Add bottom sheet recipe

app/src/main/AndroidManifest.xml

@@ -65,6 +65,10 @@
             android:name=".dialog.DialogActivity"
             android:exported="true"
             android:theme="@style/Theme.Nav3Recipes"/>
+        <activity
+            android:name=".bottomsheet.BottomSheetActivity"
+            android:exported="true"
+            android:theme="@style/Theme.Nav3Recipes"/>
         <activity
             android:name=".scenes.materiallistdetail.MaterialListDetailActivity"
             android:exported="true"

app/src/main/java/com/example/nav3recipes/bottomsheet/BottomSheetActivity.kt

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.nav3recipes.bottomsheet
+
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.Button
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Text
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.unit.dp
+import androidx.navigation3.runtime.NavKey
+import androidx.navigation3.runtime.entry
+import androidx.navigation3.runtime.entryProvider
+import androidx.navigation3.runtime.rememberNavBackStack
+import androidx.navigation3.ui.NavDisplay
+import com.example.nav3recipes.content.ContentBlue
+import com.example.nav3recipes.content.ContentGreen
+import com.example.nav3recipes.ui.setEdgeToEdgeConfig
+import kotlinx.serialization.Serializable
+
+/**
+ * This recipe demonstrates how to create a bottom sheet. It does this by:
+ *
+ * - Adding the `BottomSheetSceneStrategy` to the list of strategies used by `NavDisplay`.
+ * - Adding `BottomSheetSceneStrategy.bottomsheet` to a `NavEntry`'s metadata to indicate that it
+ * is a bottom sheet. In this case it is applied to the `NavEntry` for `RouteB`.
+ *
+ * See also https://developer.android.com/guide/navigation/navigation-3/custom-layouts
+ */
+
+@Serializable
+private data object RouteA : NavKey
+
+@Serializable
+private data class RouteB(val id: String) : NavKey
+
+class BottomSheetActivity : ComponentActivity() {
+
+    @OptIn(ExperimentalMaterial3Api::class)
+    override fun onCreate(savedInstanceState: Bundle?) {
+        setEdgeToEdgeConfig()
+        super.onCreate(savedInstanceState)
+        setContent {
+            val backStack = rememberNavBackStack(RouteA)
+            val bottomSheetStrategy = remember { BottomSheetSceneStrategy<NavKey>() }
+
+            NavDisplay(
+                backStack = backStack,
+                onBack = { backStack.removeLastOrNull() },
+                sceneStrategy = bottomSheetStrategy,
+                entryProvider = entryProvider {
+                    entry<RouteA> {
+                        ContentGreen("Welcome to Nav3") {
+                            Button(onClick = {
+                                backStack.add(RouteB("123"))
+                            }) {
+                                Text("Click to open bottom sheet")
+                            }
+                        }
+                    }
+                    entry<RouteB>(
+                        metadata = BottomSheetSceneStrategy.bottomSheet()
+                    ) { key ->
+                        ContentBlue(
+                            title = "Route id: ${key.id}",
+                            modifier = Modifier.clip(
+                                shape = RoundedCornerShape(16.dp)
+                            )
+                        )
+                    }
+                }
+            )
+        }
+    }
+}

app/src/main/java/com/example/nav3recipes/bottomsheet/BottomSheetSceneStrategy.kt

@@ -0,0 +1,79 @@
+package com.example.nav3recipes.bottomsheet
+
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.ModalBottomSheet
+import androidx.compose.material3.ModalBottomSheetProperties
+import androidx.compose.runtime.Composable
+import androidx.navigation3.runtime.NavEntry
+import androidx.navigation3.ui.OverlayScene
+import androidx.navigation3.ui.Scene
+import androidx.navigation3.ui.SceneStrategy
+
+/** An [OverlayScene] that renders an [entry] within a [ModalBottomSheet]. */
+@OptIn(ExperimentalMaterial3Api::class)
+internal class BottomSheetScene<T : Any>(
+    override val key: T,
+    override val previousEntries: List<NavEntry<T>>,
+    override val overlaidEntries: List<NavEntry<T>>,
+    private val entry: NavEntry<T>,
+    private val modalBottomSheetProperties: ModalBottomSheetProperties,
+    private val onBack: (count: Int) -> Unit,
+) : OverlayScene<T> {
+
+    override val entries: List<NavEntry<T>> = listOf(entry)
+
+    override val content: @Composable (() -> Unit) = {
+        ModalBottomSheet(
+            onDismissRequest = { onBack(1) },
+            properties = modalBottomSheetProperties,
+        ) {
+            entry.Content()
+        }
+    }
+}
+
+/**
+ * A [SceneStrategy] that displays entries that have added [bottomSheet] to their [NavEntry.metadata]
+ * within a [ModalBottomSheet] instance.
+ *
+ * This strategy should always be added before any non-overlay scene strategies.
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+class BottomSheetSceneStrategy<T : Any>() : SceneStrategy<T> {
+
+    @Composable
+    override fun calculateScene(
+        entries: List<NavEntry<T>>,
+        onBack: (Int) -> Unit
+    ): Scene<T>? {
+        val lastEntry = entries.lastOrNull()
+        val bottomSheetProperties = lastEntry?.metadata?.get(BOTTOM_SHEET_KEY) as? ModalBottomSheetProperties
+        return bottomSheetProperties?.let { properties ->
+            @Suppress("UNCHECKED_CAST")
+            BottomSheetScene(
+                key = lastEntry.contentKey as T,
+                previousEntries = entries.dropLast(1),
+                overlaidEntries = entries.dropLast(1),
+                entry = lastEntry,
+                modalBottomSheetProperties = properties,
+                onBack = onBack
+            )
+        }
+    }
+
+    companion object {
+        /**
+         * Function to be called on the [NavEntry.metadata] to mark this entry as something that
+         * should be displayed within a [ModalBottomSheet].
+         *
+         * @param modalBottomSheetProperties properties that should be passed to the containing
+         * [ModalBottomSheet].
+         */
+        @OptIn(ExperimentalMaterial3Api::class)
+        fun bottomSheet(
+            modalBottomSheetProperties: ModalBottomSheetProperties = ModalBottomSheetProperties()
+        ): Map<String, Any> = mapOf(BOTTOM_SHEET_KEY to modalBottomSheetProperties)
+
+        internal const val BOTTOM_SHEET_KEY = "bottomsheet"
+    }
+}