/*
* 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.activity.compose.LocalOnBackPressedDispatcherOwner
import androidx.compose.foundation.layout.Box
import androidx.compose.runtime.Composable
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.collectAsState
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.setValue
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.Lifecycle
import androidx.lifecycle.LifecycleEventObserver
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.SwipeToDismissValue
import androidx.wear.compose.material.SwipeToDismissBox
import androidx.wear.compose.material.SwipeToDismissBoxState
import androidx.wear.compose.material.SwipeToDismissKeys
import androidx.wear.compose.material.edgeSwipeToDismiss
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.
*
* Example of a [SwipeDismissableNavHost] alternating between 2 screens:
* @sample androidx.wear.compose.navigation.samples.SimpleNavHost
*
* Example of a [SwipeDismissableNavHost] for which a destination has a named argument:
* @sample androidx.wear.compose.navigation.samples.NavHostWithNamedArgument
*
* @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 state State containing information about ongoing swipe and animation.
* @param route The route for the graph
* @param builder The builder used to construct the graph
*/
@Composable
public fun SwipeDismissableNavHost(
navController: NavHostController,
startDestination: String,
modifier: Modifier = Modifier,
state: SwipeDismissableNavHostState = rememberSwipeDismissableNavHostState(),
route: String? = null,
builder: NavGraphBuilder.() -> Unit
) =
SwipeDismissableNavHost(
navController,
remember(route, startDestination, builder) {
navController.createGraph(startDestination, route, builder)
},
modifier,
state = state,
)
/**
* 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.
*
* Example of a [SwipeDismissableNavHost] alternating between 2 screens:
* @sample androidx.wear.compose.navigation.samples.SimpleNavHost
*
* Example of a [SwipeDismissableNavHost] for which a destination has a named argument:
* @sample androidx.wear.compose.navigation.samples.NavHostWithNamedArgument
*
* @param navController [NavHostController] for this host
* @param graph Graph for this host
* @param modifier [Modifier] to be applied to the layout
* @param state State containing information about ongoing swipe and animation.
*
* @throws IllegalArgumentException if no WearNavigation.Destination is on the navigation backstack.
*/
@Composable
public fun SwipeDismissableNavHost(
navController: NavHostController,
graph: NavGraph,
modifier: Modifier = Modifier,
state: SwipeDismissableNavHostState = rememberSwipeDismissableNavHostState(),
) {
val lifecycleOwner = LocalLifecycleOwner.current
val viewModelStoreOwner = checkNotNull(LocalViewModelStoreOwner.current) {
"SwipeDismissableNavHost requires a ViewModelStoreOwner to be provided " +
"via LocalViewModelStoreOwner"
}
val onBackPressedDispatcherOwner = LocalOnBackPressedDispatcherOwner.current
val onBackPressedDispatcher = onBackPressedDispatcherOwner?.onBackPressedDispatcher
// Setup the navController with proper owners
navController.setLifecycleOwner(lifecycleOwner)
navController.setViewModelStore(viewModelStoreOwner.viewModelStore)
if (onBackPressedDispatcher != null) {
navController.setOnBackPressedDispatcher(onBackPressedDispatcher)
}
// Ensure that the NavController only receives back events while
// the NavHost is in composition
DisposableEffect(navController) {
navController.enableOnBackPressed(true)
onDispose {
navController.enableOnBackPressed(false)
}
}
// Then set the graph
navController.graph = graph
val stateHolder = rememberSaveableStateHolder()
// Find the WearNavigator, returning early if it isn't found
// (such as is the case when using TestNavHostController).
val wearNavigator = navController.navigatorProvider.get<Navigator<out NavDestination>>(
WearNavigator.NAME
) as? WearNavigator ?: return
val backStack by wearNavigator.backStack.collectAsState()
val transitionsInProgress by wearNavigator.transitionsInProgress.collectAsState()
var initialContent by remember { mutableStateOf(true) }
val previous = if (backStack.size <= 1) null else backStack[backStack.lastIndex - 1]
// Get the current navigation backstack entry. If the backstack is empty, it could be because
// no WearNavigator.Destinations were added to the navigation backstack (be sure to build
// the NavGraph using androidx.wear.compose.navigation.composable) or because the last entry
// was popped prior to navigating (instead, use navigate with popUpTo).
val current = if (backStack.isNotEmpty()) backStack.last() else throw IllegalArgumentException(
"The WearNavigator backstack is empty, there is no navigation destination to display."
)
val swipeState = state.swipeToDismissBoxState
LaunchedEffect(swipeState.currentValue) {
// This effect operates when the swipe gesture is complete:
// 1) Resets the screen offset (otherwise, the next destination is draw off-screen)
// 2) Pops the navigation back stack to return to the previous level
if (swipeState.currentValue == SwipeToDismissValue.Dismissed) {
swipeState.snapTo(SwipeToDismissValue.Default)
navController.popBackStack()
}
}
LaunchedEffect(swipeState.isAnimationRunning) {
// This effect marks the transitions completed when swipe animations finish,
// so that the navigation backstack entries can go to Lifecycle.State.RESUMED.
if (swipeState.isAnimationRunning == false) {
transitionsInProgress.forEach { entry ->
wearNavigator.onTransitionComplete(entry)
}
}
}
SwipeToDismissBox(
state = swipeState,
modifier = Modifier,
hasBackground = previous != null,
backgroundKey = previous?.id ?: SwipeToDismissKeys.Background,
contentKey = current.id,
content = { isBackground ->
BoxedStackEntryContent(if (isBackground) previous else current, stateHolder, modifier)
}
)
DisposableEffect(previous, current) {
if (initialContent) {
// There are no animations for showing the initial content, so mark transitions complete,
// allowing the navigation backstack entry to go to Lifecycle.State.RESUMED.
transitionsInProgress.forEach { entry ->
wearNavigator.onTransitionComplete(entry)
}
initialContent = false
}
onDispose {
transitionsInProgress.forEach { entry ->
wearNavigator.onTransitionComplete(entry)
}
}
}
}
/**
* State for [SwipeDismissableNavHost]
*
* @param swipeToDismissBoxState State for [SwipeToDismissBox], which is used to support the
* swipe-to-dismiss gesture in [SwipeDismissableNavHost] and can also be used to support
* edge-swiping, using [edgeSwipeToDismiss].
*/
public class SwipeDismissableNavHostState(
internal val swipeToDismissBoxState: SwipeToDismissBoxState
)
/**
* Create a [SwipeToDismissBoxState] and remember it.
*
* @param swipeToDismissBoxState State for [SwipeToDismissBox], which is used to support the
* swipe-to-dismiss gesture in [SwipeDismissableNavHost] and can also be used to support
* edge-swiping, using [edgeSwipeToDismiss].
*/
@Composable
public fun rememberSwipeDismissableNavHostState(
swipeToDismissBoxState: SwipeToDismissBoxState = rememberSwipeToDismissBoxState(),
): SwipeDismissableNavHostState {
return remember(swipeToDismissBoxState) {
SwipeDismissableNavHostState(swipeToDismissBoxState)
}
}
@Composable
private fun BoxedStackEntryContent(
entry: NavBackStackEntry?,
saveableStateHolder: SaveableStateHolder,
modifier: Modifier = Modifier,
) {
if (entry != null) {
var lifecycleState by remember {
mutableStateOf(entry.lifecycle.currentState)
}
DisposableEffect(entry.lifecycle) {
val observer = LifecycleEventObserver { _, event ->
lifecycleState = event.targetState
}
entry.lifecycle.addObserver(observer)
onDispose {
entry.lifecycle.removeObserver(observer)
}
}
if (lifecycleState.isAtLeast(Lifecycle.State.CREATED)) {
Box(modifier, propagateMinConstraints = true) {
val destination = entry.destination as WearNavigator.Destination
entry.LocalOwnersProvider(saveableStateHolder) {
destination.content(entry)
}
}
}
}
}