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Table of contents
1.
Introduction
2.
LiveData Coroutine Builder
3.
Why we need coroutines?
4.
Kotlin Coroutines Features
5.
Kotlin Coroutines vs Threads
6.
What is Kotlin Flow?
7.
Kotlin flow to LiveData
8.
Properties of Flow:
9.
Why we use flow over channels?
10.
Try to expose streams as Flows and not Channels
11.
Frequently Asked Questions
11.1.
How many types of coroutines are there in Kotlin?
11.2.
What is the difference between threads and coroutines in Kotlin?
11.3.
What are the disadvantages of coroutines?
12.
Conclusion
Last Updated: Mar 27, 2024
Medium

Introduction to Kotlin Coroutines

Author Urwashi Priya
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Introduction

Kotlin Coroutines have revolutionized asynchronous programming in the world of Kotlin. With its elegant and powerful features, coroutines have become popular for handling asynchronous tasks, concurrency, and simplifying code structures. 

coroutines kotlin

In this article, we will explore the fundamentals of Kotlin Coroutines, their advantages, and how they can make your asynchronous code more efficient and readable.

LiveData Coroutine Builder

The entire coroutine itself as a code block is relayed to the liveData () builder function as an argument. The code block is not enclosed with parenthesis as Kotlin enables us to skip the parenthesis when a code block is dynamically altering, by using LiveData Coroutine along with a switchMap() function. In many cases, developers trigger the coroutine only when the value of LiveData is altered. For instance, whenever an ID is a prerequisite for launching a data load.

There is also another coroutine library for representing asynchronous sequences, or audio and video streams of values known as the Coroutines Asynchronous Flow.
You can build your first Android App with Kotlin, read this blog to know more.

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Why we need coroutines?

There are various reasons why we need coroutines:

  • Coroutines offer a systematic and user-friendly solution to asynchronous programming, enabling non-blocking task execution and obviating the need for intricate callbacks or chaining promises.
  • Concurrent execution is made possible by coroutines because it eliminates the need to create and maintain numerous threads. Because they may operate in a single thread, they can make better use of system resources and minimize context switching.
  • Coroutines use sequential programming structures like 'if', 'for', and 'while' loops to streamline the code, making asynchronous code easier to comprehend and maintain.
  • Coroutines may handle long-running or blocking activities effectively by supporting suspending functions that can be paused and restarted without interrupting the main thread.
  • Coroutines offer a centralized method for handling exceptions, allowing mistakes to spread throughout the hierarchy of coroutines and streamlining error handling and recovery.

Kotlin Coroutines Features

Some of the Kotlin Coroutines Features include:

  • Coroutines are lightweight since they don't need to create and maintain many threads because they can be run on a single thread.
  • Coroutines support the idea of organized concurrency by ensuring that any child coroutines are terminated automatically if the parent coroutine is terminated or experiences an error.
  • For the creation and administration of coroutines, Kotlin has two constructors: "launch" and "async." You have the freedom to manage many coroutines and their return values thanks to these constructs.
  • Coroutine scopes, which specify a coroutine's lifetime and context, enable the orderly administration and termination of coroutines.
  • Dispatchers control the thread or thread pool on which a coroutine is executed as well as other configuration options in the context of a coroutine.

Kotlin Coroutines vs Threads

Kotlin Coroutines vs Threads:

  • Lightweight: Coroutines are more lightweight than threads, as they can run on a single thread and avoid the overhead of creating and managing multiple threads.
  • Concurrency: Coroutines provide concurrency without needing multiple threads, allowing for efficient and concurrent execution of tasks.
  • Structured Concurrency: Coroutines follow the principle of structured concurrency, ensuring proper management and cancellation of child coroutines.
  • Simplified Code: Coroutines simplify asynchronous code using sequential programming constructs, making the code more readable and maintainable than thread-based code.
  • Exception Handling: Coroutines provide a unified exception-handling mechanism, making handling and propagating exceptions in asynchronous code easier. Threads require explicit error-handling mechanisms.

What is Kotlin Flow?

Kotlin Flow is a contemporary stream processing API (Application user interface). The idea for Kotlin Flow comes from Reactive Stream specification, which is an initiative taken to set a uniform standard for asynchronous stream processing.

Analogous to coroutines Kotlin Flow was also developed by the JetBrains, one of the top-notch companies and the developer of Kotlin language also. That’s why the entire concept of Kotlin Flow is based on the structure of Kotlin Coroutines. To structure your data in a complex multi-threaded way with a concise and brief code you may use Kotlin Flow to handle a stream of values.

Kotlin flow is a sequential process, which includes the following steps:

  • Data extraction and data streaming.
  • Invoking synchronous and asynchronous APIs.
  • Streaming Hot and cold data.
  • With the help of try and catch, handling the exceptions amidst data flow.

Here are some features of Kotlin & Kotlinx to understand their difference.

Kotlin flow to LiveData

You can know more about advanced coroutines with Kotlin Flow and LiveData and include the logical aspect of your code in a LiveData builder. Kotlin Coroutines 1.2.0 comes up with a cold stream called Flow. Kotlin Flow is used for carrying out asynchronous operations. If you try to blend and encapsulate some of the Kotlin Flows, you may transform multiple asynchronous sources.

The most crucial task in mobile development is transferring data, it is achieved by Control concurrency LiveData. Apart from transferring data in a unique way, Kotlin flow also performs async operations. Further exploring LiveData and Kotlin Flow, Kotlin Flow transfers encapsulated data by converting them into an existing LiveData by exploiting the Kotlin coroutines-friendly LiveData builder. You may include the logical segments of the code within a LiveData builder. It makes the co-ordination among UI and ViewModel easier, on the logic designed by you.

kotlin flow to live data

Image Source: Medium

By combining Kotlin Coroutines Flow, LiveData and Data Binding you can perform asynchronous operations. Although it is true that Flow is part of Kotlin and LiveData is part of the androidx.lifecycle library yet Flow can be used as an integral component of the uses cases in a clear architecture, without the requirement of any supplementary dependencies. In contrast to Kotlin Flow, LiveData is aware of the life cycle, so it overlaps the ViewModel.

5 Best server-side Kotlin frameworks you should be working on

Properties of Flow:

Context Preservation and Backpressure: Flow possesses a unique property known as context preservation., which implies a set of Flow always takes place in the context of the parent coroutine. You may alter the property later while emitting items. The flowOn() function can be used for changing the context of emissions.

Sometimes you can have some unusual scenarios such as a Flow may produce events too fast, so the collector is unable to consume them. This is known as backpressure, in reactive streams. Kotlin Flow supports backpressure extraordinary as it is based on coroutines. The producer has the ability to recognize whether the consumer is busy doing some work or is in the suspended state. At such instances, the producer doesn’t produce any items and waits until the consumer becomes active.

Exceptions: Flow streams end up throwing exceptions if any emitter or codes encapsulated within operators throw an exception. Similar to Java, catch() blocks are used to handle exceptions within Flow also. This can be done in two ways, imperatively or declaratively.

A very widespread example of the imperative approach is the try-catch block on the collector’s side. It is considered to be imperative as these catch the entire range of exceptions that are initialized in the emitter or in any of the operators. While for handling errors declaratively catch() can be used. By declarative, we mean that you have to declare a function to deal with the errors. In cases of Flow, you can declare the catch() within the flow, you don’t need to embrace it with a try-catch block.

Cancellations: You can observe the forecasts in Model.kt. You must be wondering that for how long you may observe this. As soon as the LiveData becomes active the Flow collection begins. In such cases, if LiveData turns inactive prior to the Flow completion, the flow collection gets cancelled. The cancelled is triggered after a specifically timed delay unless LiveData turns active again prior to the timeout.5000 milliseconds is the default delay triggering cancellation.

You can overwrite the timeout value according to your requirements. Android configuration changes can be handled efficiently by using such timeouts. If LiveData turns active again post-cancellation, the Flow collection is resumed.

Searching Locations: Currently, your app displays a forecast for a hardcoded location. But now by implementing coroutines and Flow you can allow the user to look for a particular location. The app performs a detailed scan for each alphabet entered by the user and updates the results simultaneously as the user types in the search box.

In the MainActivity.kt, you can create a listener and link it with the search view. As soon as the user alters the query text, the app pushes the new value forward to the query channel in Model.kt. The class Model.kt passes the text from the view to the ViewModel by using a BroadcastChannel as a bridge. The text is passed as well as the specific element is added synchronously to the channel by using offer().

Why we use flow over channels?

The Android Developers’ Summit (ADS) app was declared  as an open-source in 2019, it allows us to handle data streams with its multiple layers by exploiting flows in the best manner. The ADS app keeps each of its class concise, dedicated, reusable and testable by using a supplementary domain layer (of Use Cases) that deals with separate issues. Analogous to several high computing Android apps, the ADS app efficiently fetches data from the network classes or the cache memory; this feature can serve as a perfect use case for Flow.

use case for Flow

Image Source: Medium

Suspend functions were a better fit for single-step operations. App refractors to use Coroutines due to two main commits that migrate to two different strategies, the first one migrate to one-shot operations while the second one migrates to data streams.

Developers are restricted to a set of principles for refactoring the app from using LiveData in all layers of the architecture. They are allowed to resort to LiveData just for establishing communication between View and ViewModel, the sub-layers of the architecture and Coroutines for the Use Case.

use case for Flow

Image Source: Androiexample365

Try to expose streams as Flows and not Channels

There are two ways of manipulating streams of data in coroutines:

  • Flow API
  • Channel API

Channels are considered to be synchronization primitives while Flow is created for building model streams of data, it can be considered as a warehouse for availing data stream subscriptions. Furthermore, channels are employed for supporting Flows.

Flow is highly preferred by developers as it allows higher flexibility, more operators, and explicit contacts in comparison to channels.

Due to the properties of terminal operators that invokes the execution of a data streams and completes them successfully or exceptionally based on the entire range of flow operations in the producer end, flows automatically locks the stream of data.

Read about Shrinking Kotlin libraries & apps using Reflection with R8

 It almost inhibits the leakage of resources at the producer end. Channels are vulnerable to such attacks, the producers might not give up the heavy resources in case the channel is not locked properly. Every app has a data layer which is responsible for allocating data by fetching it from the database or the web, it is known as the data layer.

For instance, the code snippet given below depicts a DataSource interface that exposes a stream of user event data:

interface UserEventDataSource
{
    fun getObservableUserEvent(userId: String): Flow
}

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Frequently Asked Questions

How many types of coroutines are there in Kotlin?

In Kotlin, there are two types of coroutines: `launch` and `async`. The `launch` coroutine is used for fire-and-forget asynchronous operations, while `async` is used for operations that return a result, allowing you to await the result.

What is the difference between threads and coroutines in Kotlin?

The main difference between threads and coroutines is that the operating system manages threads, while the Kotlin runtime manages coroutines. Coroutines can be executed on a single thread, allowing for efficient and concurrent execution without the overhead of creating and managing multiple threads.

What are the disadvantages of coroutines?

Disadvantages of coroutines include potential blocking operations that may suspend the entire coroutine, which requires careful consideration of which operations can be safely performed asynchronously. Additionally, improper usage of coroutines can lead to complex code structures and potential for coroutine leaks if not properly managed.

Conclusion

Kotlin has an upper hand in the Android industry not only because of its compatibility with ios but also for its advanced features such as Kotlin Coroutines along with Flow and LiveData, which saves a lot of developers’ time and provides a better overall user experience. By knowing the properties of Flow and the use of LiveData you can implement coroutines in a better way, by co-ordinating among the three.

Check out this article - Balanced Parentheses

ADS app was declared as an open-source so that the developers can learn the implement strategies without any abstraction and customise the default methods according to the requisites and scalability of the project on which they are working.

To read more articles on Android, click here.

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