SwipeDismissableNavHost.kt
/*
* Copyright 2021 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 androidx.wear.compose.navigation
import androidx.compose.foundation.layout.Box
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.collectAsState
import androidx.compose.runtime.getValue
import androidx.compose.runtime.remember
import androidx.compose.runtime.saveable.SaveableStateHolder
import androidx.compose.runtime.saveable.rememberSaveableStateHolder
import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.LocalLifecycleOwner
import androidx.lifecycle.viewmodel.compose.LocalViewModelStoreOwner
import androidx.navigation.NavBackStackEntry
import androidx.navigation.NavDestination
import androidx.navigation.NavGraph
import androidx.navigation.NavGraphBuilder
import androidx.navigation.NavHostController
import androidx.navigation.Navigator
import androidx.navigation.createGraph
import androidx.navigation.compose.LocalOwnersProvider
import androidx.navigation.get
import androidx.wear.compose.material.ExperimentalWearMaterialApi
import androidx.wear.compose.material.SwipeDismissTarget
import androidx.wear.compose.material.SwipeToDismissBox
import androidx.wear.compose.material.SwipeToDismissBoxDefaults
import androidx.wear.compose.material.rememberSwipeToDismissBoxState
/**
* Provides a place in the Compose hierarchy for self-contained navigation to occur,
* with backwards navigation provided by a swipe gesture.
*
* Once this is called, any Composable within the given [NavGraphBuilder] can be navigated to from
* the provided [navController].
*
* The builder passed into this method is [remember]ed. This means that for this NavHost, the
* contents of the builder cannot be changed.
*
* Content is displayed within a [SwipeToDismissBox], showing the current navigation level.
* During a swipe-to-dismiss gesture, the previous navigation level (if any) is shown in
* the background. [SwipeToDismissBox] has not yet been integrated with Android's
* default handling for swipe to dismiss on Wear applications - until that is completed,
* android:windowSwipeToDismiss must be disabled for applications using [SwipeDismissableNavHost].
*
* @param navController The navController for this host
* @param startDestination The route for the start destination
* @param modifier The modifier to be applied to the layout
* @param route The route for the graph
* @param builder The builder used to construct the graph
*/
@ExperimentalWearMaterialApi
@Composable
public fun SwipeDismissableNavHost(
navController: NavHostController,
startDestination: String,
modifier: Modifier = Modifier,
route: String? = null,
builder: NavGraphBuilder.() -> Unit
) =
SwipeDismissableNavHost(
navController,
remember(route, startDestination, builder) {
navController.createGraph(startDestination, route, builder)
},
modifier
)
/**
* Provides a place in the Compose hierarchy for self-contained navigation to occur,
* with backwards navigation provided by a swipe gesture.
*
* Once this is called, any Composable within the given [NavGraphBuilder] can be navigated to from
* the provided [navController].
*
* The builder passed into this method is [remember]ed. This means that for this NavHost, the
* contents of the builder cannot be changed.
*
* Content is displayed within a [SwipeToDismissBox], showing the current navigation level.
* During a swipe-to-dismiss gesture, the previous navigation level (if any) is shown in
* the background. [SwipeToDismissBox] has not yet been integrated with Android's
* default handling for swipe to dismiss on Wear applications - until that is completed,
* android:windowSwipeToDismiss must be disabled for applications using [SwipeDismissableNavHost].
*
* @param navController [NavHostController] for this host
* @param graph Graph for this host
* @param modifier [Modifier] to be applied to the layout.
*/
@ExperimentalWearMaterialApi
@Composable
public fun SwipeDismissableNavHost(
navController: NavHostController,
graph: NavGraph,
modifier: Modifier = Modifier
) {
val lifecycleOwner = LocalLifecycleOwner.current
val viewModelStoreOwner = checkNotNull(LocalViewModelStoreOwner.current) {
"NavHost requires a ViewModelStoreOwner to be provided via LocalViewModelStoreOwner"
}
// Setup the navController with proper owners
navController.setLifecycleOwner(lifecycleOwner)
navController.setViewModelStore(viewModelStoreOwner.viewModelStore)
// Then set the graph
navController.graph = graph
val stateHolder = rememberSaveableStateHolder()
// Find the ComposeNavigator, returning early if it isn't found
// (such as is the case when using TestNavHostController)
val composeNavigator = navController.navigatorProvider.get<Navigator<out NavDestination>>(
WearNavigator.NAME
) as? WearNavigator ?: return
val backStack by composeNavigator.backStack.collectAsState()
val previous = if (backStack.size <= 1) null else backStack[backStack.lastIndex - 1]
val current = if (backStack.isEmpty()) null else backStack.last()
val state = rememberSwipeToDismissBoxState()
LaunchedEffect(state.currentValue) {
if (state.currentValue == SwipeDismissTarget.Dismissal) {
state.snapTo(SwipeDismissTarget.Original)
navController.popBackStack()
}
}
SwipeToDismissBox(
state = state,
modifier = Modifier,
backgroundKey = previous?.id ?: SwipeToDismissBoxDefaults.BackgroundKey,
contentKey = current?.id ?: SwipeToDismissBoxDefaults.ContentKey,
content = { isBackground ->
BoxedStackEntryContent(if (isBackground) previous else current, stateHolder, modifier)
},
)
}
@Composable
private fun BoxedStackEntryContent(
entry: NavBackStackEntry?,
saveableStateHolder: SaveableStateHolder,
modifier: Modifier = Modifier,
) {
if (entry != null) {
Box(modifier, propagateMinConstraints = true) {
val destination = entry.destination as WearNavigator.Destination
entry.LocalOwnersProvider(saveableStateHolder) {
destination.content(entry)
}
}
}
}