async/await | Coroutines | Kotlin

async/await | Coroutines | Kotlin

async/await | Coroutines

• async/await simplifies asynchronous code, making it easier to read and maintain.
• Coroutines execute long-running tasks without blocking the main thread or freezing the UI.
• async launches a coroutine and returns a Deferred object; await retrieves the result.
• The exceptions can be handled with try/catch or onFailure to prevent crashes and unexpected behavior.

Scratch.kts file

import com.hacoga.asyncawait.Post
import kotlinx.coroutines.*
import kotlinx.serialization.decodeFromString
import kotlinx.serialization.json.Json
import java.net.URL
import kotlin.coroutines.CoroutineContext

requestPosts() // Output: Posts count: 100

// Request posts
fun requestPosts() = runBlocking {
    val sample = Sample(coroutineContext)
    val posts = sample.fetchAsync().await()
    println("Posts count: " + posts.count())
}

class Sample(override val coroutineContext: CoroutineContext)
    : CoroutineScope {
    fun fetchAsync() = async { fetchPosts() }
    // Fetch posts
    private fun fetchPosts(): Array<Post> {
        val url = "https://jsonplaceholder.typicode.com/posts"
        val json = URL(url).readText()
        return Json.decodeFromString<Array<Post>>(json)
    }
}

MainActivity.kts file

package com.hacoga.asyncawait

import android.os.Bundle
import android.provider.ContactsContract.CommonDataKinds.Website.URL
import com.google.android.material.snackbar.Snackbar
import androidx.appcompat.app.AppCompatActivity
import androidx.navigation.findNavController
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.navigateUp
import androidx.navigation.ui.setupActionBarWithNavController
import android.view.Menu
import android.view.MenuItem
import com.hacoga.asyncawait.databinding.ActivityMainBinding
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch
import kotlinx.coroutines.*
import kotlinx.serialization.Serializable
import java.net.URL

@Serializable
data class Post(val userId: Int,
                val id: Int,
                val title: String,
                val body: String)

class MainActivity : AppCompatActivity() {

    private lateinit var appBarConfiguration: AppBarConfiguration
    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        setSupportActionBar(binding.toolbar)

        val navController = findNavController(R.id.nav_host_fragment_content_main)
        appBarConfiguration = AppBarConfiguration(navController.graph)
        setupActionBarWithNavController(navController, appBarConfiguration)

        binding.fab.setOnClickListener { view ->
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                .setAction("Action", null).show()
        }
    }

}

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