Challenge 2: Surviving Rotation with savedInstanceState — Solution

// activity_main.xml needs a Button with an id, e.g. android:id="@+id/clickButton"

class MainActivity : AppCompatActivity() {
    private var clickCount: Int = 0

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

        clickCount = savedInstanceState?.getInt("clickCount") ?: 0
        Log.d("MainActivity", "onCreate: clickCount restored to $clickCount")

        val button = findViewById<Button>(R.id.clickButton)
        button.setOnClickListener {
            clickCount++
            Log.d("MainActivity", "Button clicked, clickCount = $clickCount")
        }
    }

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

Walkthrough:
1. Add the Button to activity_main.xml (a simple <Button> with an
   android:id) and the code above to MainActivity.kt.
2. Run the app, click the button 3-4 times, watching Logcat count up.
3. Rotate the emulator.
4. Check Logcat: the "onCreate: clickCount restored to N" line should
   show the SAME count you'd reached before rotating, not 0.

Notes:
- clickCount = savedInstanceState?.getInt("clickCount") ?: 0 uses the
  safe-call + Elvis pattern from Kotlin Fundamentals Chapter 3: if
  savedInstanceState is null (a genuinely fresh launch), the ?: 0
  fallback kicks in; if it holds a saved Bundle, getInt("clickCount")
  retrieves the saved value.
- onSaveInstanceState only runs before a RECOVERABLE destruction (like
  rotation) — pressing Back to close the app entirely does not call it,
  since there's nothing meaningful to restore into afterward.