course on Kotlin Android App Development, Activity ANR Issues and Coroutines

Performance is a crucial factor in Android app development. To improve user experience, the responsiveness of the application is essential. This article will explain the ANR (Application Not Responding) issue and how to solve it using Kotlin’s coroutines in detail.

1. What is the ANR (Application Not Responding) Issue?

ANR occurs when the app’s UI does not respond for more than 5 seconds while the user is using the app. In this case, the user feels as if the app has frozen, and the system automatically shows a dialog stating “The app is not responding.” The main causes of ANR are as follows:

• Performing heavy tasks on the main (UI) thread
• Response delays due to blocked threads
• Synchronization issues between UI updates and data processing

1.1 Example of ANR

For instance, if a user clicks a button and a network request or a database query is executed on the main thread, ANR can occur. The following is a simple code example that can induce ANR:

class MainActivity : AppCompatActivity() {
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)

            val button = findViewById(R.id.button)
            button.setOnClickListener {
                // Long task that causes ANR
                performLongTask()
            }
        }

        private fun performLongTask() {
            // Sleep for 5 seconds
            Thread.sleep(5000) // This causes ANR
        }
    }

2. Introduction to Coroutines

Coroutines are lightweight threads designed to make asynchronous programming easier. By using coroutines, you can keep your code concise and readable while handling long tasks simultaneously. Coroutines can run tasks separately from the main thread, making them very useful for preventing ANR.

2.1 Advantages of Coroutines

• Allows intuitive handling of asynchronous tasks
• Reduces the complexity of thread management
• Improves reusability and ease of testing

2.2 Example of Using Coroutines

Below is an example of code that uses coroutines to handle long tasks asynchronously:

import kotlinx.coroutines.*

    class MainActivity : AppCompatActivity() {
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)

            val button = findViewById(R.id.button)
            button.setOnClickListener {
                // Perform long task using coroutines
                performLongTaskInCoroutine()
            }
        }

        private fun performLongTaskInCoroutine() {
            // Define a scope to start the coroutine
            lifecycleScope.launch {
                // Asynchronous task
                delay(5000) // Wait for 5 seconds
                // Update UI after task completion
                Toast.makeText(this@MainActivity, "Task Completed!", Toast.LENGTH_SHORT).show()
            }
        }
    }

3. Setting Up Coroutines

To use coroutines, you need to add the required dependencies to Gradle. Modify your build.gradle file to add the coroutine library as follows:

dependencies {
        implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.5.2'
        implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.2'
    }

4. CoroutineScope and LifecycleScope

Coroutines need to be executed within a specific scope. In Android, you can manage coroutines using CoroutineScope and LifecycleScope. The lifecycleScope manages the lifecycle of Activities and Fragments well, allowing for safer operations during UI updates.

4.1 Example of Using CoroutineScope

You can utilize CoroutineScope for asynchronous processing, as shown below:

class MainActivity : AppCompatActivity(), CoroutineScope {
        // Set default dispatcher
        private val job = Job()
        override val coroutineContext: CoroutineContext
            get() = Dispatchers.Main + job

        override fun onDestroy() {
            super.onDestroy()
            job.cancel() // Clean up coroutines when the Activity is destroyed
        }

        // Asynchronous processing method
        private fun performAsyncTask() {
            launch {
                // Asynchronous task
                withContext(Dispatchers.IO) {
                    // Example of a long task
                    delay(2000)
                }
                // Update UI on the main thread
                Toast.makeText(this@MainActivity, "Processing Complete", Toast.LENGTH_SHORT).show()
            }
        }
    }

5. Using Coroutines to Prevent ANR

Based on what has been explained so far, you can properly utilize coroutines to solve ANR issues. Below is an example of avoiding ANR problems through a network call:

class MainActivity : AppCompatActivity() {
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)

            val button = findViewById(R.id.button)
            button.setOnClickListener {
                fetchDataFromNetwork()
            }
        }

        private fun fetchDataFromNetwork() {
            lifecycleScope.launch {
                val result = withContext(Dispatchers.IO) {
                    // Simulated network request
                    simulateNetworkRequest()
                }
                // Update UI
                Toast.makeText(this@MainActivity, "Result: $result", Toast.LENGTH_SHORT).show()
            }
        }

        private suspend fun simulateNetworkRequest(): String {
            delay(3000) // 3 seconds delay
            return "Data Load Complete"
        }
    }

6. Conclusion

In this article, we explored the ANR issue and the use of coroutines to solve it in depth. By utilizing coroutines, you can reduce the burden on the UI thread and provide a better experience for users. We encourage you to actively use coroutines to improve both app performance and user experience. We hope this article has been helpful for your Android app development.

7. Additional Resources

Below are links to additional resources on coroutines, ANR, and Android app development:

• Kotlin Coroutines Official Documentation
• Android Coroutines Guide
• Android StrictMode Documentation

If you have questions or feedback, please leave a comment!