CursorLoader

Added in 1.0.0

Kotlin |Java

public class CursorLoader extends AsyncTaskLoader

java.lang.Object
↳	androidx.loader.content.Loader
	↳	androidx.loader.content.AsyncTaskLoader
		↳	androidx.loader.content.CursorLoader

Static library support version of the framework's android.content.CursorLoader. 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.

Summary

Public constructors
`CursorLoader(@NonNull Context context)` Creates an empty unspecified CursorLoader.
`CursorLoader( @NonNull Context context, @NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder )` Creates a fully-specified CursorLoader.

Public methods
`void`	`cancelLoadInBackground()` Called on the main thread to abort a load in progress.
`void`	`deliverResult(Cursor data)` Sends the result of the load to the registered listener.
`void`	`dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args)` This method is deprecated. Consider using `enableDebugLogging` to understand the series of operations performed by LoaderManager.
`@Nullable String[]`	`getProjection()`
`@Nullable String`	`getSelection()`
`@Nullable String[]`	`getSelectionArgs()`
`@Nullable String`	`getSortOrder()`
`@NonNull Uri`	`getUri()`
`Cursor`	`loadInBackground()` Called on a worker thread to perform the actual load and to return the result of the load operation.
`void`	`onCanceled(Cursor data)` Called if the task was canceled before it was completed.
`void`	`setProjection(@Nullable String[] projection)`
`void`	`setSelection(@Nullable String selection)`
`void`	`setSelectionArgs(@Nullable String[] selectionArgs)`
`void`	`setSortOrder(@Nullable String sortOrder)`
`void`	`setUri(@NonNull Uri uri)`

Protected methods
`void`	`onReset()` Subclasses must implement this to take care of resetting their loader, as per `reset`.
`void`	`onStartLoading()` Starts an asynchronous load of the contacts list data.
`void`	`onStopLoading()` Must be called from the UI thread

Inherited methods

From androidx.loader.content.AsyncTaskLoader

`@NonNull Executor`	`getExecutor()` Returns the `Executor` to use for this `Loader`'s `AsyncTask`s.
`boolean`	`isLoadInBackgroundCanceled()` Returns true if the current invocation of `loadInBackground` is being canceled.
`boolean`	`onCancelLoad()` Subclasses must implement this to take care of requests to `cancelLoad`.
`void`	`onForceLoad()` Subclasses must implement this to take care of requests to `forceLoad`.
`@Nullable D`	`onLoadInBackground()` Calls `loadInBackground`.
`void`	`setUpdateThrottle(long delayMS)` Set amount to throttle updates by.

From androidx.loader.content.Loader

`void`	`@MainThread abandon()` This function will normally be called for you automatically by `LoaderManager` when restarting a Loader.
`boolean`	`@MainThread cancelLoad()` Attempt to cancel the current load task.
`void`	`commitContentChanged()` Commit that you have actually fully processed a content change that was returned by `takeContentChanged`.
`@NonNull String`	`dataToString(@Nullable D data)` For debugging, converts an instance of the Loader's data class to a string that can be printed.
`void`	`@MainThread deliverCancellation()` Informs the registered `OnLoadCanceledListener` that the load has been canceled.
`void`	`@MainThread forceLoad()` Force an asynchronous load.
`@NonNull Context`	`getContext()`
`int`	`getId()`
`boolean`	`isAbandoned()` Return whether this loader has been abandoned.
`boolean`	`isReset()` Return whether this load has been reset.
`boolean`	`isStarted()` Return whether this load has been started.
`void`	`@MainThread onAbandon()` Subclasses implement this to take care of being abandoned.
`void`	`@MainThread onContentChanged()` Called when `ForceLoadContentObserver` detects a change.
`void`	`@MainThread registerListener( int id, @NonNull Loader.OnLoadCompleteListener<D> listener )` Registers a class that will receive callbacks when a load is complete.
`void`	`@MainThread registerOnLoadCanceledListener( @NonNull Loader.OnLoadCanceledListener<D> listener )` Registers a listener that will receive callbacks when a load is canceled.
`void`	`@MainThread reset()` This function will normally be called for you automatically by `LoaderManager` when destroying a Loader.
`void`	`rollbackContentChanged()` Report that you have abandoned the processing of a content change that was returned by `takeContentChanged` and would like to rollback to the state where there is again a pending content change.
`final void`	`@MainThread startLoading()` This function will normally be called for you automatically by `LoaderManager` when the associated fragment/activity is being started.
`void`	`@MainThread stopLoading()` This function will normally be called for you automatically by `LoaderManager` when the associated fragment/activity is being stopped.
`boolean`	`takeContentChanged()` Take the current flag indicating whether the loader's content had changed while it was stopped.
`@NonNull String`	`toString()`
`void`	`@MainThread unregisterListener(@NonNull Loader.OnLoadCompleteListener<D> listener)` Remove a listener that was previously added with `registerListener`.
`void`	`@MainThread unregisterOnLoadCanceledListener( @NonNull Loader.OnLoadCanceledListener<D> listener )` Unregisters a listener that was previously added with `registerOnLoadCanceledListener`.

Public constructors

CursorLoader

Added in 1.0.0

public CursorLoader(@NonNull Context context)

Creates an empty unspecified CursorLoader. You must follow this with calls to setUri, setSelection, etc to specify the query to perform.

CursorLoader

Added in 1.0.0

public CursorLoader(
    @NonNull Context context,
    @NonNull Uri uri,
    @Nullable String[] projection,
    @Nullable String selection,
    @Nullable String[] selectionArgs,
    @Nullable String sortOrder
)

Creates a fully-specified CursorLoader. See ContentResolver.query() for documentation on the meaning of the parameters. These will be passed as-is to that call.

Public methods

cancelLoadInBackground

public void cancelLoadInBackground()

Called on the main thread to abort a load in progress. Override this method to abort the current invocation of loadInBackground that is running in the background on a worker thread. This method should do nothing if loadInBackground has not started running or if it has already finished.

See also
`loadInBackground`

deliverResult

Added in 1.0.0

public void deliverResult(Cursor data)

Sends the result of the load to the registered listener. Should only be called by subclasses. Must be called from the process's main thread.

Parameters
`Cursor data`	the result of the load

dump

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

getProjection

Added in 1.0.0

public @Nullable String[] getProjection()

getSelection

Added in 1.0.0

public @Nullable String getSelection()

getSelectionArgs

Added in 1.0.0

public @Nullable String[] getSelectionArgs()

getSortOrder

Added in 1.0.0

public @Nullable String getSortOrder()

getUri

Added in 1.0.0

public @NonNull Uri getUri()

loadInBackground

Added in 1.2.0-alpha01

public Cursor loadInBackground()

Called on a worker thread to perform the actual load and to return the result of the load operation. Implementations should not deliver the result directly, but should return them from this method, which will eventually end up calling deliverResult on the UI thread. If implementations need to process the results on the UI thread they may override deliverResult and do so there. To support cancellation, this method should periodically check the value of isLoadInBackgroundCanceled and terminate when it returns true. Subclasses may also override cancelLoadInBackground to interrupt the load directly instead of polling isLoadInBackgroundCanceled. When the load is canceled, this method may either return normally or throw OperationCanceledException. In either case, the Loader will call onCanceled to perform post-cancellation cleanup and to dispose of the result object, if any.

Returns
`Cursor`	The result of the load operation.

Throws
`androidx.core.os.OperationCanceledException`	if the load is canceled during execution.

See also
`isLoadInBackgroundCanceled`
`cancelLoadInBackground`
`onCanceled`

onCanceled

Added in 1.0.0

public void onCanceled(Cursor data)

Called if the task was canceled before it was completed. Gives the class a chance to clean up post-cancellation and to properly dispose of the result.

Parameters
`Cursor data`	The value that was returned by `loadInBackground`, or null if the task threw `OperationCanceledException`.

setProjection

Added in 1.0.0

public void setProjection(@Nullable String[] projection)

setSelection

Added in 1.0.0

public void setSelection(@Nullable String selection)

setSelectionArgs

Added in 1.0.0

public void setSelectionArgs(@Nullable String[] selectionArgs)

setSortOrder

Added in 1.0.0

public void setSortOrder(@Nullable String sortOrder)

setUri

Added in 1.0.0

public void setUri(@NonNull Uri uri)

Protected methods

onReset

protected void onReset()

Subclasses must implement this to take care of resetting their loader, as per reset. This is not called by clients directly, but as a result of a call to reset. This will always be called from the process's main thread.

onStartLoading

protected void onStartLoading()

Starts an asynchronous load of the contacts list data. When the result is ready the callbacks will be called on the UI thread. If a previous load has been completed and is still valid the result may be passed to the callbacks immediately. Must be called from the UI thread

onStopLoading

protected void onStopLoading()

Must be called from the UI thread