class MainViewModel : [1]() {
    // ViewModel logic here
}

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

AViewModel

BFragment

CActivity

DService

Attempts:

3 left

💡 Hint

Common Mistakes

Using Activity or Fragment instead of ViewModel.

Confusing Service with ViewModel.

The ViewModel class helps keep UI data separate from UI controllers, which is key for scalable architecture.

2fill in blank

medium

Complete the code to observe LiveData in an Activity.

Android Kotlin

viewModel.data.observe([1]) { value ->
    // update UI with value
}

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Athis

BlifecycleOwner

CviewLifecycleOwner

Dcontext

Attempts:

3 left

💡 Hint

Common Mistakes

Using viewLifecycleOwner which is for Fragments.

Passing lifecycleOwner without context.

In an Activity, you pass 'this' as the LifecycleOwner to observe LiveData.

3fill in blank

hard

Fix the error in the repository pattern code by completing the interface declaration.

Android Kotlin

interface [1] {
    fun getUser(id: String): User
}

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AUserDataSource

BUserViewModel

CUserService

DUserRepository

Attempts:

3 left

💡 Hint

Common Mistakes

Naming it UserViewModel which is for UI logic.

Using UserService which is more network related.

The repository interface is commonly named UserRepository to abstract data operations.

4fill in blank

hard

Fill both blanks to complete the ViewModel factory code for dependency injection.

Android Kotlin

class [1](private val repository: [2]) : ViewModel() {
    // ViewModel code
}

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AMainViewModel

BUserRepository

CUserService

DMainActivity

Attempts:

3 left

💡 Hint

Common Mistakes

Using MainActivity as class name instead of ViewModel.

Injecting UserService directly instead of repository.

The ViewModel class is named MainViewModel and it takes UserRepository as a dependency.

5fill in blank

hard

Fill all three blanks to complete the Kotlin code for a simple MVVM data flow.

Android Kotlin

class [1](private val [2]: [3]) : ViewModel() {
    val data = MutableLiveData<String>()
}

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

AUserViewModel

Brepository

CUserRepository

DMainActivity

Attempts:

3 left

💡 Hint

Common Mistakes

Using MainActivity as class name.

Naming the repository parameter incorrectly.

The ViewModel is UserViewModel, it has a repository property of type UserRepository injected.