Challenge 1: Navigate Between Two Activities — Solution

// res/layout/activity_detail.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/detailText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="This is the Detail screen" />

</LinearLayout>

// DetailActivity.kt
class DetailActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_detail)
    }
}

// AndroidManifest.xml — inside <application>, alongside MainActivity's entry
<activity android:name=".DetailActivity" />

// MainActivity.kt — inside onCreate, after binding is set up
binding.goToDetailButton.setOnClickListener {
    val intent = Intent(this, DetailActivity::class.java)
    startActivity(intent)
}

Notes:
- DetailActivity must be registered in AndroidManifest.xml, or
  startActivity() will crash with an ActivityNotFoundException even
  though the Kotlin class itself compiles fine.
- Intent(this, DetailActivity::class.java) is an EXPLICIT Intent — it
  names the exact destination Activity directly, unlike the implicit
  Intents covered later in the chapter.
- Tapping the button pushes MainActivity to onPause/onStop (per Chapter
  2's lifecycle) while DetailActivity runs onCreate/onStart/onResume.