Coroutine context and dispatchers in Kotlin - Mini Project: Build & Apply

Coroutine Context and Dispatchers

📖 Scenario: You are building a simple Kotlin program that uses coroutines to perform tasks on different threads. This helps your app stay responsive by running work in the background.

🎯 Goal: Learn how to set up coroutine contexts and use dispatchers to control which thread your coroutine runs on.

📋 What You'll Learn

Create a coroutine scope with a specific dispatcher

Launch coroutines using different dispatchers

Print the thread name inside each coroutine to see where it runs

💡 Why This Matters

🌍 Real World

In real apps, using coroutine contexts and dispatchers helps keep the user interface smooth by running heavy tasks on background threads.

💼 Career

Understanding coroutine dispatchers is important for Kotlin developers working on Android or server applications to write efficient, responsive code.

1

Create a CoroutineScope with Dispatchers.Default

Create a variable called scope and assign it a CoroutineScope using Dispatchers.Default as the context.

Kotlin

# Create a CoroutineScope called scope with Dispatchers.Default
# Your code here

Need a hint?

Use CoroutineScope(Dispatchers.Default) to create the scope.

2

Launch a Coroutine on Dispatchers.IO

Using the scope variable, launch a coroutine with Dispatchers.IO as the context. Inside the coroutine, print the current thread name using Thread.currentThread().name.

Kotlin

import kotlinx.coroutines.*

val scope = CoroutineScope(Dispatchers.Default)

// Launch a coroutine on Dispatchers.IO and print the thread name
# Your code here

Need a hint?

Use scope.launch(Dispatchers.IO) { ... } and print the thread name inside.

3

Launch a Coroutine on Dispatchers.Main

Using the scope variable, launch another coroutine with Dispatchers.Main as the context. Inside this coroutine, print the current thread name using Thread.currentThread().name.

Kotlin

import kotlinx.coroutines.*

val scope = CoroutineScope(Dispatchers.Default)

scope.launch(Dispatchers.IO) {
    println("Running on thread: ${Thread.currentThread().name}")
}

// Launch a coroutine on Dispatchers.Main and print the thread name
# Your code here

Need a hint?

Use scope.launch(Dispatchers.Main) { ... } and print the thread name inside.

4

Run the Program and Print Completion Message

Add a runBlocking block to wait for the launched coroutines to finish. Inside runBlocking, launch the two coroutines again and then print "All coroutines completed" after they finish.

Kotlin

import kotlinx.coroutines.*

val scope = CoroutineScope(Dispatchers.Default)

// Use runBlocking to wait for coroutines
fun main() = runBlocking {
    // Launch coroutine on Dispatchers.IO
    // Launch coroutine on Dispatchers.Main
    // Print completion message
    # Your code here
}

Need a hint?

Use runBlocking with launch and join() to wait for coroutines, then print the message.