Best Practices for Handling Errors in Kotlin Compose

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When building Android apps with Kotlin and Jetpack Compose, error handling is critical in ensuring a smooth and robust user experience. Something will inevitably go wrong in any application—whether it's a network failure, API error, or unexpected runtime exception—and how you handle these errors can make or break your app.

In this blog post, we'll explore best practices for handling errors in Kotlin Compose. We’ll break down various approaches for dealing with errors and provide examples that can be easily implemented into your Compose-based Android apps.

Why Error Handling Matters

Error handling is about more than just preventing crashes. It's about gracefully managing unexpected situations and providing users with meaningful feedback. Effective error handling leads to:

  • Improved user experience: Users aren't left in the dark when something goes wrong.
  • Increased app stability: By handling errors, you prevent crashes and ensure your app remains functional even in failure scenarios.
  • Better debugging: When you can catch and log errors, you can quickly identify issues and fix them.

In Kotlin Compose, handling errors properly involves managing UI states (such as loading, success, and error) and informing users about the issue with appropriate messages.

Best Practices for Error Handling in Kotlin Compose

  1. Use Sealed Classes to Represent UI States Using sealed classes is a great way to represent different states in your application, such as loading, success, and error. This pattern keeps your code clean and predictable by clearly defining each state's meaning.

  2. Handle Network and API Errors Gracefully Always check the response from an API call. Handle HTTP errors like 404, 500, etc., and ensure you provide meaningful error messages to the user.

  3. Catch Exceptions for Unexpected Scenarios Unexpected exceptions such as network timeouts or parsing issues can occur during runtime. Using try-catch blocks ensures that these errors don’t crash the app, and you can show a user-friendly error message instead.

  4. Show Loading States Displaying a loading indicator while data is being fetched or processed helps to manage user expectations. It signals that the app is working on an operation and is responsive even when the user has to wait.

  5. Provide a Retry Mechanism for Recoverable Errors Some errors, like network failures, might be temporary and can be fixed by retrying the operation. Offering a retry button or a similar mechanism helps users recover from these errors without leaving the app.

Example of Handling Errors in Kotlin Compose

Let’s take a practical example of fetching user data from a REST API and handling various types of errors, such as network issues, API errors, and null responses.

Step 1: Set up Retrofit for API Calls

interface ApiService {
    @GET("users/{id}")
    suspend fun getUser(@Path("id") id: Int): Response<User>
}

Step 2: Create a ViewModel to Manage UI States

We’ll use sealed classes to represent different states: loading, success, and error.

class UserViewModel : ViewModel() {
    private val _state = mutableStateOf<UserState>(UserState.Loading)
    val state: State<UserState> = _state

    fun getUser(id: Int) {
        viewModelScope.launch {
            _state.value = UserState.Loading
            try {
                // Make network request
                val response = ApiClient.apiService.getUser(id)

                // Handle API response
                if (response.isSuccessful) {
                    val user = response.body()
                    if (user != null) {
                        _state.value = UserState.Success(user)
                    } else {
                        _state.value = UserState.Error("No user data found")
                    }
                } else {
                    // Handle API error codes like 404, 500
                    _state.value = UserState.Error("API Error: ${response.code()}")
                }
            } catch (e: Exception) {
                // Handle network errors or unexpected exceptions
                _state.value = UserState.Error("Network Error: ${e.localizedMessage}")
            }
        }
    }
}

sealed class UserState {
    object Loading : UserState()
    data class Success(val user: User) : UserState()
    data class Error(val message: String) : UserState()
}

Step 3: Displaying the UI Based on State

In the Compose UI, we will observe the state and update the UI based on whether it's in the loading, success, or error state.

@Composable
fun UserScreen(userViewModel: UserViewModel) {
    val state by userViewModel.state.observeAsState(UserState.Loading)

    when (state) {
        is UserState.Loading -> {
            // Show loading indicator
            CircularProgressIndicator()
        }
        is UserState.Success -> {
            // Show user data
            val user = (state as UserState.Success).user
            Text("User Name: ${user.name}")
            Text("User Email: ${user.email}")
        }
        is UserState.Error -> {
            // Show error message
            val errorMessage = (state as UserState.Error).message
            Text("Error: $errorMessage", color = Color.Red)
            // Optionally, add a retry button here
            Button(onClick = { userViewModel.getUser(1) }) {
                Text("Retry")
            }
        }
    }
}

@Composable
fun UserScreenWithButton(userViewModel: UserViewModel) {
    Column {
        Button(onClick = { userViewModel.getUser(1) }) {
            Text("Get User")
        }
        UserScreen(userViewModel)
    }
}

Error Scenarios and How to Handle Them

1. Network Errors

Network issues are common in mobile applications. This can happen due to no internet connection, slow network, or server unavailability. In such cases, we catch the exception and display an error message.

catch (e: Exception) {
    _state.value = UserState.Error("Network Error: ${e.localizedMessage}")
}

For example, if the device is offline or the request times out, the error message could look like:

Network Error: java.net.UnknownHostException: Unable to resolve host "api.example.com"

2. API Errors (HTTP Status Codes)

The server might return different HTTP status codes such as 404 (Not Found), 500 (Internal Server Error), or others. We need to handle these cases gracefully by checking the response code.

if (!response.isSuccessful) {
    _state.value = UserState.Error("API Error: ${response.code()}")
}

For example, a 404 error could result in the message:

API Error: 404

3. Null Responses

Sometimes, the server might return a 200 OK response, but the response body could be null. It’s essential to handle these cases by checking for null data and updating the state accordingly.

if (user == null) {
    _state.value = UserState.Error("No user data found")
}

In this case, the message could be:

No user data found

4. Unexpected Exceptions

Unexpected issues, such as JSON parsing errors or null pointer exceptions, can occur. We should always catch such exceptions to prevent crashes.

catch (e: Exception) {
    _state.value = UserState.Error("Unexpected Error: ${e.localizedMessage}")
}

This could result in messages like:

Unexpected Error: java.lang.NullPointerException

Summary

Error handling is essential to building stable and reliable Android applications. Best practices, such as using sealed classes to represent different UI states, handling API errors, catching exceptions, and providing meaningful feedback to users, can help you build a more robust and user-friendly app.

Remember to always:

  • Represent UI states clearly using sealed classes.
  • Gracefully handle network and API errors with proper messages.
  • Display loading states to manage user expectations.
  • Provide a retry mechanism for recoverable errors.

Implementing these best practices in your Kotlin Compose apps will create a more stable, resilient, and user-friendly user experience.

📢 Feedback: Did you find this article helpful? Let me know your thoughts or suggestions for improvements! 😊 please leave a comment below. I’d love to hear from you! 👇

Happy coding! 💻✨


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