launch and async builders in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

Android Kotlin

GlobalScope.[1] {
    println("Hello from coroutine")
}

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

Alaunch

Basync

CrunBlocking

Ddelay

Attempts:

3 left

💡 Hint

Common Mistakes

Using async instead of launch when no result is needed.

Using delay as a builder, which is a suspending function.

The launch builder starts a new coroutine without blocking the current thread.

2fill in blank

medium

Complete the code to start an async coroutine that returns a value.

Android Kotlin

val deferred = GlobalScope.[1] {
    delay(1000)
    return@[1] 42
}

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

Aasync

Blaunch

CrunBlocking

DwithContext

Attempts:

3 left

💡 Hint

Common Mistakes

Using launch when a result is needed.

Using runBlocking inside GlobalScope.

The async builder starts a coroutine and returns a Deferred which holds a future result.

3fill in blank

hard

Fix the error in the code by choosing the correct coroutine builder.

Android Kotlin

val result = GlobalScope.[1] {
    delay(500)
    10 + 20
}
println(result.await())

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Aproduce

Basync

CrunBlocking

Dlaunch

Attempts:

3 left

💡 Hint

Common Mistakes

Using launch and trying to call await() on Job.

Using runBlocking inside GlobalScope.

Only async returns a Deferred that supports await() to get the result.

4fill in blank

hard

Fill both blanks to create a coroutine that launches and then waits for an async result.

Android Kotlin

GlobalScope.[1] {
    val deferred = async {
        delay(300)
        5 * 5
    }
    val result = deferred.[2]()
    println(result)
}

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Alaunch

Basync

Cawait

Djoin

Attempts:

3 left

💡 Hint

Common Mistakes

Using async for the outer coroutine when launch is better for fire-and-forget.

Using join() instead of await() to get the result.

Use launch to start the coroutine and await to get the async result.

5fill in blank

hard

Fill all three blanks to create an async coroutine that returns a computed value after delay.

Android Kotlin

val deferred = GlobalScope.[1] {
    delay(200)
    val x = 10
    val y = 20
    x [2] y
}
println(deferred.[3]())

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

Aasync

B+

Cawait

Dlaunch

Attempts:

3 left

💡 Hint

Common Mistakes

Using launch instead of async when a result is needed.

Using join() instead of await() to get the result.

Use async to start coroutine returning a value, + to add, and await to get the result.