Managing Activity Lifecycle

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

    override fun onStart() {
        super.onStart()
        // Prepare for interaction
    }

    override fun onResume() {
        super.onResume()
        // Register listeners or start animations
    }

    override fun onPause() {
        super.onPause()
        // Save persistent state
    }

    override fun onStop() {
        super.onStop()
        // Release heavy resources
    }

    override fun onDestroy() {
        super.onDestroy()
        // Cleanup all resources
    }
}

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

        // Initialize views and set up listeners
        val textView = findViewById<TextView>(R.id.textView)
        textView.text = "Hello, Android!"
    }
}

class MainActivity : AppCompatActivity() {
    private var isActivityVisible = false

    override fun onStart() {
        super.onStart()
        isActivityVisible = true
        Log.d("MainActivity", "Activity started")
    }

    override fun onStop() {
        super.onStop()
        isActivityVisible = false
        Log.d("MainActivity", "Activity stopped")
    }
}

class MainActivity : AppCompatActivity() {
    private var isPaused = false

    override fun onResume() {
        super.onResume()
        isPaused = false
        // Resume any paused operations or UI updates
        Log.d("Lifecycle", "Activity resumed")
    }

    override fun onPause() {
        super.onPause()
        isPaused = true
        // Save data or release resources
        Log.d("Lifecycle", "Activity paused")
    }
}

class MainActivity : AppCompatActivity() {
    private var timer: Timer? = null

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

        timer = Timer()
        timer?.scheduleAtFixedRate(object : TimerTask() {
            override fun run() {
                // Background task
            }
        }, 0, 1000)
    }

    override fun onDestroy() {
        super.onDestroy()
        timer?.cancel()
        timer = null
    }
}

class MainActivity : AppCompatActivity() {
    override fun onConfigurationChanged(newConfig: Configuration) {
        super.onConfigurationChanged(newConfig)
        if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
            // Handle landscape mode
        } else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) {
            // Handle portrait mode
        }
    }
}

<activity
    android:name=".MainActivity"
    android:configChanges="orientation|screenSize|keyboardHidden">
</activity>

class MainActivity : AppCompatActivity() {
    private var count = 0

    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        outState.putInt("count", count)
    }

    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
        super.onRestoreInstanceState(savedInstanceState)
        count = savedInstanceState.getInt("count", 0)
    }
}

override fun onSaveInstanceState(outState: Bundle) {
    super.onSaveInstanceState(outState)
    outState.putString("userInput", userInputEditText.text.toString())
}

override fun onRestoreInstanceState(savedInstanceState: Bundle) {
    super.onRestoreInstanceState(savedInstanceState)
    userInputEditText.setText(savedInstanceState.getString("userInput"))
}

import androidx.lifecycle.Lifecycle.Event
import androidx.lifecycle.LifecycleObserver
import androidx.lifecycle.OnLifecycleEvent

class MyObserver : LifecycleObserver {
    @OnLifecycleEvent(Event.ON_START)
    <span class="hljs-function>fun onStart() {
        println("Activity started")
    }

    @OnLifecycleEvent(Event.ON_STOP)
    <span class="hljs-function>fun onStop</span>() {
        println("Activity stopped")
    }
}

class MainActivity : AppCompatActivity() {
    private val observer = MyObserver()

    @Override
    <span class="hljs-function>fun onCreate</span>(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        supportFragmentManager.registerFragmentLifecycleCallbacks(
            object : FragmentLifecycleCallbacks() {
                <span class="hljs-function>override fun onFragmentCreated</span>(fm: FragmentManager, f: Fragment, savedInstanceState: Bundle?) {
                    f.lifecycle.addObserver(observer)
                }
            }, false
        )
    }
}

<activity
    android:name=".MainActivity"
    android:launchMode="singleTask" />

<activity
    android:name=".MainActivity"
    android:predictiveBackGestureEnabled="true">
</activity>

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

        // Enable edge-to-edge display
        WindowCompat.setDecorFitsSystemWindows(window, false)
    }
}

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

        // Set status bar color to transparent
        WindowCompat.setDecorFitsSystemWindows(window, false)
        window.statusBarColor = Color.TRANSPARENT
    }
}