feat: добавил калькулятор на Jetpack Compose с Material 3

Реализовал Android-приложение с ViewModel, базовой арифметикой и обработкой деления на ноль.

app/build.gradle.kts

@@ -0,0 +1,72 @@
+plugins {
+    id("com.android.application")
+    id("org.jetbrains.kotlin.android")
+    id("org.jetbrains.kotlin.plugin.compose")
+}
+
+android {
+    namespace = "com.heller.calculator"
+    compileSdk = 34
+
+    defaultConfig {
+        applicationId = "com.heller.calculator"
+        minSdk = 24
+        targetSdk = 34
+        versionCode = 1
+        versionName = "1.0"
+
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        vectorDrawables {
+            useSupportLibrary = true
+        }
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = false
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro"
+            )
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    kotlinOptions {
+        jvmTarget = "17"
+    }
+
+    buildFeatures {
+        compose = true
+    }
+
+    packaging {
+        resources {
+            excludes += "/META-INF/{AL2.0,LGPL2.1}"
+        }
+    }
+}
+
+dependencies {
+    val composeBom = platform("androidx.compose:compose-bom:2024.10.00")
+
+    implementation("androidx.core:core-ktx:1.13.1")
+    implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.8.6")
+    implementation("androidx.activity:activity-compose:1.9.3")
+    implementation("androidx.lifecycle:lifecycle-viewmodel-compose:2.8.6")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.8.1")
+
+    implementation(composeBom)
+    implementation("androidx.compose.ui:ui")
+    implementation("androidx.compose.ui:ui-graphics")
+    implementation("androidx.compose.ui:ui-tooling-preview")
+    implementation("androidx.compose.material3:material3")
+    implementation("androidx.compose.material:material-icons-extended")
+
+    debugImplementation("androidx.compose.ui:ui-tooling")
+    debugImplementation("androidx.compose.ui:ui-test-manifest")
+}

app/proguard-rules.pro

@@ -0,0 +1,3 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.kts.

app/src/main/AndroidManifest.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <application
+        android:allowBackup="true"
+        android:icon="@drawable/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@drawable/ic_launcher"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.CalculatorCompose">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:theme="@style/Theme.CalculatorCompose">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>

app/src/main/java/com/heller/calculator/CalculatorScreen.kt

@@ -0,0 +1,153 @@
+package com.heller.calculator
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.SnackbarHost
+import androidx.compose.material3.SnackbarHostState
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import com.heller.calculator.ui.components.CalculatorButton
+import com.heller.calculator.ui.components.CalculatorButtonType
+
+@Composable
+fun CalculatorScreen(viewModel: CalculatorViewModel) {
+    val uiState by viewModel.uiState.collectAsState()
+    val snackbarHostState = remember { SnackbarHostState() }
+
+    LaunchedEffect(uiState.error) {
+        uiState.error?.let { message ->
+            snackbarHostState.showSnackbar(message)
+        }
+    }
+
+    Scaffold(
+        snackbarHost = { SnackbarHost(snackbarHostState) },
+    ) { innerPadding ->
+        Surface(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(innerPadding),
+            color = MaterialTheme.colorScheme.background,
+        ) {
+            Column(
+                modifier = Modifier
+                    .fillMaxSize()
+                    .padding(16.dp),
+                verticalArrangement = Arrangement.SpaceBetween,
+            ) {
+                DisplaySection(display = uiState.display)
+                ButtonGrid(viewModel = viewModel)
+            }
+        }
+    }
+}
+
+@Composable
+private fun DisplaySection(display: String) {
+    Column(
+        modifier = Modifier
+            .fillMaxWidth()
+            .padding(vertical = 24.dp),
+        horizontalAlignment = Alignment.End,
+    ) {
+        Text(
+            text = display,
+            style = MaterialTheme.typography.headlineLarge,
+            color = MaterialTheme.colorScheme.onBackground,
+            textAlign = TextAlign.End,
+            maxLines = 1,
+            overflow = TextOverflow.Ellipsis,
+            modifier = Modifier.fillMaxWidth(),
+        )
+    }
+}
+
+@Composable
+private fun ButtonGrid(viewModel: CalculatorViewModel) {
+    val rows = listOf(
+        listOf("C" to CalculatorButtonType.Clear, "÷" to CalculatorButtonType.Operator),
+        listOf("7" to CalculatorButtonType.Digit, "8" to CalculatorButtonType.Digit, "9" to CalculatorButtonType.Digit, "×" to CalculatorButtonType.Operator),
+        listOf("4" to CalculatorButtonType.Digit, "5" to CalculatorButtonType.Digit, "6" to CalculatorButtonType.Digit, "−" to CalculatorButtonType.Operator),
+        listOf("1" to CalculatorButtonType.Digit, "2" to CalculatorButtonType.Digit, "3" to CalculatorButtonType.Digit, "+" to CalculatorButtonType.Operator),
+        listOf("0" to CalculatorButtonType.Digit, "." to CalculatorButtonType.Digit, "=" to CalculatorButtonType.Equals),
+    )
+
+    Column(
+        verticalArrangement = Arrangement.spacedBy(12.dp),
+    ) {
+        Row(
+            modifier = Modifier.fillMaxWidth(),
+            horizontalArrangement = Arrangement.spacedBy(12.dp),
+        ) {
+            CalculatorButton(
+                label = "C",
+                type = CalculatorButtonType.Clear,
+                onClick = { viewModel.onClear() },
+                modifier = Modifier
+                    .weight(1f)
+                    .aspectRatio(1f),
+            )
+            Spacer(modifier = Modifier.weight(2f))
+            CalculatorButton(
+                label = "÷",
+                type = CalculatorButtonType.Operator,
+                onClick = { viewModel.onOperation(CalculatorOperation.Divide) },
+                modifier = Modifier
+                    .weight(1f)
+                    .aspectRatio(1f),
+            )
+        }
+
+        rows.drop(1).forEach { row ->
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.spacedBy(12.dp),
+            ) {
+                row.forEach { (label, type) ->
+                    val weight = if (label == "0") 2f else 1f
+                    CalculatorButton(
+                        label = label,
+                        type = type,
+                        onClick = { handleButtonClick(label, viewModel) },
+                        modifier = Modifier
+                            .weight(weight)
+                            .aspectRatio(if (label == "0") 2.15f else 1f),
+                    )
+                }
+            }
+        }
+        Spacer(modifier = Modifier.height(8.dp))
+    }
+}
+
+private fun handleButtonClick(label: String, viewModel: CalculatorViewModel) {
+    when (label) {
+        "C" -> viewModel.onClear()
+        "=" -> viewModel.onEquals()
+        "." -> viewModel.onDecimalPoint()
+        "+" -> viewModel.onOperation(CalculatorOperation.Add)
+        "−" -> viewModel.onOperation(CalculatorOperation.Subtract)
+        "×" -> viewModel.onOperation(CalculatorOperation.Multiply)
+        "÷" -> viewModel.onOperation(CalculatorOperation.Divide)
+        else -> label.toIntOrNull()?.let { viewModel.onDigit(it) }
+    }
+}

app/src/main/java/com/heller/calculator/CalculatorState.kt

@@ -0,0 +1,20 @@
+package com.heller.calculator
+
+enum class CalculatorOperation(val symbol: String) {
+    Add("+"),
+    Subtract("-"),
+    Multiply("*"),
+    Divide("/");
+
+    fun apply(a: Double, b: Double): Double = when (this) {
+        Add -> a + b
+        Subtract -> a - b
+        Multiply -> a * b
+        Divide -> a / b
+    }
+}
+
+data class CalculatorUiState(
+    val display: String = "0",
+    val error: String? = null,
+)

app/src/main/java/com/heller/calculator/CalculatorViewModel.kt

@@ -0,0 +1,111 @@
+package com.heller.calculator
+
+import androidx.lifecycle.ViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.update
+import java.math.BigDecimal
+import java.math.RoundingMode
+
+class CalculatorViewModel : ViewModel() {
+
+    private var storedValue: Double? = null
+    private var pendingOperation: CalculatorOperation? = null
+    private var waitingForOperand = false
+
+    private val _uiState = MutableStateFlow(CalculatorUiState())
+    val uiState: StateFlow<CalculatorUiState> = _uiState.asStateFlow()
+
+    fun onDigit(digit: Int) {
+        clearErrorIfNeeded()
+        val current = if (waitingForOperand) {
+            waitingForOperand = false
+            ""
+        } else {
+            val display = _uiState.value.display
+            if (display == "0" && !display.contains(".")) "" else display
+        }
+
+        updateDisplay(current + digit.toString())
+    }
+
+    fun onDecimalPoint() {
+        clearErrorIfNeeded()
+        if (waitingForOperand) {
+            waitingForOperand = false
+            updateDisplay("0.")
+            return
+        }
+        if (!_uiState.value.display.contains(".")) {
+            updateDisplay(_uiState.value.display + ".")
+        }
+    }
+
+    fun onOperation(operation: CalculatorOperation) {
+        clearErrorIfNeeded()
+        val currentValue = _uiState.value.display.toDoubleOrNull() ?: return
+
+        if (storedValue != null && pendingOperation != null && !waitingForOperand) {
+            val result = compute(storedValue!!, pendingOperation!!, currentValue)
+            if (result == null) return
+            storedValue = result
+            updateDisplay(formatResult(result))
+        } else {
+            storedValue = currentValue
+        }
+
+        pendingOperation = operation
+        waitingForOperand = true
+    }
+
+    fun onEquals() {
+        clearErrorIfNeeded()
+        val operation = pendingOperation ?: return
+        val first = storedValue ?: return
+        val second = _uiState.value.display.toDoubleOrNull() ?: return
+
+        val result = compute(first, operation, second) ?: return
+        storedValue = null
+        pendingOperation = null
+        waitingForOperand = true
+        updateDisplay(formatResult(result))
+    }
+
+    fun onClear() {
+        storedValue = null
+        pendingOperation = null
+        waitingForOperand = false
+        _uiState.value = CalculatorUiState()
+    }
+
+    private fun compute(a: Double, operation: CalculatorOperation, b: Double): Double? {
+        if (operation == CalculatorOperation.Divide && b == 0.0) {
+            storedValue = null
+            pendingOperation = null
+            waitingForOperand = false
+            _uiState.value = CalculatorUiState(
+                display = "0",
+                error = "Cannot divide by zero",
+            )
+            return null
+        }
+
+        return operation.apply(a, b)
+    }
+
+    private fun formatResult(value: Double): String {
+        val bd = BigDecimal.valueOf(value).setScale(10, RoundingMode.HALF_UP).stripTrailingZeros()
+        return bd.toPlainString()
+    }
+
+    private fun clearErrorIfNeeded() {
+        _uiState.update { state ->
+            if (state.error != null) state.copy(error = null) else state
+        }
+    }
+
+    private fun updateDisplay(display: String) {
+        _uiState.update { it.copy(display = display) }
+    }
+}

app/src/main/java/com/heller/calculator/MainActivity.kt

@@ -0,0 +1,21 @@
+package com.heller.calculator
+
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.heller.calculator.ui.theme.CalculatorComposeTheme
+
+class MainActivity : ComponentActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
+        setContent {
+            CalculatorComposeTheme {
+                val viewModel: CalculatorViewModel = viewModel()
+                CalculatorScreen(viewModel = viewModel)
+            }
+        }
+    }
+}

app/src/main/java/com/heller/calculator/ui/components/CalculatorButton.kt

@@ -0,0 +1,65 @@
+package com.heller.calculator.ui.components
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.Button
+import androidx.compose.material3.ButtonDefaults
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+
+enum class CalculatorButtonType {
+    Digit,
+    Operator,
+    Equals,
+    Clear,
+}
+
+@Composable
+fun CalculatorButton(
+    label: String,
+    type: CalculatorButtonType,
+    onClick: () -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    val containerColor = when (type) {
+        CalculatorButtonType.Digit -> MaterialTheme.colorScheme.surfaceVariant
+        CalculatorButtonType.Operator -> MaterialTheme.colorScheme.primaryContainer
+        CalculatorButtonType.Equals -> MaterialTheme.colorScheme.primary
+        CalculatorButtonType.Clear -> MaterialTheme.colorScheme.errorContainer
+    }
+
+    val contentColor = when (type) {
+        CalculatorButtonType.Digit -> MaterialTheme.colorScheme.onSurfaceVariant
+        CalculatorButtonType.Operator -> MaterialTheme.colorScheme.onPrimaryContainer
+        CalculatorButtonType.Equals -> MaterialTheme.colorScheme.onPrimary
+        CalculatorButtonType.Clear -> MaterialTheme.colorScheme.onErrorContainer
+    }
+
+    Button(
+        onClick = onClick,
+        modifier = modifier,
+        shape = RoundedCornerShape(24.dp),
+        colors = ButtonDefaults.buttonColors(
+            containerColor = containerColor,
+            contentColor = contentColor,
+        ),
+        elevation = ButtonDefaults.buttonElevation(defaultElevation = 2.dp),
+    ) {
+        Box(
+            modifier = Modifier.fillMaxSize(),
+            contentAlignment = Alignment.Center,
+        ) {
+            Text(
+                text = label,
+                fontSize = 24.sp,
+                style = MaterialTheme.typography.bodyLarge,
+            )
+        }
+    }
+}

app/src/main/java/com/heller/calculator/ui/theme/Color.kt

@@ -0,0 +1,11 @@
+package com.heller.calculator.ui.theme
+
+import androidx.compose.ui.graphics.Color
+
+val Purple80 = Color(0xFFD0BCFF)
+val PurpleGrey80 = Color(0xFFCCC2DC)
+val Pink80 = Color(0xFFEFB8C8)
+
+val Purple40 = Color(0xFF6750A4)
+val PurpleGrey40 = Color(0xFF625B71)
+val Pink40 = Color(0xFF7D5260)

app/src/main/java/com/heller/calculator/ui/theme/Theme.kt

@@ -0,0 +1,60 @@
+package com.heller.calculator.ui.theme
+
+import android.app.Activity
+import android.os.Build
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.darkColorScheme
+import androidx.compose.material3.dynamicDarkColorScheme
+import androidx.compose.material3.dynamicLightColorScheme
+import androidx.compose.material3.lightColorScheme
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.SideEffect
+import androidx.compose.ui.graphics.toArgb
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalView
+import androidx.core.view.WindowCompat
+
+private val DarkColorScheme = darkColorScheme(
+    primary = Purple80,
+    secondary = PurpleGrey80,
+    tertiary = Pink80,
+)
+
+private val LightColorScheme = lightColorScheme(
+    primary = Purple40,
+    secondary = PurpleGrey40,
+    tertiary = Pink40,
+)
+
+@Composable
+fun CalculatorComposeTheme(
+    darkTheme: Boolean = isSystemInDarkTheme(),
+    dynamicColor: Boolean = true,
+    content: @Composable () -> Unit,
+) {
+    val colorScheme = when {
+        dynamicColor && Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
+            val context = LocalContext.current
+            if (darkTheme) dynamicDarkColorScheme(context) else dynamicLightColorScheme(context)
+        }
+
+        darkTheme -> DarkColorScheme
+        else -> LightColorScheme
+    }
+
+    val view = LocalView.current
+    if (!view.isInEditMode) {
+        SideEffect {
+            val window = (view.context as Activity).window
+            window.statusBarColor = colorScheme.surface.toArgb()
+            WindowCompat.getInsetsController(window, view).isAppearanceLightStatusBars = !darkTheme
+        }
+    }
+
+    MaterialTheme(
+        colorScheme = colorScheme,
+        typography = Typography,
+        content = content,
+    )
+}

app/src/main/java/com/heller/calculator/ui/theme/Type.kt

@@ -0,0 +1,24 @@
+package com.heller.calculator.ui.theme
+
+import androidx.compose.material3.Typography
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.sp
+
+val Typography = Typography(
+    bodyLarge = TextStyle(
+        fontFamily = FontFamily.Default,
+        fontWeight = FontWeight.Normal,
+        fontSize = 16.sp,
+        lineHeight = 24.sp,
+        letterSpacing = 0.5.sp,
+    ),
+    headlineLarge = TextStyle(
+        fontFamily = FontFamily.Default,
+        fontWeight = FontWeight.Light,
+        fontSize = 48.sp,
+        lineHeight = 56.sp,
+        letterSpacing = 0.sp,
+    ),
+)

app/src/main/res/drawable/ic_launcher.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="48dp"
+    android:height="48dp"
+    android:viewportWidth="48"
+    android:viewportHeight="48">
+    <path
+        android:fillColor="#6750A4"
+        android:pathData="M0,0h48v48h-48z" />
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M14,12h6v24h-6zM28,12h6v24h-6zM14,22h20v4h-20z" />
+</vector>

app/src/main/res/drawable/ic_launcher_foreground.xml

@@ -0,0 +1,12 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillColor="#6750A4"
+        android:pathData="M0,0h108v108h-108z" />
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M32,28h12v52h-12zM64,28h12v52h-12zM32,48h44v12h-44z" />
+</vector>

app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

app/src/main/res/values/colors.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="ic_launcher_background">#6750A4</color>
+</resources>

app/src/main/res/values/strings.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">Calculator</string>
+</resources>

app/src/main/res/values/themes.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <style name="Theme.CalculatorCompose" parent="android:Theme.Material.Light.NoActionBar" />
+</resources>