Dispatchers.Main, IO, Default behavior in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to launch a coroutine on the main thread.

Kotlin

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

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

AMain

BDefault

CUnconfined

DIO

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.IO for UI updates causes errors because it's for background work.

Using Dispatchers.Default does not guarantee running on the main thread.

Dispatchers.Main is used to run coroutines on the main thread, which is necessary for UI updates.

2fill in blank

medium

Complete the code to perform a network request on the appropriate dispatcher.

Kotlin

CoroutineScope(Dispatchers.[1]).launch {
    val data = fetchData()
    // process data
}

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

AIO

BMain

CDefault

DUnconfined

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.Main for network calls can freeze the UI.

Dispatchers.Default is for CPU-intensive tasks, not IO.

Dispatchers.IO is optimized for blocking IO tasks like network or disk operations.

3fill in blank

hard

Fix the error in the code to run a CPU-intensive task on the correct dispatcher.

Kotlin

CoroutineScope(Dispatchers.[1]).launch {
    val result = heavyComputation()
    // use result
}

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

AMain

BDefault

CIO

DUnconfined

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.IO for CPU tasks can cause thread starvation.

Using Dispatchers.Main for heavy work blocks the UI.

Dispatchers.Default is optimized for CPU-intensive tasks like heavy computations.

4fill in blank

hard

Fill both blanks to create a coroutine that switches from IO to Main dispatcher.

Kotlin

CoroutineScope(Dispatchers.[1]).launch {
    val data = fetchData()
    withContext(Dispatchers.[2]) {
        updateUI(data)
    }
}

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

AIO

BMain

CDefault

DUnconfined

Attempts:

3 left

💡 Hint

Common Mistakes

Not switching back to Main dispatcher before UI update.

Using Default dispatcher for IO tasks.

Start on Dispatchers.IO for background work, then switch to Dispatchers.Main to update UI.

5fill in blank

hard

Fill all three blanks to create a coroutine that performs CPU work, then IO, then updates UI.

Kotlin

CoroutineScope(Dispatchers.[1]).launch {
    val cpuResult = heavyComputation()
    val ioResult = withContext(Dispatchers.[2]) {
        fetchData()
    }
    withContext(Dispatchers.[3]) {
        updateUI(cpuResult, ioResult)
    }
}

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

ADefault

BIO

CMain

DUnconfined

Attempts:

3 left

💡 Hint

Common Mistakes

Using Main dispatcher for CPU or IO tasks.

Not switching dispatchers properly causing UI freezes.

Use Default for CPU work, switch to IO for network, then Main for UI updates.