LoaderManager

Artifact: androidx.loader:loader

View Source

Added in 1.0.0

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Kotlin |Java

public abstract class LoaderManager

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Static library support version of the framework's android.app.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 androidx.fragment.app.FragmentActivity to use this.

Summary

Nested types
public interface LoaderManager.LoaderCallbacks<D> Callback interface for a client to interact with the manager.

Public constructors
LoaderManager()

Public methods
abstract void	@MainThread 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 is deprecated. Use enableDebugLogging 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 @NonNull LoaderManager	<T extends LifecycleOwner & ViewModelStoreOwner> getInstance(@NonNull T owner) Gets a LoaderManager associated with the given owner, such as a androidx.fragment.app.FragmentActivity or androidx.fragment.app.Fragment.
abstract @Nullable Loader<D>	<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 @NonNull Loader<D>	@MainThread <D> initLoader(     int id,     @Nullable Bundle args,     @NonNull LoaderManager.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 @NonNull Loader<D>	@MainThread <D> restartLoader(     int id,     @Nullable Bundle args,     @NonNull LoaderManager.LoaderCallbacks<D> callback ) Starts a new or restarts an existing android.content.Loader in this manager, registers the callbacks to it, and (if the activity/fragment is currently started) starts loading it.

Public constructors

LoaderManager

Added in 1.0.0

public LoaderManager()

Public methods

destroyLoader

Added in 1.0.0

@MainThread
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 onLoadFinished, a call will be made to onLoaderReset.

Must be called from the process's main thread.

dump

Added in 1.0.0

Deprecated in 1.0.0

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

This method is deprecated.

Use enableDebugLogging to understand the series of operations performed by LoaderManager.

Print the LoaderManager's state into the given stream.

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

enableDebugLogging

Added in 1.0.0

Deprecated in 1.2.0-alpha01

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.

getInstance

Added in 1.0.0

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

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

Parameters
<T extends LifecycleOwner & ViewModelStoreOwner>	A class that maintains its own android.arch.lifecycle.Lifecycle and android.arch.lifecycle.ViewModelStore. For instance, androidx.fragment.app.FragmentActivity or androidx.fragment.app.Fragment.
@NonNull T owner	The owner that should be used to create the returned LoaderManager

Returns
@NonNull LoaderManager	A valid LoaderManager

getLoader

Added in 1.0.0

public abstract @Nullable Loader<D> <D> getLoader(int id)

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

hasRunningLoaders

Added in 1.0.0

public boolean hasRunningLoaders()

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

initLoader

Added in 1.0.0

@MainThread
public abstract @NonNull Loader<D> <D> initLoader(
    int id,
    @Nullable Bundle args,
    @NonNull LoaderManager.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 onLoadFinished 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
int id	A unique identifier for this loader. Can be whatever you want. Identifiers are scoped to a particular LoaderManager instance.
@Nullable Bundle args	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.
@NonNull LoaderManager.LoaderCallbacks<D> callback	Interface the LoaderManager will call to report about changes in the state of the loader. Required.

markForRedelivery

Added in 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 onLoadFinished, this will ensure that onLoadFinished 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 onLoadFinished 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 1.0.0

@MainThread
public abstract @NonNull Loader<D> <D> restartLoader(
    int id,
    @Nullable Bundle args,
    @NonNull LoaderManager.LoaderCallbacks<D> callback
)

Starts a new or restarts an existing android.content.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
int id	A unique identifier for this loader. Can be whatever you want. Identifiers are scoped to a particular LoaderManager instance.
@Nullable Bundle args	Optional arguments to supply to the loader at construction.
@NonNull LoaderManager.LoaderCallbacks<D> callback	Interface the LoaderManager will call to report about changes in the state of the loader. Required.