NavigatorState.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.navigation
import android.os.Bundle
import androidx.annotation.RestrictTo
import androidx.navigation.NavigatorState.OnTransitionCompleteListener
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.asStateFlow
import java.util.concurrent.locks.ReentrantLock
import kotlin.concurrent.withLock
/**
* The NavigatorState encapsulates the state shared between the [Navigator] and the
* [NavController].
*/
public abstract class NavigatorState {
private val backStackLock = ReentrantLock(true)
private val _backStack: MutableStateFlow<List<NavBackStackEntry>> = MutableStateFlow(listOf())
private val _transitionsInProgress:
MutableStateFlow<Map<NavBackStackEntry, OnTransitionCompleteListener>> =
MutableStateFlow(mapOf())
/**
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public var isNavigating = false
/**
* While the [NavController] is responsible for the combined back stack across all
* Navigators, this back stack is specifically the set of destinations associated
* with this Navigator.
*
* Changing the back stack must be done via [push] and [pop].
*/
public val backStack: StateFlow<List<NavBackStackEntry>> = _backStack.asStateFlow()
/**
* This is the map of currently running transitions to their individual
* [OnTransitionCompleteListener]s. Use this map to retrieve the listener and execute the
* callback once the transition is complete.
*/
public val transitionsInProgress:
StateFlow<Map<NavBackStackEntry, OnTransitionCompleteListener>> =
_transitionsInProgress.asStateFlow()
/**
* Adds the given [backStackEntry] to the [backStack].
*/
public open fun push(backStackEntry: NavBackStackEntry) {
backStackLock.withLock {
_backStack.value = _backStack.value + backStackEntry
}
}
/**
* Provides listener that once activated, adds the given [backStackEntry] to the [backStack].
*/
public open fun pushWithTransition(
backStackEntry: NavBackStackEntry
): OnTransitionCompleteListener {
push(backStackEntry)
return OnTransitionCompleteListener {
removeInProgressTransition(backStackEntry)
}
}
/**
* Create a new [NavBackStackEntry] from a given [destination] and [arguments].
*/
public abstract fun createBackStackEntry(
destination: NavDestination,
arguments: Bundle?
): NavBackStackEntry
/**
* Pop all destinations up to and including [popUpTo]. This will remove those
* destinations from the [backStack], saving their state if [saveState] is `true`.
*/
public open fun pop(popUpTo: NavBackStackEntry, saveState: Boolean) {
backStackLock.withLock {
_backStack.value = _backStack.value.takeWhile { it != popUpTo }
}
}
/**
* Provides listener that once activated, Pops all destinations up to and including [popUpTo].
*
* This will remove those destinations from the [backStack], saving their state if
* [saveState] is `true`.
*/
public open fun popWithTransition(
popUpTo: NavBackStackEntry,
saveState: Boolean
): OnTransitionCompleteListener {
val listener = OnTransitionCompleteListener {
removeInProgressTransition(popUpTo)
}
pop(popUpTo, saveState)
return listener
}
/**
* Adds a transition listener to the group of in progress transitions.
*
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public fun addInProgressTransition(
entry: NavBackStackEntry,
listener: OnTransitionCompleteListener
) {
_transitionsInProgress.value = _transitionsInProgress.value + (entry to listener)
}
/**
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public fun removeInProgressTransition(entry: NavBackStackEntry) {
_transitionsInProgress.value = _transitionsInProgress.value - entry
}
/**
* OnTransitionCompleteListener receives a callback when a destination transition is complete.
*/
public fun interface OnTransitionCompleteListener {
/**
* Callback for when the transition has completed.
*/
public fun onTransitionComplete()
}
}