Implement a navigation system

app/build.gradle.kts

@@ -4,6 +4,7 @@ plugins {
     alias(libs.plugins.android.application)
     alias(libs.plugins.kotlin.android)
     alias(libs.plugins.kotlin.compose)
+    alias(libs.plugins.kotlin.serialization)
 }
 
 android {
@@ -44,21 +45,27 @@ android {
 }
 
 dependencies {
-
     implementation(libs.androidx.core.ktx)
     implementation(libs.androidx.lifecycle.runtime.ktx)
     implementation(libs.androidx.lifecycle.viewmodel)
+    implementation(libs.androidx.lifecycle.viewmodel.compose)
     implementation(libs.androidx.activity.compose)
     implementation(platform(libs.androidx.compose.bom))
     implementation(libs.androidx.ui)
     implementation(libs.androidx.ui.graphics)
     implementation(libs.androidx.ui.tooling.preview)
     implementation(libs.androidx.material3)
+
+    implementation(libs.androidx.navigation3.runtime)
+    implementation(libs.androidx.navigation3.ui)
+
     testImplementation(libs.junit)
+
     androidTestImplementation(libs.androidx.junit)
     androidTestImplementation(libs.androidx.espresso.core)
     androidTestImplementation(platform(libs.androidx.compose.bom))
     androidTestImplementation(libs.androidx.ui.test.junit4)
+
     debugImplementation(libs.androidx.ui.tooling)
     debugImplementation(libs.androidx.ui.test.manifest)
 }

app/src/main/java/org/nsh07/pomodoro/MainActivity.kt

@@ -4,21 +4,36 @@ import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
-import androidx.activity.viewModels
 import org.nsh07.pomodoro.ui.AppScreen
+import org.nsh07.pomodoro.ui.NavItem
+import org.nsh07.pomodoro.ui.Screen
 import org.nsh07.pomodoro.ui.theme.TomatoTheme
-import org.nsh07.pomodoro.ui.viewModel.UiViewModel
 
 class MainActivity : ComponentActivity() {
-    val viewModel: UiViewModel by viewModels<UiViewModel>()
-
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
         setContent {
             TomatoTheme {
-                AppScreen(viewModel)
+                AppScreen()
             }
         }
     }
+
+    companion object {
+        val screens = listOf(
+            NavItem(
+                Screen.Timer,
+                R.drawable.hourglass,
+                R.drawable.hourglass_filled,
+                "Timer"
+            ),
+            NavItem(
+                Screen.Settings,
+                R.drawable.settings,
+                R.drawable.settings_filled,
+                "Settings"
+            )
+        )
+    }
 }

app/src/main/java/org/nsh07/pomodoro/ui/AppScreen.kt

@@ -1,5 +1,6 @@
 package org.nsh07.pomodoro.ui
 
+import androidx.compose.animation.Crossfade
 import androidx.compose.foundation.layout.calculateEndPadding
 import androidx.compose.foundation.layout.calculateStartPadding
 import androidx.compose.foundation.layout.padding
@@ -9,7 +10,6 @@ import androidx.compose.material3.Icon
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.ShortNavigationBar
 import androidx.compose.material3.ShortNavigationBarItem
-import androidx.compose.material3.ShortNavigationBarItemDefaults
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
@@ -22,18 +22,23 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalLayoutDirection
 import androidx.compose.ui.res.painterResource
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import androidx.lifecycle.viewmodel.compose.viewModel
+import androidx.navigation3.runtime.entry
+import androidx.navigation3.runtime.entryProvider
+import androidx.navigation3.runtime.rememberNavBackStack
+import androidx.navigation3.ui.NavDisplay
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.withContext
-import org.nsh07.pomodoro.R
+import org.nsh07.pomodoro.MainActivity.Companion.screens
 import org.nsh07.pomodoro.ui.timerScreen.TimerScreen
 import org.nsh07.pomodoro.ui.viewModel.UiViewModel
 
 @OptIn(ExperimentalMaterial3Api::class, ExperimentalMaterial3ExpressiveApi::class)
 @Composable
 fun AppScreen(
-    viewModel: UiViewModel,
+    modifier: Modifier = Modifier,
-    modifier: Modifier = Modifier
+    viewModel: UiViewModel = viewModel()
 ) {
     val uiState by viewModel.uiState.collectAsStateWithLifecycle()
     val remainingTime by viewModel.time.collectAsStateWithLifecycle()
@@ -50,31 +55,63 @@ fun AppScreen(
 
     val layoutDirection = LocalLayoutDirection.current
 
+    val backStack = rememberNavBackStack<Screen>(Screen.Timer)
+
     Scaffold(
         bottomBar = {
             ShortNavigationBar {
-                ShortNavigationBarItem(
+                screens.forEach {
-                    selected = true,
+                    val selected = backStack.last() == it.route
-                    onClick = { },
+                    ShortNavigationBarItem(
-                    icon = { Icon(painterResource(R.drawable.hourglass_filled), null) },
+                        selected = selected,
-                    label = { Text("Timer") },
+                        onClick = if (it.route != Screen.Timer) {
-                    colors = ShortNavigationBarItemDefaults.colors()
+                            {
-                )
+                                if (backStack.size < 2) backStack.add(it.route)
+                                else backStack[1] = it.route
+                            }
+                        } else {
+                            { if (backStack.size > 1) backStack.removeAt(1) }
+                        },
+                        icon = {
+                            Crossfade (selected) { selected ->
+                                if (selected) Icon(painterResource(it.selectedIcon), null)
+                                else Icon(painterResource(it.unselectedIcon), null)
+                            }
+                        },
+                        label = { Text(it.label) }
+                    )
+                }
             }
         }
     ) { contentPadding ->
-        TimerScreen(
+        NavDisplay(
-            uiState = uiState,
+            backStack = backStack,
-            showBrandTitle = showBrandTitle,
+            onBack = { backStack.removeLastOrNull() },
-            progress = { progress },
+            entryProvider = entryProvider {
-            resetTimer = viewModel::resetTimer,
+                entry<Screen.Timer> {
-            skipTimer = viewModel::skipTimer,
+                    TimerScreen(
-            toggleTimer = viewModel::toggleTimer,
+                        uiState = uiState,
-            modifier = modifier.padding(
+                        showBrandTitle = showBrandTitle,
-                start = contentPadding.calculateStartPadding(layoutDirection),
+                        progress = { progress },
-                end = contentPadding.calculateEndPadding(layoutDirection),
+                        resetTimer = viewModel::resetTimer,
-                bottom = contentPadding.calculateBottomPadding()
+                        skipTimer = viewModel::skipTimer,
-            )
+                        toggleTimer = viewModel::toggleTimer,
+                        modifier = modifier.padding(
+                            start = contentPadding.calculateStartPadding(layoutDirection),
+                            end = contentPadding.calculateEndPadding(layoutDirection),
+                            bottom = contentPadding.calculateBottomPadding()
+                        )
+                    )
+                }
+
+                entry<Screen.Settings> {
+                    Text("Settings")
+                }
+
+                entry<Screen.Stats> {
+                    Text("Stats")
+                }
+            }
         )
     }
 }

app/src/main/java/org/nsh07/pomodoro/ui/Screen.kt

@@ -0,0 +1,23 @@
+package org.nsh07.pomodoro.ui
+
+import androidx.annotation.DrawableRes
+import androidx.navigation3.runtime.NavKey
+import kotlinx.serialization.Serializable
+
+sealed class Screen: NavKey {
+    @Serializable
+    object Timer : Screen()
+    @Serializable
+    object Settings : Screen()
+    @Serializable
+    object Stats : Screen()
+}
+
+data class NavItem(
+    val route: Screen,
+    @param:DrawableRes
+    val unselectedIcon: Int,
+    @param:DrawableRes
+    val selectedIcon: Int,
+    val label: String
+)

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

@@ -1,13 +1,10 @@
 <vector xmlns:android="http://schemas.android.com/apk/res/android"
     android:width="24dp"
     android:height="24dp"
-    android:autoMirrored="true"
     android:tint="#000000"
     android:viewportWidth="960"
     android:viewportHeight="960">
-
     <path
         android:fillColor="@android:color/white"
-        android:pathData="M433,880q-27,0 -46.5,-18T363,818l-9,-66q-13,-5 -24.5,-12T307,725l-62,26q-25,11 -50,2t-39,-32l-47,-82q-14,-23 -8,-49t27,-43l53,-40q-1,-7 -1,-13.5v-27q0,-6.5 1,-13.5l-53,-40q-21,-17 -27,-43t8,-49l47,-82q14,-23 39,-32t50,2l62,26q11,-8 23,-15t24,-12l9,-66q4,-26 23.5,-44t46.5,-18h94q27,0 46.5,18t23.5,44l9,66q13,5 24.5,12t22.5,15l62,-26q25,-11 50,-2t39,32l47,82q14,23 8,49t-27,43l-53,40q1,7 1,13.5v27q0,6.5 -2,13.5l53,40q21,17 27,43t-8,49l-48,82q-14,23 -39,32t-50,-2l-60,-26q-11,8 -23,15t-24,12l-9,66q-4,26 -23.5,44T527,880h-94ZM482,620q58,0 99,-41t41,-99q0,-58 -41,-99t-99,-41q-59,0 -99.5,41T342,480q0,58 40.5,99t99.5,41Z" />
+        android:pathData="M433,880q-27,0 -46.5,-18T363,818l-9,-66q-13,-5 -24.5,-12T307,725l-62,26q-25,11 -50,2t-39,-32l-47,-82q-14,-23 -8,-49t27,-43l53,-40q-1,-7 -1,-13.5v-27q0,-6.5 1,-13.5l-53,-40q-21,-17 -27,-43t8,-49l47,-82q14,-23 39,-32t50,2l62,26q11,-8 23,-15t24,-12l9,-66q4,-26 23.5,-44t46.5,-18h94q27,0 46.5,18t23.5,44l9,66q13,5 24.5,12t22.5,15l62,-26q25,-11 50,-2t39,32l47,82q14,23 8,49t-27,43l-53,40q1,7 1,13.5v27q0,6.5 -2,13.5l53,40q21,17 27,43t-8,49l-48,82q-14,23 -39,32t-50,-2l-60,-26q-11,8 -23,15t-24,12l-9,66q-4,26 -23.5,44T527,880h-94ZM440,800h79l14,-106q31,-8 57.5,-23.5T639,633l99,41 39,-68 -86,-65q5,-14 7,-29.5t2,-31.5q0,-16 -2,-31.5t-7,-29.5l86,-65 -39,-68 -99,42q-22,-23 -48.5,-38.5T533,266l-13,-106h-79l-14,106q-31,8 -57.5,23.5T321,327l-99,-41 -39,68 86,64q-5,15 -7,30t-2,32q0,16 2,31t7,30l-86,65 39,68 99,-42q22,23 48.5,38.5T427,694l13,106ZM482,620q58,0 99,-41t41,-99q0,-58 -41,-99t-99,-41q-59,0 -99.5,41T342,480q0,58 40.5,99t99.5,41ZM480,480Z" />
-
 </vector>

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

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="#000000"
+    android:viewportWidth="960"
+    android:viewportHeight="960">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M433,880q-27,0 -46.5,-18T363,818l-9,-66q-13,-5 -24.5,-12T307,725l-62,26q-25,11 -50,2t-39,-32l-47,-82q-14,-23 -8,-49t27,-43l53,-40q-1,-7 -1,-13.5v-27q0,-6.5 1,-13.5l-53,-40q-21,-17 -27,-43t8,-49l47,-82q14,-23 39,-32t50,2l62,26q11,-8 23,-15t24,-12l9,-66q4,-26 23.5,-44t46.5,-18h94q27,0 46.5,18t23.5,44l9,66q13,5 24.5,12t22.5,15l62,-26q25,-11 50,-2t39,32l47,82q14,23 8,49t-27,43l-53,40q1,7 1,13.5v27q0,6.5 -2,13.5l53,40q21,17 27,43t-8,49l-48,82q-14,23 -39,32t-50,-2l-60,-26q-11,8 -23,15t-24,12l-9,66q-4,26 -23.5,44T527,880h-94ZM482,620q58,0 99,-41t41,-99q0,-58 -41,-99t-99,-41q-59,0 -99.5,41T342,480q0,58 40.5,99t99.5,41Z" />
+</vector>

build.gradle.kts

@@ -3,4 +3,5 @@ plugins {
     alias(libs.plugins.android.application) apply false
     alias(libs.plugins.kotlin.android) apply false
     alias(libs.plugins.kotlin.compose) apply false
+    alias(libs.plugins.kotlin.serialization) apply false
 }

gradle/libs.versions.toml

@@ -7,11 +7,15 @@ junitVersion = "1.2.1"
 espressoCore = "3.6.1"
 lifecycleRuntimeKtx = "2.9.1"
 activityCompose = "1.10.1"
-composeBom = "2025.06.01"
+composeBom = "2025.06.02"
+navigation3Runtime = "1.0.0-alpha05"
 
 [libraries]
 androidx-core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "coreKtx" }
 androidx-lifecycle-viewmodel = { module = "androidx.lifecycle:lifecycle-viewmodel", version.ref = "lifecycleRuntimeKtx" }
+androidx-lifecycle-viewmodel-compose = { module = "androidx.lifecycle:lifecycle-viewmodel-compose", version.ref = "lifecycleRuntimeKtx" }
+androidx-navigation3-runtime = { module = "androidx.navigation3:navigation3-runtime", version.ref = "navigation3Runtime" }
+androidx-navigation3-ui = { module = "androidx.navigation3:navigation3-ui", version.ref = "navigation3Runtime" }
 junit = { group = "junit", name = "junit", version.ref = "junit" }
 androidx-junit = { group = "androidx.test.ext", name = "junit", version.ref = "junitVersion" }
 androidx-espresso-core = { group = "androidx.test.espresso", name = "espresso-core", version.ref = "espressoCore" }
@@ -30,4 +34,4 @@ androidx-material3 = { group = "androidx.compose.material3", name = "material3"
 android-application = { id = "com.android.application", version.ref = "agp" }
 kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
 kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }
-
+kotlin-serialization = { id = "org.jetbrains.kotlin.plugin.serialization", version.ref = "kotlin"}