NavBackStack

Artifact: androidx.navigation3:navigation3-runtime

Added in 1.0.0

Kotlin |Java

Cmn

@Serializable
class NavBackStack<T : NavKey> : MutableList, StateObject

A mutable back stack of NavKey elements that integrates with Compose state.

This class wraps a SnapshotStateList so that updates to the stack automatically trigger recomposition in any observing Composables. It also implements StateObject, which allows it to participate in Compose's snapshot system directly.

Typically, you won’t construct a NavBackStack manually. Instead, prefer using rememberNavBackStack, which provides a stack that is automatically saved and restored across process death and configuration changes.

Example

val backStack = NavBackStack(Home("start"))
backStack += Details("item42") // pushes onto stack
backStack.removeLast()         // pops stack

import androidx.compose.runtime.saveable.rememberSerializable
import androidx.navigation3.runtime.NavBackStack
import androidx.navigation3.runtime.NavKey
import androidx.navigation3.runtime.samples.NavBackStackSamples.Chat
import androidx.navigation3.runtime.samples.NavBackStackSamples.Home
import androidx.navigation3.runtime.samples.NavBackStackSamples.Spaces
import androidx.savedstate.serialization.SavedStateConfiguration

// https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/polymorphism.md#open-polymorphism
rememberSerializable(
    serializer = serializer(),
    configuration =
        SavedStateConfiguration {
            serializersModule = SerializersModule {
                polymorphic(baseClass = NavKey::class) {
                    subclass(clazz = Home::class)
                    subclass(clazz = Chat::class)
                    subclass(clazz = Spaces::class)
                }
            }
        },
) {
    NavBackStack<NavKey>()
}

import androidx.compose.runtime.saveable.rememberSerializable
import androidx.navigation3.runtime.NavBackStack
import androidx.navigation3.runtime.samples.NavBackStackSamples.SealedKey

// https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/polymorphism.md#closed-polymorphism
rememberSerializable(serializer = serializer()) { NavBackStack<SealedKey>() }

See also
`rememberNavBackStack`	for lifecycle-aware persistence.

Summary

Public constructors
`<T : NavKey> NavBackStack()`	Cmn
`<T : NavKey> NavBackStack(base: SnapshotStateList<T>)` Creates a new back stack backed by the provided `SnapshotStateList`.	Cmn
`<T : NavKey> NavBackStack(vararg elements: T)`	Cmn

Inherited functions

From kotlin.collections.List

`open operator Boolean`	`contains(element: T)`	Cmn
`open Boolean`	`containsAll(elements: Collection<T>)`	Cmn
`open operator T`	`get(index: Int)`	Cmn
`open Int`	`indexOf(element: T)`	Cmn
`open Boolean`	`isEmpty()`	Cmn
`open operator MutableIterator<T>`	`iterator()`	Cmn
`open Int`	`lastIndexOf(element: T)`	Cmn

From kotlin.collections.MutableList

`open Boolean`	`add(element: T)`	Cmn
`open Unit`	`add(index: Int, element: T)`	Cmn
`open Boolean`	`addAll(elements: Collection<T>)`	Cmn
`open Boolean`	`addAll(index: Int, elements: Collection<T>)`	Cmn
`open Unit`	`clear()`	Cmn
`open MutableListIterator<T>`	`listIterator()`	Cmn
`open MutableListIterator<T>`	`listIterator(index: Int)`	Cmn
`open Boolean`	`remove(element: T)`	Cmn
`open Boolean`	`removeAll(elements: Collection<T>)`	Cmn
`open T`	`removeAt(index: Int)`	Cmn
`open Boolean`	`retainAll(elements: Collection<T>)`	Cmn
`open operator T`	`set(index: Int, element: T)`	Cmn
`open MutableList<T>`	`subList(fromIndex: Int, toIndex: Int)`	Cmn

From androidx.compose.runtime.snapshots.StateObject

`open StateRecord?`	`mergeRecords( previous: StateRecord, current: StateRecord, applied: StateRecord )` Produce a merged state based on the conflicting state changes.	Cmn
`open Unit`	`prependStateRecord(value: StateRecord)` Add a new state record to the beginning of a list.	Cmn

Inherited properties

From kotlin.collections.List

open Int

size

Cmn

From androidx.compose.runtime.snapshots.StateObject

open StateRecord

firstStateRecord

The first state record in a linked list of state records.

Cmn

Public constructors

NavBackStack

Cmn

<T : NavKey> NavBackStack()

NavBackStack

Cmn

<T : NavKey> NavBackStack(base: SnapshotStateList<T>)

Creates a new back stack backed by the provided SnapshotStateList.

NavBackStack

Cmn

<T : NavKey> NavBackStack(vararg elements: T)