CoroutineScope and dispatchers in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to launch a coroutine in the Main dispatcher.

Android Kotlin

CoroutineScope(Dispatchers.[1]).launch {
    // UI update code here
}

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ADefault

BIO

CMain

DUnconfined

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.IO for UI updates causes errors.

The Main dispatcher runs coroutines on the main thread, suitable for UI updates.

2fill in blank

medium

Complete the code to switch context to a background thread for heavy work.

Android Kotlin

withContext(Dispatchers.[1]) {
    // heavy computation
}

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AMain

BDefault

CUnconfined

DIO

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.Main blocks UI thread.

Default dispatcher is optimized for CPU-intensive work on background threads.

3fill in blank

hard

Fix the error in the coroutine scope declaration to use the IO dispatcher.

Android Kotlin

val scope = CoroutineScope(Dispatchers.[1])

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AIO

BDefault

CMain

DUnconfined

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.Main for IO causes blocking UI.

IO dispatcher is used for blocking IO tasks like file or network operations.

4fill in blank

hard

Fill both blanks to create a CoroutineScope with a Job and the Default dispatcher.

Android Kotlin

val job = Job()
val scope = CoroutineScope(job + Dispatchers.[1])
scope.launch {
    // work
}
job.[2]()

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ADefault

Bcancel

CMain

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using start() instead of cancel() on Job.

The scope uses Default dispatcher and the job is cancelled with cancel() to stop coroutines.

5fill in blank

hard

Fill all three blanks to launch a coroutine on the IO dispatcher and switch to Main for UI update.

Android Kotlin

CoroutineScope(Dispatchers.[1]).launch {
    val data = fetchData()
    withContext(Dispatchers.[2]) {
        updateUI(data)
    }
}
fun fetchData() = "Data"
fun updateUI(data: String) {
    println("UI updated with $[3]")
}

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

AMain

BIO

Cdata

DDefault

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up dispatchers or printing wrong variable.

The coroutine starts on IO for background work, switches to Main for UI update, and prints the data string.