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danielcristho/MainActivity.kt

Created April 15, 2025 02:25
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Currency Converter
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MainActivity.kt
package com.example.currencyconversion
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.*
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.ArrowDropDown
import androidx.compose.material.icons.filled.Refresh
import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clip
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.*
import com.example.currencyconversion.ui.theme.CurrencyConversionTheme
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
CurrencyConversionTheme {
Surface(modifier = Modifier.fillMaxSize()) {
CurrencyConverter()
}
}
}
}
}
// Pindahkan data kurs ke bagian data statis
private val EXCHANGE_RATES = mapOf(
"IDR" to 1.0,
"USD" to 16823.0,
"EUR" to 19150.0,
"JPY" to 117.06,
"SGD" to 12570.0,
"AUD" to 11350.0,
"GBP" to 22450.0,
"CHF" to 19750.0,
"CAD" to 12400.0,
"CNY" to 2418.0
)
@Composable
fun CurrencyConverter() {
val currencies = remember { listOf("IDR", "USD", "EUR", "JPY", "SGD", "AUD", "GBP", "CHF", "CAD", "CNY") }
var amountInput by remember { mutableStateOf("") }
var fromCurrency by remember { mutableStateOf("IDR") }
var toCurrency by remember { mutableStateOf("USD") }
// Warna tema
val primaryColor = MaterialTheme.colorScheme.primary
val surfaceColor = MaterialTheme.colorScheme.surfaceVariant
// Menggunakan debounce untuk mengurangi perhitungan berulang
val debouncedAmountFlow = remember {
MutableStateFlow("")
}
val debouncedAmount by produceState("") {
debouncedAmountFlow
.debounce(300)
.collect { value = it }
}
// Update flow saat input berubah
LaunchedEffect(amountInput) {
debouncedAmountFlow.value = amountInput
}
// Menyimpan hasil konversi dengan remember untuk mengurangi perhitungan berulang
val convertedAmount by remember(debouncedAmount, fromCurrency, toCurrency) {
derivedStateOf {
val amount = debouncedAmount.toDoubleOrNull() ?: 0.0
convertCurrency(amount, fromCurrency, toCurrency)
}
}
Column(
modifier = Modifier
.fillMaxSize()
.padding(16.dp),
verticalArrangement = Arrangement.spacedBy(16.dp)
) {
Card(
modifier = Modifier.fillMaxWidth(),
elevation = CardDefaults.cardElevation(defaultElevation = 2.dp)
) {
Column(
modifier = Modifier.padding(16.dp),
horizontalAlignment = Alignment.CenterHorizontally
) {
Text(
"Currency Converter",
style = MaterialTheme.typography.headlineMedium,
fontWeight = FontWeight.Bold
)
Spacer(modifier = Modifier.height(4.dp))
Text(
"Convert between world currencies",
style = MaterialTheme.typography.bodyMedium,
color = MaterialTheme.colorScheme.onSurfaceVariant
)
}
}
Spacer(modifier = Modifier.height(8.dp))
// Input card
Card(
modifier = Modifier.fillMaxWidth(),
colors = CardDefaults.cardColors(containerColor = surfaceColor)
) {
Column(
modifier = Modifier.padding(16.dp),
verticalArrangement = Arrangement.spacedBy(16.dp)
) {
OutlinedTextField(
value = amountInput,
onValueChange = {
// Validasi input: hanya terima angka dan titik desimal
if (it.isEmpty() || it.matches(Regex("^\\d*\\.?\\d*$"))) {
amountInput = it
}
},
label = { Text("Amount") },
singleLine = true,
modifier = Modifier.fillMaxWidth(),
shape = RoundedCornerShape(8.dp)
)
Row(
modifier = Modifier.fillMaxWidth(),
horizontalArrangement = Arrangement.SpaceBetween,
verticalAlignment = Alignment.CenterVertically
) {
// From Currency
ImprovedCurrencyDropdown(
label = "From",
selectedCurrency = fromCurrency,
onCurrencySelected = { fromCurrency = it },
currencies = currencies,
modifier = Modifier.weight(1f)
)
// Swap Button
TextButton(
onClick = {
val temp = fromCurrency
fromCurrency = toCurrency
toCurrency = temp
},
modifier = Modifier.padding(horizontal = 4.dp)
) {
Text(
text = "⇄",
style = MaterialTheme.typography.titleLarge,
color = primaryColor
)
}
// To Currency
ImprovedCurrencyDropdown(
label = "To",
selectedCurrency = toCurrency,
onCurrencySelected = { toCurrency = it },
currencies = currencies,
modifier = Modifier.weight(1f)
)
}
}
}
Spacer(modifier = Modifier.height(8.dp))
// Result card
Card(
modifier = Modifier.fillMaxWidth(),
colors = CardDefaults.cardColors(
containerColor = primaryColor.copy(alpha = 0.1f)
),
elevation = CardDefaults.cardElevation(defaultElevation = 2.dp)
) {
Column(
modifier = Modifier
.fillMaxWidth()
.padding(16.dp),
horizontalAlignment = Alignment.CenterHorizontally
) {
Text(
text = "Result",
style = MaterialTheme.typography.titleMedium,
color = MaterialTheme.colorScheme.onSurfaceVariant
)
Spacer(modifier = Modifier.height(8.dp))
Text(
text = String.format("%.2f", convertedAmount),
style = MaterialTheme.typography.headlineMedium,
fontWeight = FontWeight.Bold
)
Text(
text = toCurrency,
style = MaterialTheme.typography.titleMedium,
color = primaryColor
)
}
}
Spacer(modifier = Modifier.weight(1f))
// Footer with exchange rate info
if (fromCurrency != toCurrency) {
val rate = getExchangeRate(fromCurrency, toCurrency)
Text(
text = "Exchange Rate: 1 $fromCurrency = ${String.format("%.4f", rate)} $toCurrency",
style = MaterialTheme.typography.bodySmall,
color = MaterialTheme.colorScheme.onSurfaceVariant,
modifier = Modifier.align(Alignment.CenterHorizontally)
)
}
}
}
@Composable
fun ImprovedCurrencyDropdown(
label: String,
selectedCurrency: String,
onCurrencySelected: (String) -> Unit,
currencies: List<String>,
modifier: Modifier = Modifier
) {
var expanded by remember { mutableStateOf(false) }
Column(modifier = modifier) {
Text(
text = label,
style = MaterialTheme.typography.bodyMedium,
color = MaterialTheme.colorScheme.onSurfaceVariant
)
Spacer(modifier = Modifier.height(4.dp))
Box {
Button(
onClick = { expanded = true },
modifier = Modifier
.fillMaxWidth()
.height(48.dp)
.clip(RoundedCornerShape(8.dp)),
colors = ButtonDefaults.buttonColors(
containerColor = MaterialTheme.colorScheme.primary.copy(alpha = 0.2f),
contentColor = MaterialTheme.colorScheme.primary
)
) {
Row(
modifier = Modifier.fillMaxWidth(),
horizontalArrangement = Arrangement.SpaceBetween,
verticalAlignment = Alignment.CenterVertically
) {
Text(
text = selectedCurrency,
fontWeight = FontWeight.Bold
)
Icon(
Icons.Default.ArrowDropDown,
contentDescription = "Select currency"
)
}
}
DropdownMenu(
expanded = expanded,
onDismissRequest = { expanded = false },
modifier = Modifier.width(IntrinsicSize.Min)
) {
currencies.forEach { currency ->
DropdownMenuItem(
text = { Text(currency) },
onClick = {
onCurrencySelected(currency)
expanded = false
}
)
}
}
}
}
}
fun getExchangeRate(from: String, to: String): Double {
val rateFrom = EXCHANGE_RATES[from] ?: 1.0
val rateTo = EXCHANGE_RATES[to] ?: 1.0
return rateFrom / rateTo
}
fun convertCurrency(amount: Double, from: String, to: String): Double {
// Jika mata uang sama, tidak perlu konversi
if (from == to) return amount
// Konversi langsung: from -> IDR -> to
val rateFrom = EXCHANGE_RATES[from] ?: 1.0
val rateTo = EXCHANGE_RATES[to] ?: 1.0
val amountInIDR = amount * rateFrom
return amountInIDR / rateTo
}
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