Coroutines in Kotlin: A Guide to Asynchronous and Non-blocking Programming

Coroutines are a concurrency design pattern that you can use in Kotlin to simplify code that executes asynchronously. Coroutines are based on established concepts from other languages, but are fully supported by the Kotlin language and the Kotlin compiler.

Coroutines allow you to write code that looks like synchronous or blocking code, but actually runs asynchronously or non-blocking on a different thread. This means that you can perform long-running tasks, such as network requests, database operations, or complex computations, without blocking the main thread and causing your app to freeze or crash.

Coroutines also provide other benefits, such as:

• Lightweight: You can run many coroutines on a single thread, because they use suspension instead of blocking. Suspension means that a coroutine can pause its execution at some point and resume later, without consuming any resources while waiting.
• Cancellation support: You can easily cancel a coroutine if it is no longer needed, and the cancellation will propagate automatically to any other coroutines that depend on it.
• Jetpack integration: Many Jetpack libraries, such as Room, WorkManager, Paging, and Lifecycle, provide extensions or annotations that make it easy to use coroutines with them.

To use coroutines in Kotlin, you need to follow these steps:

• Add the coroutines dependencies to your project’s build.gradle file.
• Use the suspend modifier to mark a function as a suspending function, which means that it can be paused and resumed by a coroutine.
• Use the coroutineScope function to create a scope for your coroutines, which defines their lifecycle and cancellation policy.
• Use the launch or async functions to start a coroutine within the scope, and pass a lambda expression with the code that you want to run asynchronously.
• Use the await function to get the result of an async coroutine, or use the join function to wait for a launch coroutine to finish.
• Use the withContext function to switch the context of a coroutine, which means changing the thread or dispatcher that it runs on.

For example, you can create a simple app that makes a network request using coroutines:

First, you need to add the coroutines dependencies to your project’s build.gradle file:

dependencies {
    ...
    // Coroutines core
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.5.2"
    // Coroutines Android
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.2"
}

Then, you need to create a suspending function that makes the network request using Retrofit:

suspend fun fetchUser(id: Int): User {
    return Retrofit.Builder()
        .baseUrl("https://example.com")
        .build()
        .create(UserService::class.java)
        .getUser(id)
}

Next, you need to create a coroutine scope for your activity or fragment using the lifecycleScope extension from the lifecycle-runtime-ktx library:

val scope = lifecycleScope

After that, you need to launch a coroutine within the scope and call the suspending function:

scope.launch {
    val user = fetchUser(1)
    // Update UI with user data
}

Alternatively, you can use the viewModelScope extension from the lifecycle-viewmodel-ktx library to create a coroutine scope for your view model:

val scope = viewModelScope

If you want to learn more about coroutines in Kotlin and how to use them for asynchronous and non-blocking programming, you can check out the following resources:

• Android Developers guide on Kotlin coroutines
• Kotlin documentation on coroutines

Coroutines in Kotlin are a powerful and elegant way to write asynchronous and non-blocking code. With coroutines skills, you can build better apps faster and easier. So what are you waiting for? Start suspending today!