FragmentManager

Kotlin |Java

abstract class FragmentManager

kotlin.Any
↳	androidx.fragment.app.FragmentManager

Static library support version of the framework's android.app.FragmentManager. Used to write apps that run on platforms prior to Android 3.0. When running on Android 3.0 or above, this implementation is still used; it does not try to switch to the framework's implementation. See the framework FragmentManager documentation for a class overview.

Your activity must derive from FragmentActivity to use this. From such an activity, you can acquire the FragmentManager by calling FragmentActivity#getSupportFragmentManager.

Summary

Nested classes
abstract	BackStackEntry Representation of an entry on the fragment back stack, as created with FragmentTransaction.addToBackStack().
abstract	FragmentLifecycleCallbacks Callback interface for listening to fragment state changes that happen within a given FragmentManager.
abstract	OnBackStackChangedListener Interface to watch for changes to the back stack.

Constants
static Int	POP_BACK_STACK_INCLUSIVE Flag for popBackStack(String, int) and popBackStack(int, int): If set, and the name or ID of a back stack entry has been supplied, then all matching entries will be consumed until one that doesn't match is found or the bottom of the stack is reached.

Public constructors
<init>() Static library support version of the framework's android.app.FragmentManager.

Public methods
open Unit	addOnBackStackChangedListener(@NonNull listener: FragmentManager.OnBackStackChangedListener) Add a new listener for changes to the fragment back stack.
open FragmentTransaction	beginTransaction() Start a series of edit operations on the Fragments associated with this FragmentManager.
open Unit	dump(@NonNull prefix: String, @Nullable fd: FileDescriptor?, @NonNull writer: PrintWriter, @Nullable args: Array<String!>?) Print the FragmentManager's state into the given stream.
open static Unit	enableDebugLogging(enabled: Boolean) Control whether the framework's internal fragment manager debugging logs are turned on.
open Boolean	executePendingTransactions() After a FragmentTransaction is committed with FragmentTransaction.commit(), it is scheduled to be executed asynchronously on the process's main thread.
open static F	findFragment(@NonNull view: View) Find a Fragment associated with the given View.
open Fragment?	findFragmentById(@IdRes id: Int) Finds a fragment that was identified by the given id either when inflated from XML or as the container ID when added in a transaction.
open Fragment?	findFragmentByTag(@Nullable tag: String?) Finds a fragment that was identified by the given tag either when inflated from XML or as supplied when added in a transaction.
open FragmentManager.BackStackEntry	getBackStackEntryAt(index: Int) Return the BackStackEntry at index index in the back stack; entries start index 0 being the bottom of the stack.
open Int	getBackStackEntryCount() Return the number of entries currently in the back stack.
open Fragment?	getFragment(@NonNull bundle: Bundle, @NonNull key: String) Retrieve the current Fragment instance for a reference previously placed with putFragment(Bundle, String, Fragment).
open FragmentFactory	getFragmentFactory() Gets the current FragmentFactory used to instantiate new Fragment instances.
open MutableList<Fragment!>	getFragments() Get a list of all fragments that are currently added to the FragmentManager.
open Fragment?	getPrimaryNavigationFragment() Return the currently active primary navigation fragment for this FragmentManager.
open Boolean	isDestroyed() Returns true if the final Activity.onDestroy() call has been made on the FragmentManager's Activity, so this instance is now dead.
open Boolean	isStateSaved() Returns true if the FragmentManager's state has already been saved by its host.
open Unit	popBackStack() Pop the top state off the back stack.
open Unit	popBackStack(@Nullable name: String?, flags: Int) Pop the last fragment transition from the manager's fragment back stack.
open Unit	popBackStack(id: Int, flags: Int) Pop all back stack states up to the one with the given identifier.
open Boolean	popBackStackImmediate() Like popBackStack(), but performs the operation immediately inside of the call.
open Boolean	popBackStackImmediate(@Nullable name: String?, flags: Int) Like popBackStack(String, int), but performs the operation immediately inside of the call.
open Boolean	popBackStackImmediate(id: Int, flags: Int) Like popBackStack(int, int), but performs the operation immediately inside of the call.
open Unit	putFragment(@NonNull bundle: Bundle, @NonNull key: String, @NonNull fragment: Fragment) Put a reference to a fragment in a Bundle.
open Unit	registerFragmentLifecycleCallbacks(@NonNull cb: FragmentManager.FragmentLifecycleCallbacks, recursive: Boolean) Registers a FragmentLifecycleCallbacks to listen to fragment lifecycle events happening in this FragmentManager.
open Unit	removeOnBackStackChangedListener(@NonNull listener: FragmentManager.OnBackStackChangedListener) Remove a listener that was previously added with addOnBackStackChangedListener(OnBackStackChangedListener).
open Fragment.SavedState?	saveFragmentInstanceState(@NonNull fragment: Fragment) Save the current instance state of the given Fragment.
open Unit	setFragmentFactory(@NonNull fragmentFactory: FragmentFactory) Set a FragmentFactory for this FragmentManager that will be used to create new Fragment instances from this point onward.
open String	toString()
open Unit	unregisterFragmentLifecycleCallbacks(@NonNull cb: FragmentManager.FragmentLifecycleCallbacks) Unregisters a previously registered FragmentLifecycleCallbacks.

Extension functions

From androidx.fragment.app Unit FragmentManager.commit(allowStateLoss: Boolean = false, body: FragmentTransaction.() -> Unit) Run body in a FragmentTransaction which is automatically committed if it completes without exception. Unit FragmentManager.commitNow(allowStateLoss: Boolean = false, body: FragmentTransaction.() -> Unit) Run body in a FragmentTransaction which is automatically committed if it completes without exception. Unit FragmentManager.transaction(now: Boolean = false, allowStateLoss: Boolean = false, body: FragmentTransaction.() -> Unit) Run body in a FragmentTransaction which is automatically committed if it completes without exception.

Constants

POP_BACK_STACK_INCLUSIVE

static val POP_BACK_STACK_INCLUSIVE: Int

Flag for popBackStack(String, int) and popBackStack(int, int): If set, and the name or ID of a back stack entry has been supplied, then all matching entries will be consumed until one that doesn't match is found or the bottom of the stack is reached. Otherwise, all entries up to but not including that entry will be removed.

Value: 1

Public constructors

<init>

FragmentManager()

Static library support version of the framework's android.app.FragmentManager. Used to write apps that run on platforms prior to Android 3.0. When running on Android 3.0 or above, this implementation is still used; it does not try to switch to the framework's implementation. See the framework FragmentManager documentation for a class overview.

Your activity must derive from FragmentActivity to use this. From such an activity, you can acquire the FragmentManager by calling FragmentActivity#getSupportFragmentManager.

Public methods

addOnBackStackChangedListener

open fun addOnBackStackChangedListener(@NonNull listener: FragmentManager.OnBackStackChangedListener): Unit

Add a new listener for changes to the fragment back stack.

beginTransaction

@NonNull open fun beginTransaction(): FragmentTransaction

Start a series of edit operations on the Fragments associated with this FragmentManager.

Note: A fragment transaction can only be created/committed prior to an activity saving its state. If you try to commit a transaction after FragmentActivity.onSaveInstanceState() (and prior to a following FragmentActivity.onStart or FragmentActivity.onResume(), you will get an error. This is because the framework takes care of saving your current fragments in the state, and if changes are made after the state is saved then they will be lost.

dump

open fun dump(@NonNull prefix: String, @Nullable fd: FileDescriptor?, @NonNull writer: PrintWriter, @Nullable args: Array<String!>?): Unit

Print the FragmentManager's state into the given stream.

Parameters
prefix	String: Text to print at the front of each line.
fd	String: The raw file descriptor that the dump is being sent to.
writer	String: A PrintWriter to which the dump is to be set.
args	String: Additional arguments to the dump request.

enableDebugLogging

open static fun enableDebugLogging(enabled: Boolean): Unit

Control whether the framework's internal fragment manager debugging logs are turned on. If enabled, you will see output in logcat as the framework performs fragment operations.

executePendingTransactions

open fun executePendingTransactions(): Boolean

After a FragmentTransaction is committed with FragmentTransaction.commit(), it is scheduled to be executed asynchronously on the process's main thread. If you want to immediately executing any such pending operations, you can call this function (only from the main thread) to do so. Note that all callbacks and other related behavior will be done from within this call, so be careful about where this is called from.

If you are committing a single transaction that does not modify the fragment back stack, strongly consider using FragmentTransaction#commitNow() instead. This can help avoid unwanted side effects when other code in your app has pending committed transactions that expect different timing.

This also forces the start of any postponed Transactions where Fragment#postponeEnterTransition() has been called.

Return
Boolean: Returns true if there were any pending transactions to be executed.

findFragment

@NonNull open static fun <F : Fragment!> findFragment(@NonNull view: View): F

Find a Fragment associated with the given View. This method will locate the Fragment associated with this view. This is automatically populated for the View returned by Fragment#onCreateView and its children.

Parameters
view	View: the view to search from

Return
F: the locally scoped Fragment to the given view

Exceptions
IllegalStateException	if the given view does not correspond with a Fragment.

findFragmentById

@Nullable open fun findFragmentById(@IdRes id: Int): Fragment?

Finds a fragment that was identified by the given id either when inflated from XML or as the container ID when added in a transaction. This first searches through fragments that are currently added to the manager's activity; if no such fragment is found, then all fragments currently on the back stack associated with this ID are searched.

Return
Fragment?: The fragment if found or null otherwise.

findFragmentByTag

@Nullable open fun findFragmentByTag(@Nullable tag: String?): Fragment?

Finds a fragment that was identified by the given tag either when inflated from XML or as supplied when added in a transaction. This first searches through fragments that are currently added to the manager's activity; if no such fragment is found, then all fragments currently on the back stack are searched.

Return
Fragment?: The fragment if found or null otherwise.

getBackStackEntryAt

@NonNull open fun getBackStackEntryAt(index: Int): FragmentManager.BackStackEntry

Return the BackStackEntry at index index in the back stack; entries start index 0 being the bottom of the stack.

getBackStackEntryCount

open fun getBackStackEntryCount(): Int

Return the number of entries currently in the back stack.

getFragment

@Nullable open fun getFragment(@NonNull bundle: Bundle, @NonNull key: String): Fragment?

Retrieve the current Fragment instance for a reference previously placed with putFragment(Bundle, String, Fragment).

Parameters
bundle	Bundle: The bundle from which to retrieve the fragment reference.
key	Bundle: The name of the entry in the bundle.

Return
Fragment?: Returns the current Fragment instance that is associated with the given reference.

getFragmentFactory

@NonNull open fun getFragmentFactory(): FragmentFactory

Gets the current FragmentFactory used to instantiate new Fragment instances.

Return
FragmentFactory: the current FragmentFactory

getFragments

@NonNull open fun getFragments(): MutableList<Fragment!>

Get a list of all fragments that are currently added to the FragmentManager. This may include those that are hidden as well as those that are shown. This will not include any fragments only in the back stack, or fragments that are detached or removed.

The order of the fragments in the list is the order in which they were added or attached.

Return
MutableList<Fragment!>: A list of all fragments that are added to the FragmentManager.

getPrimaryNavigationFragment

@Nullable open fun getPrimaryNavigationFragment(): Fragment?

Return the currently active primary navigation fragment for this FragmentManager. The primary navigation fragment is set by fragment transactions using FragmentTransaction#setPrimaryNavigationFragment(Fragment).

The primary navigation fragment's child FragmentManager will be called first to process delegated navigation actions such as popBackStack() if no ID or transaction name is provided to pop to.

Return
Fragment?: the fragment designated as the primary navigation fragment

isDestroyed

open fun isDestroyed(): Boolean

Returns true if the final Activity.onDestroy() call has been made on the FragmentManager's Activity, so this instance is now dead.

isStateSaved

open fun isStateSaved(): Boolean

Returns true if the FragmentManager's state has already been saved by its host. Any operations that would change saved state should not be performed if this method returns true. For example, any popBackStack() method, such as popBackStackImmediate() or any FragmentTransaction using FragmentTransaction#commit() instead of FragmentTransaction#commitAllowingStateLoss() will change the state and will result in an error.

Return
Boolean: true if this FragmentManager's state has already been saved by its host

popBackStack

open fun popBackStack(): Unit

Pop the top state off the back stack. This function is asynchronous -- it enqueues the request to pop, but the action will not be performed until the application returns to its event loop.

popBackStack

open fun popBackStack(@Nullable name: String?, flags: Int): Unit

Pop the last fragment transition from the manager's fragment back stack. This function is asynchronous -- it enqueues the request to pop, but the action will not be performed until the application returns to its event loop.

Parameters
name	String?: If non-null, this is the name of a previous back state to look for; if found, all states up to that state will be popped. The POP_BACK_STACK_INCLUSIVE flag can be used to control whether the named state itself is popped. If null, only the top state is popped.
flags	String?: Either 0 or POP_BACK_STACK_INCLUSIVE.

popBackStack

open fun popBackStack(id: Int, flags: Int): Unit

Pop all back stack states up to the one with the given identifier. This function is asynchronous -- it enqueues the request to pop, but the action will not be performed until the application returns to its event loop.

Parameters
id	Int: Identifier of the stated to be popped. If no identifier exists, false is returned. The identifier is the number returned by FragmentTransaction.commit(). The POP_BACK_STACK_INCLUSIVE flag can be used to control whether the named state itself is popped.
flags	Int: Either 0 or POP_BACK_STACK_INCLUSIVE.

popBackStackImmediate

open fun popBackStackImmediate(): Boolean

Like popBackStack(), but performs the operation immediately inside of the call. This is like calling executePendingTransactions() afterwards without forcing the start of postponed Transactions.

Return
Boolean: Returns true if there was something popped, else false.

popBackStackImmediate

open fun popBackStackImmediate(@Nullable name: String?, flags: Int): Boolean

Like popBackStack(String, int), but performs the operation immediately inside of the call. This is like calling executePendingTransactions() afterwards without forcing the start of postponed Transactions.

Return
Boolean: Returns true if there was something popped, else false.

popBackStackImmediate

open fun popBackStackImmediate(id: Int, flags: Int): Boolean

Like popBackStack(int, int), but performs the operation immediately inside of the call. This is like calling executePendingTransactions() afterwards without forcing the start of postponed Transactions.

Return
Boolean: Returns true if there was something popped, else false.

putFragment

open fun putFragment(@NonNull bundle: Bundle, @NonNull key: String, @NonNull fragment: Fragment): Unit

Put a reference to a fragment in a Bundle. This Bundle can be persisted as saved state, and when later restoring getFragment(Bundle, String) will return the current instance of the same fragment.

Parameters
bundle	Bundle: The bundle in which to put the fragment reference.
key	Bundle: The name of the entry in the bundle.
fragment	Bundle: The Fragment whose reference is to be stored.

registerFragmentLifecycleCallbacks

open fun registerFragmentLifecycleCallbacks(@NonNull cb: FragmentManager.FragmentLifecycleCallbacks, recursive: Boolean): Unit

Registers a FragmentLifecycleCallbacks to listen to fragment lifecycle events happening in this FragmentManager. All registered callbacks will be automatically unregistered when this FragmentManager is destroyed.

Parameters
cb	FragmentManager.FragmentLifecycleCallbacks: Callbacks to register
recursive	FragmentManager.FragmentLifecycleCallbacks: true to automatically register this callback for all child FragmentManagers

removeOnBackStackChangedListener

open fun removeOnBackStackChangedListener(@NonNull listener: FragmentManager.OnBackStackChangedListener): Unit

Remove a listener that was previously added with addOnBackStackChangedListener(OnBackStackChangedListener).

saveFragmentInstanceState

@Nullable open fun saveFragmentInstanceState(@NonNull fragment: Fragment): Fragment.SavedState?

Save the current instance state of the given Fragment. This can be used later when creating a new instance of the Fragment and adding it to the fragment manager, to have it create itself to match the current state returned here. Note that there are limits on how this can be used:

• The Fragment must currently be attached to the FragmentManager.
• A new Fragment created using this saved state must be the same class type as the Fragment it was created from.
• The saved state can not contain dependencies on other fragments -- that is it can't use putFragment(Bundle, String, Fragment) to store a fragment reference because that reference may not be valid when this saved state is later used. Likewise the Fragment's target and result code are not included in this state.

Parameters
fragment	Fragment: The Fragment whose state is to be saved.

Return
Fragment.SavedState?: The generated state. This will be null if there was no interesting state created by the fragment.

setFragmentFactory

open fun setFragmentFactory(@NonNull fragmentFactory: FragmentFactory): Unit

Set a FragmentFactory for this FragmentManager that will be used to create new Fragment instances from this point onward.

Parameters
fragmentFactory	FragmentFactory: the factory to use to create new Fragment instances

toString

@NonNull open fun toString(): String

unregisterFragmentLifecycleCallbacks

open fun unregisterFragmentLifecycleCallbacks(@NonNull cb: FragmentManager.FragmentLifecycleCallbacks): Unit

Unregisters a previously registered FragmentLifecycleCallbacks. If the callback was not previously registered this call has no effect. All registered callbacks will be automatically unregistered when this FragmentManager is destroyed.

Parameters
cb	FragmentManager.FragmentLifecycleCallbacks: Callbacks to unregister