Fix Kotlin Coroutine Crash: Main Dispatcher Not Found

If you’re working with Kotlin Coroutines in Android Studio and encounter the error:

IllegalStateException: Module with the Main dispatcher is missing. 
Add dependency providing the Main dispatcher, e.g., kotlinx-coroutines-android

you’re not alone. This error occurs when your project is missing the Android-specific coroutine dispatcher that handles tasks on the Main (UI) thread. In this guide, you’ll learn how to fix it with complete and working code examples.

Why This Error Happens

The Main dispatcher is required when you use:

withContext(Dispatchers.Main) { ... }

Without the proper dependency (kotlinx-coroutines-android), the app crashes at runtime because it cannot find the necessary module to handle the Main thread.

How to Fix It

Step 1: Add Required Dependency

Open your build.gradle file (app-level) and make sure you have the following:

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3'

Replace 1.7.3 with the latest version if needed.

Sync your project after adding the dependency.

Working Example: Coroutine in ViewModel

MainActivity.kt

class MainActivity : AppCompatActivity() {
    private lateinit var viewModel: MainViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        viewModel = ViewModelProvider(this)[MainViewModel::class.java]
        viewModel.loadData()
    }
}

MainViewModel.kt

class MainViewModel : ViewModel() {
    fun loadData() {
        viewModelScope.launch {
            withContext(Dispatchers.Main) {
                // Your UI-related code here
                Log.d("Coroutine", "Running on Main Thread")
            }
        }
    }
}

Pro Tips

• Always include kotlinx-coroutines-android when using Dispatchers.Main
• Check Gradle sync status if the issue persists
• Avoid using Dispatchers.Main in plain Kotlin/JVM modules — it’s meant for Android

External Resource

For more on coroutine setup, see the official Kotlin documentation: Kotlin Coroutine Guide

Summary

The “Main Dispatcher Not Found” error in Kotlin Coroutines is common but easy to fix. By adding the right coroutine dependency for Android, your Dispatchers.Main calls will work flawlessly. Use kotlinx-coroutines-android and make sure your Gradle setup is correct.