How to Fix the Most Frequent Issues in Kotlin Coroutines

In this post, we will explore real-world problems developers face when using Kotlin Coroutines. Every issue is explained with a clear example and then followed by a simple fix. Let’s dive in.

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1. Blocking the Main Thread with `runBlocking`

Using runBlocking in the wrong place can freeze your UI or crash your app.

fun loadUserData() {
    runBlocking { val user = fetchUser() println (user) }
}

Problem: This blocks the main thread. If you call this in an Android activity or ViewModel, your UI can freeze.

Solution Use a proper coroutine scope like viewModelScope or lifecycleScope.

fun loadUserData() {
    viewModelScope.launch { val user = fetchUser() println (user) }
} 

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2. Not Handling Exceptions Properly

Coroutines throw exceptions just like regular code. But if you're not careful, your app can silently crash.

viewModelScope.launch { 
   val data = fetchData() // throws exception showData(data)
} 

Problem: No try-catch block. If fetchData fails, your coroutine cancels and nothing is shown to the user.

Solution Wrap it in a try-catch to handle the error gracefully.

 
viewModelScope.launch { 
    try {
        val data = fetchData() 
        showData(data) 
    } catch (e: Exception) { 
        showError("Something went wrong") 
    }
} 

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3. Launching Too Many Coroutines

It's tempting to launch a coroutine for every task. But this can lead to memory leaks or app slowdown.

repeat(1000) { 
    GlobalScope.launch { 
        delay(1000) 
        println("Coroutine $it") 
    } 
}

Problem: You're launching 1000 coroutines. This can eat up memory or crash the app.

Solution Use structured concurrency with a proper scope.

lifecycleScope.launch { 
    repeat(1000) { 
        delay(1000) 
        println("Task $it") 
    } 
}

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4. Using `withContext` Inside Loops Inefficiently

Switching threads too much inside a loop slows things down.

items.forEach { 
    withContext(Dispatchers.IO) { 
        processItem(it) 
    } 
} 

Problem: You're switching context on every item. That's a performance hit.

Solution Move the whole loop inside one context switch.

 
withContext(Dispatchers.IO) { 
    items.forEach { 
        processItem(it) 
    } 
} 

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5. Forgetting to Cancel Long-Running Jobs

Coroutines can keep running in the background if you forget to cancel them.

 
val job = CoroutineScope(Dispatchers.IO).launch { 
    doHeavyTask() 
}

Problem: This coroutine will keep running unless you cancel it manually.

Solution Use rememberCoroutineScope() in Compose or structured scopes that cancel automatically.

val scope = rememberCoroutineScope() 
val job = scope.launch { 
    doHeavyTask() 
} 

// call job.cancel() when needed 

Wrap Up

These are some of the most common coroutine mistakes developers make in real Android projects. Keep your coroutines structured, scoped, and always handle exceptions. If you want to learn more, follow our video tutorials for deeper dives and clean code practices.