📍 Introduction
Welcome to Day 6 of the HandsOnAndroid 90-Day Challenge!
Understanding the Android Activity Lifecycle is crucial for building stable apps. Lifecycle methods determine how your app behaves during screen rotations, incoming calls, or app switching. Mastering these will help you write responsive, memory-efficient Android apps.
🔄 What is the Activity Lifecycle?
The Activity Lifecycle represents the different states an Activity goes through — from creation to destruction — as the user navigates your app or system events occur.
🧩 Complete Android Lifecycle Methods Explained
| Lifecycle Method | When It’s Called | Typical Usage Example |
|---|---|---|
onCreate() | Activity is first created | Set up UI, initialize components |
onStart() | Activity becomes visible to user | Start animations, prepare UI |
onResume() | Activity is in foreground and interactive | Resume media, start sensors |
onPause() | Partial visibility (e.g., new activity on top) | Pause animations, save unsaved changes |
onStop() | Activity no longer visible | Release camera/audio resources, unregister listeners |
onRestart() | Activity returns to foreground from onStop() | Reinitialize components or UI |
onDestroy() | Activity is about to be destroyed (user/system-initiated) | Clean up resources, avoid memory leaks |
onSaveInstanceState() | System might destroy your activity (e.g., rotation) | Save temporary UI state to Bundle |
onRestoreInstanceState() | After onStart() if a saved state was provided | Restore UI data like text fields or scroll positions |
🧪 Sample Code in Kotlin
kotlinCopyEditoverride fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
Log.d("Lifecycle", "onCreate")
}
override fun onStart() {
super.onStart()
Log.d("Lifecycle", "onStart")
}
override fun onResume() {
super.onResume()
Log.d("Lifecycle", "onResume")
}
override fun onPause() {
super.onPause()
Log.d("Lifecycle", "onPause")
}
override fun onStop() {
super.onStop()
Log.d("Lifecycle", "onStop")
}
override fun onRestart() {
super.onRestart()
Log.d("Lifecycle", "onRestart")
}
override fun onDestroy() {
super.onDestroy()
Log.d("Lifecycle", "onDestroy")
}
👉 Use Logcat to observe how lifecycle methods behave during app minimization, screen rotation, or activity switching.
✅ Pro Tips for Lifecycle Handling
- ⏳ Save critical data: Use
onSaveInstanceState()to persist temporary user data. - 🔋 Free up resources: Stop sensors or network calls in
onPause()oronStop(). - 🚫 Prevent memory leaks: Always unregister observers, coroutines, or listeners in
onDestroy().