PPB - Tugas 5

Nama : Ahmad Hafiz Mahardika

NRP : 5025201196

Kelas : Pemrograman Perangkat Bergerak (B)

Implementasi Aplikasi Kalkulator Sederhana

MainActivity.kt

package com.example.calculator

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.annotation.StringRes
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.text.KeyboardOptions
import androidx.compose.material3.Button
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.material3.TextField
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.res.stringResource
import androidx.compose.ui.text.input.ImeAction
import androidx.compose.ui.text.input.KeyboardType
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import com.example.calculator.ui.theme.CalculatorTheme
import java.text.NumberFormat

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            CalculatorTheme {
                Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
                    CalculatorLayout(modifier = Modifier.padding(innerPadding))
                }
            }
        }
    }
}

@Composable
fun CalculatorLayout(modifier: Modifier = Modifier) {
    var firstNumber by remember { mutableStateOf("") }
    var secondNumber by remember { mutableStateOf("") }
    var result by remember { mutableStateOf("") }

    val onButtonClick = { operator: String ->
        result = calculateResult(firstNumber, secondNumber, operator)
    }

    Column(
        modifier = modifier
            .fillMaxSize()
            .padding(horizontal = 40.dp),
        horizontalAlignment = Alignment.CenterHorizontally,
        verticalArrangement = Arrangement.Center
    ) {
        Text(
            text = stringResource(R.string.title_simple_calculator),
            modifier = Modifier
                .padding(horizontal = 16.dp, vertical = 16.dp),
            style = MaterialTheme.typography.headlineMedium
        )
        NumberField(
            value = firstNumber,
            onValueChange = {input ->
                if (input.all { it.isDigit() || it == '.' } && input.count { it == '.' } <= 1) {
                    firstNumber = input
                }
            },
            label = R.string.first_number,
            modifier = Modifier
                .fillMaxWidth()
                .padding(vertical = 16.dp)
        )
        NumberField(
            label = R.string.second_number,
            value = secondNumber,
            onValueChange = {input ->
                if (input.all { it.isDigit() || it == '.' } && input.count { it == '.' } <= 1) {
                    secondNumber = input
                }
            },
            modifier = Modifier
                .fillMaxWidth()
                .padding(vertical = 16.dp)
        )
        OperatorButtons(
            onClick = onButtonClick,
            modifier = Modifier
                .fillMaxWidth()
                .padding(vertical = 16.dp)
        )
        Row(
            modifier = Modifier
                .fillMaxWidth()
                .padding(vertical = 16.dp),
            horizontalArrangement = Arrangement.SpaceBetween
        ) {
            Text(
                text = stringResource(R.string.result_text),
            )
            Text(
                text = stringResource(R.string.result_number_text, result),
            )
        }
    }
}

@Composable
fun NumberField(
    value: String,
    onValueChange: (String) -> Unit,
    @StringRes label: Int,
    modifier: Modifier = Modifier
) {
    TextField(
        value = value,
        onValueChange = onValueChange,
        label = { Text(stringResource(label)) },
        singleLine = true,
        keyboardOptions = KeyboardOptions.Default.copy(
            keyboardType = KeyboardType.Number,
            imeAction = ImeAction.Done
        ),
        modifier = modifier
    )
}

@Composable
fun OperatorButtons(
    onClick: (String) -> Unit,
    modifier: Modifier = Modifier
) {
    Row(
        modifier = modifier,
        horizontalArrangement = Arrangement.SpaceBetween
    ) {
        Button(
            onClick = { onClick("+") },
        ) {
            Text(text = stringResource(R.string.op_plus))
        }
        Button(
            onClick = { onClick("-") },
        ) {
            Text(text = stringResource(R.string.op_minus))
        }
        Button(
            onClick = { onClick("*") },
        ) {
            Text(text = stringResource(R.string.op_multiply))
        }
        Button(
            onClick = { onClick("/") },
        ) {
            Text(text = stringResource(R.string.op_divide))
        }
    }
}

private fun calculateResult(firstNumber: String, secondNumber: String, operator: String): String {
    if (firstNumber.isEmpty() || secondNumber.isEmpty()) {
        return "Please input both numbers"
    }

    val num1 = firstNumber.toDouble()
    val num2 = secondNumber.toDouble()

    val result = when(operator) {
        "+" -> num1 + num2
        "-" -> num1 - num2
        "*" -> num1 * num2
        "/" -> {
            if (num2 != 0.0) {
                num1 / num2
            } else {
                return "Cannot divide by zero"
            }
        }
        else -> return "Invalid operator"
    }

    return NumberFormat.getNumberInstance().format(result)
}

@Preview(showBackground = true)
@Composable
fun CalculatorPreview() {
    CalculatorTheme {
        CalculatorLayout()
    }
}

strings.xml

<resources>
    <string name="app_name">Calculator</string>
    <string name="title_simple_calculator">Simple Calculator</string>
    <string name="result_text">"Result: "</string>
    <string name="first_number">First Number</string>
    <string name="second_number">Second Number</string>
    <string name="result_number_text">%s</string>
    <string name="op_plus">\u002b</string>
    <string name="op_minus">\u2212</string>
    <string name="op_multiply">\u00d7</string>
    <string name="op_divide">\u00f7</string>
</resources>

Screenshot Hasil dan Demo

Screenshot:

Demo: