Mobile Application Lifecycle and State Preservation Questions

// Launch activity, input data, move to background, kill process, relaunch, assert restored state

val controller = Robolectric.buildActivity(MyActivity::class.java).create().start().resume()
controller.pause().stop().destroy()
val recreated = Robolectric.buildActivity(MyActivity::class.java).create().start().resume()

adb shell am start -n com.example/.MainActivity
adb shell input keyevent KEYCODE_APP_SWITCH
adb shell am kill com.example.myapp   # kills process
adb shell monkey -p com.example.myapp -c android.intent.category.LAUNCHER 1

let app = XCUIApplication(); app.terminate(); app.launch()

xcrun simctl spawn booted notify_post com.apple.simulator.memoryWarning

xcrun simctl spawn booted killall YourAppExecutableName

class MyWorker(private val callbackRef: WeakReference<(Result) -> Unit>) {
  fun doWork() {
    // heavy work...
    callbackRef.get()?.invoke(result) // safe, may be null
  }
}

lifecycleScope.launch {
  // work scoped to Activity/Fragment lifecycle
}

class _MyState extends State<MyWidget> with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    // init controllers/subscriptions
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    // dispose controllers/subscriptions
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.paused) { /* save minimal state */ }
    if (state == AppLifecycleState.resumed) { /* refresh resources */ }
    if (state == AppLifecycleState.detached) { /* final cleanup if needed */ }
  }
}

class CounterActivity : AppCompatActivity() {
    companion object {
        private const val KEY_COUNT = "key_count"
    }

    private var count = 0
    private lateinit var countText: TextView
    private lateinit var incButton: Button

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_counter)
        countText = findViewById(R.id.countText)
        incButton = findViewById(R.id.incButton)

        // Read/restoring the counter from the savedInstanceState bundle (if available)
        count = savedInstanceState?.getInt(KEY_COUNT, 0) ?: 0
        updateUi()

        incButton.setOnClickListener {
            count++
            updateUi()
        }
    }

    // Write/persist the counter into outState bundle before possible process death
    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        outState.putInt(KEY_COUNT, count)
    }

    private fun updateUi() {
        countText.text = count.toString()
    }
}