Rezept für die Ansicht am unteren Rand

In diesem Rezept wird gezeigt, wie Sie ein Ziel als modales Bottom Sheet anzeigen.

Funktionsweise

Damit ein Ziel als Bottom Sheet angezeigt wird, müssen Sie zwei Dinge tun:

  1. BottomSheetSceneStrategy verwenden: Erstellen Sie eine Instanz von BottomSheetSceneStrategy und übergeben Sie sie an den Parameter sceneStrategy des Composables NavDisplay.

  2. Metadaten zum Ziel hinzufügen: Fügen Sie den Metadaten des Ziels, das als Bottom Sheet angezeigt werden soll, BottomSheetSceneStrategy.bottomSheet() hinzu. Dies geschieht in der Funktion entry.

In diesem Beispiel ist RouteB als Bottom Sheet konfiguriert. Wenn Sie von RouteA zu RouteB wechseln, wird RouteB in einem modalen Bottom Sheet angezeigt, das vom unteren Bildschirmrand nach oben geschoben wird.

Die Inhalte des Bottom Sheet können nach Bedarf formatiert werden. In diesem Rezept werden die Inhalte so zugeschnitten, dass sie abgerundete Ecken haben.

Weitere Informationen finden Sie in der offiziellen Dokumentation zu benutzerdefinierten Layouts.

/*
 * 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.lifecycle.compose.dropUnlessResumed
import androidx.navigation3.runtime.NavKey
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

@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() },
                sceneStrategies = listOf(bottomSheetStrategy),
                entryProvider = entryProvider {
                    entry<RouteA> {
                        ContentGreen("Welcome to Nav3") {
                            Button(onClick = dropUnlessResumed {
                                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)
                            )
                        )
                    }
                }
            )
        }
    }
}

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.compose.runtime.CompositionLocalProvider
import androidx.lifecycle.compose.LocalLifecycleOwner
import androidx.lifecycle.compose.rememberLifecycleOwner
import androidx.navigation3.runtime.NavEntry
import androidx.navigation3.runtime.NavMetadataKey
import androidx.navigation3.runtime.get
import androidx.navigation3.runtime.metadata
import androidx.navigation3.scene.OverlayScene
import androidx.navigation3.scene.Scene
import androidx.navigation3.scene.SceneStrategy
import androidx.navigation3.scene.SceneStrategyScope
import com.example.nav3recipes.bottomsheet.BottomSheetSceneStrategy.Companion.bottomSheet

/** An [OverlayScene] that renders an [entry] within a [ModalBottomSheet]. */
@OptIn(ExperimentalMaterial3Api::class)
internal data 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: () -> Unit,
) : OverlayScene<T> {

    override val entries: List<NavEntry<T>> = listOf(entry)

    override val content: @Composable (() -> Unit) = {
        val lifecycleOwner = rememberLifecycleOwner()
        ModalBottomSheet(
            onDismissRequest = onBack,
            properties = modalBottomSheetProperties,
        ) {
            CompositionLocalProvider(LocalLifecycleOwner provides lifecycleOwner) {
                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> {

    override fun SceneStrategyScope<T>.calculateScene(entries: List<NavEntry<T>>): Scene<T>? {
        val lastEntry = entries.lastOrNull() ?: return null
        val bottomSheetProperties = lastEntry.metadata[BottomSheetKey] ?: return null
        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].
         */
        fun bottomSheet(modalBottomSheetProperties: ModalBottomSheetProperties = ModalBottomSheetProperties()) =
            metadata {
                put(BottomSheetKey, modalBottomSheetProperties)
            }

        object BottomSheetKey : NavMetadataKey<ModalBottomSheetProperties>
    }

}