DialogNavigator.kt
/*
* Copyright 2020 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.navigation.compose
import androidx.compose.runtime.Composable
import androidx.compose.runtime.collectAsState
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.saveable.rememberSaveableStateHolder
import androidx.compose.runtime.setValue
import androidx.compose.ui.window.Dialog
import androidx.compose.ui.window.DialogProperties
import androidx.lifecycle.Lifecycle
import androidx.navigation.FloatingWindow
import androidx.navigation.NavBackStackEntry
import androidx.navigation.NavDestination
import androidx.navigation.NavOptions
import androidx.navigation.Navigator
import androidx.navigation.NavigatorState
import androidx.navigation.compose.DialogNavigator.Destination
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
/**
* Navigator that navigates through [Composable]s that will be hosted within a
* [Dialog]. Every destination using this Navigator must set a valid [Composable] by setting it
* directly on an instantiated [Destination] or calling [dialog].
*/
@Navigator.Name("dialog")
public class DialogNavigator : Navigator<Destination>() {
private var attached by mutableStateOf(false)
/**
* Get the back stack from the [state]. NavHost will compose at least
* once (due to the use of [androidx.compose.runtime.DisposableEffect]) before
* the Navigator is attached, so we specifically return an empty flow if we
* aren't attached yet.
*/
private val backStack: StateFlow<List<NavBackStackEntry>> get() = if (attached) {
state.backStack
} else {
MutableStateFlow(emptyList())
}
/**
* Show each [Destination] on the back stack as a [Dialog].
*
* Note that [NavHost] will call this for you; you do not need to call it manually.
*/
internal val Dialogs: @Composable () -> Unit = @Composable {
val saveableStateHolder = rememberSaveableStateHolder()
val dialogBackStack by backStack.collectAsState()
dialogBackStack.filter { backStackEntry ->
backStackEntry.lifecycle.currentState.isAtLeast(Lifecycle.State.STARTED)
}.forEach { backStackEntry ->
val destination = backStackEntry.destination as Destination
Dialog(
onDismissRequest = { state.pop(backStackEntry, false) },
properties = destination.dialogProperties
) {
// while in the scope of the composable, we provide the navBackStackEntry as the
// ViewModelStoreOwner and LifecycleOwner
backStackEntry.LocalOwnersProvider(saveableStateHolder) {
destination.content(backStackEntry)
}
}
}
}
override fun onAttach(state: NavigatorState) {
super.onAttach(state)
attached = true
}
override fun navigate(
entries: List<NavBackStackEntry>,
navOptions: NavOptions?,
navigatorExtras: Extras?
) {
entries.forEach { entry ->
state.push(entry)
}
}
override fun createDestination(): Destination {
return Destination(this) { }
}
override fun popBackStack(popUpTo: NavBackStackEntry, savedState: Boolean) {
state.pop(popUpTo, savedState)
}
/**
* NavDestination specific to [DialogNavigator]
*/
@NavDestination.ClassType(Composable::class)
public class Destination(
navigator: DialogNavigator,
internal val dialogProperties: DialogProperties = DialogProperties(),
internal val content: @Composable (NavBackStackEntry) -> Unit
) : NavDestination(navigator), FloatingWindow
internal companion object {
internal const val NAME = "dialog"
}
}