基本 DSL 食譜

本食譜提供基本範例，說明如何搭配使用 Navigation 3 API 和兩個畫面，並使用 entryProvider DSL 和持續性返回堆疊。

運作方式

這個範例與基本食譜類似，但有幾項主要差異：

  1. 持續性返回堆疊：使用 rememberNavBackStack(RouteA) 建立及記憶返回堆疊。這樣一來，返回堆疊在設定變更 (例如螢幕旋轉) 時就會保持不變。如要使用 rememberNavBackStack，導覽鍵必須可序列化，因此 RouteA 和 RouteB 會使用 @Serializable 註解，並實作 NavKey 介面。

  2. entryProvider DSL：這個範例使用 entryProvider DSL 定義每個路徑的內容，而非 when 陳述式。entry<RouteType> 函式用於將路徑型別與可組合內容建立關聯。

導覽邏輯維持不變：如要從 RouteA 導覽至 RouteB，請將 RouteB 例項新增至返回堆疊。

/*
 * 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.basicdsl

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.material3.Button
import androidx.compose.material3.Text
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 BasicDslActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        setEdgeToEdgeConfig()
        super.onCreate(savedInstanceState)
        setContent {
            val backStack = rememberNavBackStack(RouteA)

            NavDisplay(
                backStack = backStack,
                onBack = { backStack.removeLastOrNull() },
                entryProvider = entryProvider {
                    entry<RouteA> {
                        ContentGreen("Welcome to Nav3") {
                            Button(onClick = {
                                backStack.add(RouteB("123"))
                            }) {
                                Text("Click to navigate")
                            }
                        }
                    }
                    entry<RouteB> { key ->
                        ContentBlue("Route id: ${key.id} ")
                    }
                }
            )
        }
    }
}

BasicDslActivity.kt