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added in version 1.0.0
belongs to Maven artifact androidx.loader:loader:1.0.0-rc01

LoaderManager

public abstract class LoaderManager
extends Object

java.lang.Object
   ↳ androidx.loader.app.LoaderManager


Static library support version of the framework's LoaderManager. 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 SDK documentation for a class overview.

Your activity must derive from FragmentActivity to use this.

Summary

Nested classes

interface LoaderManager.LoaderCallbacks<D>

Callback interface for a client to interact with the manager. 

Public constructors

LoaderManager()

Public methods

abstract void destroyLoader(int id)

Stops and removes the loader with the given ID.

abstract void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args)

This method was deprecated in API level 1.0.0. Use enableDebugLogging(boolean) to understand the series of operations performed by LoaderManager.

static void enableDebugLogging(boolean enabled)

Control whether the framework's internal loader manager debugging logs are turned on.

static <T extends LifecycleOwner & ViewModelStoreOwner> LoaderManager getInstance(T owner)

Gets a LoaderManager associated with the given owner, such as a FragmentActivity or Fragment.

abstract <D> Loader<D> getLoader(int id)

Return the Loader with the given id or null if no matching Loader is found.

boolean hasRunningLoaders()

Returns true if any loaders managed are currently running and have not returned data to the application yet.

abstract <D> Loader<D> initLoader(int id, Bundle args, LoaderCallbacks<D> callback)

Ensures a loader is initialized and active.

abstract void markForRedelivery()

Mark all Loaders associated with this LoaderManager for redelivery of their current data (if any), waiting for the next time the Loader is started if it is currently stopped.

abstract <D> Loader<D> restartLoader(int id, Bundle args, LoaderCallbacks<D> callback)

Starts a new or restarts an existing Loader in this manager, registers the callbacks to it, and (if the activity/fragment is currently started) starts loading it.

Inherited methods

Public constructors

LoaderManager

added in version 1.0.0
public LoaderManager ()

Public methods

destroyLoader

added in version 1.0.0
public abstract void destroyLoader (int id)

Stops and removes the loader with the given ID. If this loader had previously reported data to the client through LoaderManager.LoaderCallbacks.onLoadFinished(Loader, Object), a call will be made to LoaderManager.LoaderCallbacks.onLoaderReset(Loader).

Must be called from the process's main thread.

Parameters
id int

dump

added in version 1.0.0
public abstract void dump (String prefix, 
                FileDescriptor fd, 
                PrintWriter writer, 
                String[] args)

This method was deprecated in API level 1.0.0.
Use enableDebugLogging(boolean) to understand the series of operations performed by LoaderManager.

Print the LoaderManager's state into the given stream.

Parameters
prefix String: Text to print at the front of each line.

fd FileDescriptor: The raw file descriptor that the dump is being sent to.

writer PrintWriter: A PrintWriter to which the dump is to be set.

args String: Additional arguments to the dump request.

enableDebugLogging

added in version 1.0.0
public static void enableDebugLogging (boolean enabled)

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

Parameters
enabled boolean

getInstance

added in version 1.0.0
public static LoaderManager getInstance (T owner)

Gets a LoaderManager associated with the given owner, such as a FragmentActivity or Fragment.

Parameters
owner T: The owner that should be used to create the returned LoaderManager

Returns
LoaderManager A valid LoaderManager

getLoader

added in version 1.0.0
public abstract Loader<D> getLoader (int id)

Return the Loader with the given id or null if no matching Loader is found.

Parameters
id int

Returns
Loader<D>

hasRunningLoaders

added in version 1.0.0
public boolean hasRunningLoaders ()

Returns true if any loaders managed are currently running and have not returned data to the application yet.

Returns
boolean

initLoader

added in version 1.0.0
public abstract Loader<D> initLoader (int id, 
                Bundle args, 
                LoaderCallbacks<D> callback)

Ensures a loader is initialized and active. If the loader doesn't already exist, one is created and (if the activity/fragment is currently started) starts the loader. Otherwise the last created loader is re-used.

In either case, the given callback is associated with the loader, and will be called as the loader state changes. If at the point of call the caller is in its started state, and the requested loader already exists and has generated its data, then callback LoaderManager.LoaderCallbacks.onLoadFinished(Loader, D) will be called immediately (inside of this function), so you must be prepared for this to happen.

Must be called from the process's main thread.

Parameters
id int: A unique identifier for this loader. Can be whatever you want. Identifiers are scoped to a particular LoaderManager instance.

args Bundle: Optional arguments to supply to the loader at construction. If a loader already exists (a new one does not need to be created), this parameter will be ignored and the last arguments continue to be used.

callback LoaderCallbacks: Interface the LoaderManager will call to report about changes in the state of the loader. Required.

Returns
Loader<D>

markForRedelivery

added in version 1.0.0
public abstract void markForRedelivery ()

Mark all Loaders associated with this LoaderManager for redelivery of their current data (if any), waiting for the next time the Loader is started if it is currently stopped. In cases where no data has yet been delivered, this is effectively a no-op. In cases where data has already been delivered via LoaderManager.LoaderCallbacks.onLoadFinished(Loader, Object), this will ensure that LoaderManager.LoaderCallbacks.onLoadFinished(Loader, Object) is called again with the same data.

Call this only if you are implementing a LifecycleOwner where the views/elements that developers are likely to use in LoaderManager.LoaderCallbacks.onLoadFinished(Loader, Object) can be created and destroyed multiple times without the LifecycleOwner itself being destroyed. Call this when the views/elements are being destroyed to ensure that the data is redelivered upon recreation.

restartLoader

added in version 1.0.0
public abstract Loader<D> restartLoader (int id, 
                Bundle args, 
                LoaderCallbacks<D> callback)

Starts a new or restarts an existing Loader in this manager, registers the callbacks to it, and (if the activity/fragment is currently started) starts loading it. If a loader with the same id has previously been started it will automatically be destroyed when the new loader completes its work. The callback will be delivered before the old loader is destroyed.

Must be called from the process's main thread.

Parameters
id int: A unique identifier for this loader. Can be whatever you want. Identifiers are scoped to a particular LoaderManager instance.

args Bundle: Optional arguments to supply to the loader at construction.

callback LoaderCallbacks: Interface the LoaderManager will call to report about changes in the state of the loader. Required.

Returns
Loader<D>