Don Turner
2 months ago
parent
adcc3871be
commit
c9bba49957
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/*
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* Copyright 2025 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.samples.apps.nowinandroid.core.navigation.simple
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import androidx.compose.runtime.Composable
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import androidx.compose.runtime.MutableState
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import androidx.compose.runtime.getValue
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import androidx.compose.runtime.mutableStateOf
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import androidx.compose.runtime.remember
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import androidx.compose.runtime.saveable.rememberSerializable
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import androidx.compose.runtime.setValue
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import androidx.compose.runtime.snapshots.SnapshotStateList
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import androidx.compose.runtime.toMutableStateList
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import androidx.navigation3.runtime.NavBackStack
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import androidx.navigation3.runtime.NavEntry
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import androidx.navigation3.runtime.NavKey
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import androidx.navigation3.runtime.rememberDecoratedNavEntries
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import androidx.navigation3.runtime.rememberNavBackStack
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import androidx.navigation3.runtime.rememberSaveableStateHolderNavEntryDecorator
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import androidx.navigation3.runtime.serialization.NavKeySerializer
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import androidx.savedstate.compose.serialization.serializers.MutableStateSerializer
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/**
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* Create a navigation state that persists config changes and process death.
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*/
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@Composable
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fun rememberNavigationState(
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startRoute: NavKey,
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topLevelRoutes: Set<NavKey>
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): NavigationState {
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val topLevelRoute = rememberSerializable(
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startRoute, topLevelRoutes,
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serializer = MutableStateSerializer(NavKeySerializer())
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) {
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mutableStateOf(startRoute)
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}
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val backStacks = topLevelRoutes.associateWith { key -> rememberNavBackStack(key) }
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return remember(startRoute, topLevelRoutes) {
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NavigationState(
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startRoute = startRoute,
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topLevelRoute = topLevelRoute,
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backStacks = backStacks
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)
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}
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}
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/**
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* State holder for navigation state.
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*
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* @param startRoute - the start route. The user will exit the app through this route.
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* @param topLevelRoute - the current top level route
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* @param backStacks - the back stacks for each top level route
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*/
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class NavigationState(
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val startRoute: NavKey,
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topLevelRoute: MutableState<NavKey>,
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val backStacks: Map<NavKey, NavBackStack<NavKey>>
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) {
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var topLevelRoute: NavKey by topLevelRoute
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val stacksInUse: List<NavKey>
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get() = if (topLevelRoute == startRoute) {
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listOf(startRoute)
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} else {
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listOf(startRoute, topLevelRoute)
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}
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}
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/**
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* Convert NavigationState into NavEntries.
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*/
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@Composable
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fun NavigationState.toEntries(
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entryProvider: (NavKey) -> NavEntry<NavKey>
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): SnapshotStateList<NavEntry<NavKey>> {
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val decoratedEntries = backStacks.mapValues { (_, stack) ->
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val decorators = listOf(
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rememberSaveableStateHolderNavEntryDecorator<NavKey>(),
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)
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rememberDecoratedNavEntries(
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backStack = stack,
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entryDecorators = decorators,
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entryProvider = entryProvider
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)
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}
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return stacksInUse
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.flatMap { decoratedEntries[it] ?: emptyList() }
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.toMutableStateList()
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}
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@ -0,0 +1,47 @@
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/*
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* Copyright 2025 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.nav3recipes.multiplestacks
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import androidx.navigation3.runtime.NavKey
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import com.google.samples.apps.nowinandroid.core.navigation.simple.NavigationState
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/**
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* Handles navigation events (forward and back) by updating the navigation state.
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*/
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class Navigator(val state: NavigationState){
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fun navigate(route: NavKey){
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if (route in state.backStacks.keys){
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// This is a top level route, just switch to it
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state.topLevelRoute = route
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} else {
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state.backStacks[state.topLevelRoute]?.add(route)
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}
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}
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fun goBack(){
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val currentStack = state.backStacks[state.topLevelRoute] ?:
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error("Stack for ${state.topLevelRoute} not found")
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val currentRoute = currentStack.last()
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// If we're at the base of the current route, go back to the start route stack.
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if (currentRoute == state.topLevelRoute){
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state.topLevelRoute = state.startRoute
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} else {
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currentStack.removeLastOrNull()
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}
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}
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}
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