Resep Parcelable Dasar

Resep ini menunjukkan contoh dasar cara membuat tumpukan kembali persisten yang bertahan dari perubahan konfigurasi, tanpa menggunakan kotlinx.serialization. Sebagai gantinya, library ini menggunakan Parcelable Android dan plugin kotlin-parcelize untuk menyimpan dan memulihkan status navigasi.

Cara kerjanya

Dalam contoh ini, RouteA dan RouteB mengimplementasikan antarmuka penanda, Route, yang memperluas Parcelable. Class tersebut juga dianotasi dengan @Parcelize dari plugin kotlin-parcelize, yang otomatis menghasilkan implementasi Parcelable:

sealed interface Route : Parcelable

@Parcelize
data object RouteA : Route

@Parcelize
data class RouteB(val id: String) : Route

Untuk membuat stack kembali persisten, resep ini menentukan fungsi rememberParcelableBackStack. Untuk memastikan bahwa NavDisplay dan composable lainnya mengetahui perubahan pada data sebelumnya, data sebelumnya disimpan dalam SnapshotStateList.

@Composable
fun <T : Parcelable> rememberParcelableBackStack(vararg elements: T): SnapshotStateList<T> {
    return rememberSaveable {
        mutableStateListOf(*elements)
    }
}

Hal ini berfungsi sebagai alternatif untuk rememberNavBackStack bawaan dari androidx.navigation3.runtime yang mengandalkan kotlinx.serialization. Gunakan pendekatan ini jika aplikasi Anda lebih memilih Parcelable dan menghindari bergantung pada kotlinx.serialization.

/*
 * Copyright 2026 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.basicparcelable

import android.os.Bundle
import android.os.Parcelable
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.material3.Button
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableStateListOf
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.snapshots.SnapshotStateList
import androidx.lifecycle.compose.dropUnlessResumed
import androidx.navigation3.runtime.NavEntry
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.parcelize.Parcelize

sealed interface Route : Parcelable

@Parcelize
data object RouteA : Route

@Parcelize
data class RouteB(val id: String) : Route

/**
 * Creates and remembers a [SnapshotStateList] to hold a back stack of [Parcelable] routes
 * that survives configuration changes and process death.
 *
 * @param T The route type, which must implement [Parcelable].
 * @param elements The initial routes to populate the back stack.
 * @return A reactive [SnapshotStateList] managing the navigation back stack.
 */
@Composable
fun <T : Parcelable> rememberParcelableBackStack(vararg elements: T): SnapshotStateList<T> {
    return rememberSaveable {
        mutableStateListOf(*elements)
    }
}

class BasicParcelableActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        setEdgeToEdgeConfig()
        super.onCreate(savedInstanceState)
        setContent {
            val backStack = rememberParcelableBackStack<Route>(RouteA)

            NavDisplay(
                backStack = backStack,
                onBack = { backStack.removeLastOrNull() },
                entryProvider = { key ->
                    when (key) {
                        is RouteA -> NavEntry(key) {
                            ContentGreen("Welcome to Nav3") {
                                Button(onClick = dropUnlessResumed {
                                    backStack.add(RouteB("123"))
                                }) {
                                    Text("Click to navigate")
                                }
                            }
                        }

                        is RouteB -> NavEntry(key) {
                            ContentBlue("Route id: ${key.id} ")
                        }
                    }
                }
            )
        }
    }
}