Revise paste App Android video 06

package com.example.convertitoreculinario

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.width
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.ArrowDropDown
import androidx.compose.material3.Button
import androidx.compose.material3.DropdownMenu
import androidx.compose.material3.DropdownMenuItem
import androidx.compose.material3.Icon
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import com.example.convertitoreculinario.ui.theme.ConvertitoreCulinarioTheme

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            ConvertitoreCulinarioTheme {
                Surface(modifier = Modifier.fillMaxSize()) {
                    ConvertitoreCulinario()
                }
            }
        }
    }
}

@Composable
fun ConvertitoreCulinario() {
    var daSrotolata = remember { mutableStateOf(false) }
    var aSrotolata = remember { mutableStateOf(false) }

var inputCasella = remember { mutableStateOf(value="") }

var daUnita = remember { mutableStateOf(value="") }
    var aUnita = remember { mutableStateOf(value="") }

var conversione = remember { mutableStateOf(value="") }

fun Converti() : String {
        val input = inputCasella.value.toDoubleOrNull() ?: 0.0

val risultatoConversione = when (daUnita.value) {
            "Tazze" -> when (aUnita.value) {
                "ml" -> input * 200
                "grammi" -> input * 125
                else -> ""
            }

"Bicchieri" -> when (aUnita.value) {
                "ml" -> input * 200
                "grammi" -> input * 125
                else -> ""
            }

"Cucchiai" -> when (aUnita.value) {
                "ml" -> input * 200
                "grammi" -> input * 125
                else -> ""
            }

else -> ""
        }

return risultatoConversione.toString()
    }

Column(
        modifier = Modifier.fillMaxSize(),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally
    ) {

Text("Convertitore Culinario", style = MaterialTheme.typography.headlineLarge)
        Spacer(modifier = Modifier.height(16.dp))

OutlinedTextField(
            value = inputCasella.value,
            onValueChange = {
                inputCasella.value = it
                conversione.value = Converti()
            },
            label = {Text("Enter Value") })

Spacer(modifier = Modifier.height(16.dp))

Row {
            Box {

Button(onClick = { daSrotolata.value = true }) {
                    Text(text = daUnita.value)
                    Icon(
                        Icons.Default.ArrowDropDown,
                        contentDescription = "Freggia giú"
                    )  //accessibilitá ...
                }

DropdownMenu(expanded = daSrotolata.value, onDismissRequest = {
                             daSrotolata.value = false})
                {
                    DropdownMenuItem(
                        text = { Text("Tazze") },
                        onClick = {
                            daSrotolata.value = false
                            daUnita.value = "Tazze"
                            conversione.value = Converti()
                        }
                    )

DropdownMenuItem(
                        text = { Text("Cucchiai") },
                        onClick = {
                            daSrotolata.value = false
                            daUnita.value = "Cucchiai"
                            conversione.value = Converti()
                        }
                    )

DropdownMenuItem(
                        text = { Text("Bicchieri") },
                        onClick = {
                            daSrotolata.value = false
                            daUnita.value = "Bicchieri"
                            conversione.value = Converti()
                        }
                    )
                }
            }

Spacer(modifier = Modifier.width(16.dp))

Box {
                Button(onClick = {aSrotolata.value = true }) {
                    Text(text = aUnita.value)
                    Icon(
                        Icons.Default.ArrowDropDown,
                        contentDescription = "Freggia giú"
                    )  //accessibilitá ...
                }

DropdownMenu(expanded = aSrotolata.value, onDismissRequest = {
                    aSrotolata.value = false
                }) {

DropdownMenuItem(
                        text = { Text("ml") },
                        onClick = {
                            aSrotolata.value = false
                            aUnita.value = "ml"
                            conversione.value = Converti()
                        }
                    )

DropdownMenuItem(
                        text = { Text("grammi") },
                        onClick = {
                            aSrotolata.value = false
                            aUnita.value = "grammi"
                            conversione.value = Converti()
                        }
                    )
                }

}

}
        Spacer(modifier = Modifier.height(30.dp))
        Text("Pari a:" + conversione.value,
            style = MaterialTheme.typography.headlineMedium
        )
    }
}

@Preview(showBackground = true)
@Composable
fun ConvertitoreCulinarioPreview() {
    ConvertitoreCulinarioTheme {
        ConvertitoreCulinario()
    }
}