Challenge 2: repeatOnLifecycle in an Activity — Solution

class MainActivity : AppCompatActivity() {
    private val viewModel: TaskViewModel by viewModels()
    private lateinit var statusText: TextView

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

        lifecycleScope.launch {
            repeatOnLifecycle(Lifecycle.State.STARTED) {
                viewModel.uiState.collect { state ->
                    statusText.text = "Loading: ${state.isLoading}"
                }
            }
        }
    }
}

// What would happen without repeatOnLifecycle (collecting the Flow
// directly instead):
//
// If the code instead did "lifecycleScope.launch { viewModel.uiState.collect
// { ... } }" with no repeatOnLifecycle wrapper, the collection would keep
// running continuously for as long as the Activity instance exists —
// including while the app is fully backgrounded (past onStop, per
// Course 1 Chapter 2). Every emission from uiState would still trigger
// the collect block's work (here, a View update) even though the screen
// isn't visible to update at all, which is genuinely wasted CPU work,
// and in a real app could mean wasted battery or unnecessary continued
// processing tied to state the user can't currently see anyway.
// repeatOnLifecycle(STARTED) fixes this by cancelling and restarting the
// collection automatically as the Activity crosses the STARTED
// threshold, so collection only ever runs while genuinely visible.

Notes:
- lifecycleScope.launch { repeatOnLifecycle(...) { ... } } is the
  standard nesting — repeatOnLifecycle itself is a suspend function that
  needs to run inside a coroutine, which is what the outer
  lifecycleScope.launch provides.
- This entire pattern is exactly what collectAsStateWithLifecycle()
  handles internally in Compose — this challenge is intentionally the
  "manual" version, for code still using the traditional View system
  from Course 1.