class MainActivity : ComponentActivity() {

     override fun onCreate(savedInstanceState: Bundle?) {
          super.onCreate(savedInstanceState)
          setContent {
               Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
               ) {
                    Greeting()
               }
          }
     }

}

@Composable
fun Greeting() {
     Text(
          text = "Hello Android!"
     )
}

class MainActivity : AppCompatActivity() {

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

}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context=".MainActivity">

     <TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Hello World!"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintEnd_toEndOf="parent"
          app:layout_constraintStart_toStartOf="parent"
          app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

setContent {
     Surface(
          modifier = Modifier.fillMaxSize(),
          color = MaterialTheme.colorScheme.background
     ) {
          Greeting()
     }
}

fun main() {

     setContent {
          Surface(
               color = "green"
          )
          {
               Text("Hello!")
               Text("I want coffee :)")
               Text("Thank you")
          }
     }
}

fun setContent(myFunc1:() -> Unit)
{
     myFunc1();
}

fun Surface(color:String, myFunc2:() -> Unit)
{
     println("┌---------------------------------")
     println("|")
     println("|")

     myFunc2();

     println("|")
     println("|")
     println("└---------------------------------")
}

fun Text(description:String)
{
     println("| $description ");
}