Challenge 3: Migrate to View Binding — Solution

// app/build.gradle.kts
android {
    // ...existing config...
    buildFeatures {
        viewBinding = true
    }
}

// MainActivity.kt (using the layout from Challenge 2 — a ConstraintLayout
// with nameLabel, nameInput, and submitButton IDs)
class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        binding.submitButton.setOnClickListener {
            val name = binding.nameInput.text.toString()
            binding.nameLabel.text = "Hello, $name!"
        }
    }
}

Notes:
- After enabling viewBinding and rebuilding (Gradle sync), Android
  Studio generates ActivityMainBinding automatically from
  activity_main.xml — no manual class-writing needed, and no
  findViewById calls remain anywhere in MainActivity.
- binding.root refers to the layout's root ConstraintLayout itself,
  passed to setContentView the same way R.layout.activity_main was
  passed directly in earlier chapters.
- binding.nameInput and binding.submitButton are both correctly typed
  (EditText and Button respectively) purely from their XML tag and id —
  autocomplete surfaces exactly the members each type actually has, with
  no manual casting required.
- If nameInput or submitButton were ever renamed or removed from the
  XML without updating MainActivity.kt, this code would fail to compile
  immediately, rather than crashing later at runtime the way a stale
  findViewById("wrong_id") call would.