Loader
public class Loader<D>
AsyncTaskLoader |
Static library support version of the framework's |
CursorLoader |
Static library support version of the framework's |
Static library support version of the framework's android.content.Loader. 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
Nested types |
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public final inner class Loader.ForceLoadContentObserver extends ContentObserverAn implementation of a ContentObserver that takes care of connecting it to the Loader to have the loader re-load its data when the observer is told it has changed. |
public interface Loader.OnLoadCanceledListener<D>Interface that is implemented to discover when a Loader has been canceled before it finished loading its data. |
public interface Loader.OnLoadCompleteListener<D>Interface that is implemented to discover when a Loader has finished loading its data. |
Public constructors |
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Stores away the application context associated with context. |
Public methods |
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void |
This function will normally be called for you automatically by |
boolean |
Attempt to cancel the current load task. |
void |
Commit that you have actually fully processed a content change that was returned by |
@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 |
Informs the registered |
void |
@MainThreadSends the result of the load to the registered listener. |
void |
This method is deprecated. Consider using |
void |
Force an asynchronous load. |
@NonNull Context |
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int |
getId() |
boolean |
Return whether this loader has been abandoned. |
boolean |
isReset()Return whether this load has been reset. |
boolean |
Return whether this load has been started. |
void |
Called when |
void |
@MainThreadRegisters a class that will receive callbacks when a load is complete. |
void |
Registers a listener that will receive callbacks when a load is canceled. |
void |
This function will normally be called for you automatically by |
void |
Report that you have abandoned the processing of a content change that was returned by |
final void |
This function will normally be called for you automatically by |
void |
This function will normally be called for you automatically by |
boolean |
Take the current flag indicating whether the loader's content had changed while it was stopped. |
@NonNull String |
toString() |
void |
@MainThreadRemove a listener that was previously added with |
void |
Unregisters a listener that was previously added with |
Protected methods |
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void |
Subclasses implement this to take care of being abandoned. |
boolean |
Subclasses must implement this to take care of requests to |
void |
Subclasses must implement this to take care of requests to |
void |
Subclasses must implement this to take care of resetting their loader, as per |
void |
Subclasses must implement this to take care of loading their data, as per |
void |
Subclasses must implement this to take care of stopping their loader, as per |
Public constructors
Loader
public Loader(@NonNull Context context)
Stores away the application context associated with context. Since Loaders can be used across multiple activities it's dangerous to store the context directly; always use getContext to retrieve the Loader's Context, don't use the constructor argument directly. The Context returned by getContext is safe to use across Activity instances.
Public methods
abandon
@MainThread
public void abandon()
This function will normally be called for you automatically by LoaderManager when restarting a Loader. When using a Loader with LoaderManager, you must not call this method yourself, or you will conflict with its management of the Loader. Tell the Loader that it is being abandoned. This is called prior to reset to have it retain its current data but not report any new data.
Must be called from the process's main thread.
cancelLoad
@MainThread
public boolean cancelLoad()
Attempt to cancel the current load task. Must be called on the main thread of the process.
Cancellation is not an immediate operation, since the load is performed in a background thread. If there is currently a load in progress, this method requests that the load be canceled, and notes this is the case; once the background thread has completed its work its remaining state will be cleared. If another load request comes in during this time, it will be held until the canceled load is complete.
| Returns | |
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boolean |
Returns false if the task could not be canceled, typically because it has already completed normally, or because |
commitContentChanged
public void commitContentChanged()
Commit that you have actually fully processed a content change that was returned by takeContentChanged. This is for use with rollbackContentChanged to handle situations where a load is cancelled. Call this when you have completely processed a load without it being cancelled.
dataToString
public @NonNull String dataToString(@Nullable D data)
For debugging, converts an instance of the Loader's data class to a string that can be printed. Must handle a null data.
deliverCancellation
@MainThread
public void deliverCancellation()
Informs the registered OnLoadCanceledListener that the load has been canceled. Should only be called by subclasses. Must be called from the process's main thread.
deliverResult
@MainThread
public void deliverResult(@Nullable D 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 | |
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@Nullable D data |
the result of the load |
public voiddump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args)
Print the Loader's state into the given stream.
| Parameters | |
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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. |
forceLoad
@MainThread
public void forceLoad()
Force an asynchronous load. Unlike startLoading this will ignore a previously loaded data set and load a new one. This simply calls through to the implementation's onForceLoad. You generally should only call this when the loader is started -- that is, isStarted returns true.
Must be called from the process's main thread.
isAbandoned
public boolean isAbandoned()
Return whether this loader has been abandoned. In this state, the loader must not report any new data, and must keep its last reported data valid until it is finally reset.
isReset
public boolean isReset()
Return whether this load has been reset. That is, either the loader has not yet been started for the first time, or its reset has been called.
isStarted
public boolean isStarted()
Return whether this load has been started. That is, its startLoading has been called and no calls to stopLoading or reset have yet been made.
onContentChanged
@MainThread
public void onContentChanged()
Called when ForceLoadContentObserver detects a change. The default implementation checks to see if the loader is currently started; if so, it simply calls forceLoad; otherwise, it sets a flag so that takeContentChanged returns true.
Must be called from the process's main thread.
registerListener
@MainThread
public void registerListener(
int id,
@NonNull Loader.OnLoadCompleteListener<D> listener
)
Registers a class that will receive callbacks when a load is complete. The callback will be called on the process's main thread so it's safe to pass the results to widgets.
Must be called from the process's main thread.
registerOnLoadCanceledListener
@MainThread
public void registerOnLoadCanceledListener(
@NonNull Loader.OnLoadCanceledListener<D> listener
)
Registers a listener that will receive callbacks when a load is canceled. The callback will be called on the process's main thread so it's safe to pass the results to widgets. Must be called from the process's main thread.
| Parameters | |
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@NonNull Loader.OnLoadCanceledListener<D> listener |
The listener to register. |
reset
@MainThread
public void reset()
This function will normally be called for you automatically by LoaderManager when destroying a Loader. When using a Loader with LoaderManager, you must not call this method yourself, or you will conflict with its management of the Loader. Resets the state of the Loader. The Loader should at this point free all of its resources, since it may never be called again; however, its startLoading may later be called at which point it must be able to start running again.
This updates the Loader's internal state so that isStarted and isReset will return the correct values, and then calls the implementation's onReset.
Must be called from the process's main thread.
rollbackContentChanged
public 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. This is to handle the case where a data load due to a content change has been canceled before its data was delivered back to the loader.
startLoading
@MainThread
public final void startLoading()
This function will normally be called for you automatically by LoaderManager when the associated fragment/activity is being started. When using a Loader with LoaderManager, you must not call this method yourself, or you will conflict with its management of the Loader. Starts an asynchronous load of the Loader's data. When the result is ready the callbacks will be called on the process's main thread. If a previous load has been completed and is still valid the result may be passed to the callbacks immediately. The loader will monitor the source of the data set and may deliver future callbacks if the source changes. Calling stopLoading will stop the delivery of callbacks.
This updates the Loader's internal state so that isStarted and isReset will return the correct values, and then calls the implementation's onStartLoading.
Must be called from the process's main thread.
stopLoading
@MainThread
public void stopLoading()
This function will normally be called for you automatically by LoaderManager when the associated fragment/activity is being stopped. When using a Loader with LoaderManager, you must not call this method yourself, or you will conflict with its management of the Loader.
Stops delivery of updates until the next time startLoading is called. Implementations should not invalidate their data at this point -- clients are still free to use the last data the loader reported. They will, however, typically stop reporting new data if the data changes; they can still monitor for changes, but must not report them to the client until and if startLoading is later called.
This updates the Loader's internal state so that isStarted will return the correct value, and then calls the implementation's onStopLoading.
Must be called from the process's main thread.
takeContentChanged
public boolean takeContentChanged()
Take the current flag indicating whether the loader's content had changed while it was stopped. If it had, true is returned and the flag is cleared.
unregisterListener
@MainThread
public void unregisterListener(@NonNull Loader.OnLoadCompleteListener<D> listener)
Remove a listener that was previously added with registerListener. Must be called from the process's main thread.
unregisterOnLoadCanceledListener
@MainThread
public void unregisterOnLoadCanceledListener(
@NonNull Loader.OnLoadCanceledListener<D> listener
)
Unregisters a listener that was previously added with registerOnLoadCanceledListener. Must be called from the process's main thread.
| Parameters | |
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@NonNull Loader.OnLoadCanceledListener<D> listener |
The listener to unregister. |
Protected methods
onAbandon
@MainThread
protected void onAbandon()
Subclasses implement this to take care of being abandoned. This is an optional intermediate state prior to onReset -- it means that the client is no longer interested in any new data from the loader, so the loader must not report any further updates. However, the loader must keep its last reported data valid until the final onReset happens. You can retrieve the current abandoned state with isAbandoned. This will always be called from the process's main thread.
onCancelLoad
@MainThread
protected boolean onCancelLoad()
Subclasses must implement this to take care of requests to cancelLoad. This will always be called from the process's main thread.
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boolean |
Returns false if the task could not be canceled, typically because it has already completed normally, or because |
onForceLoad
@MainThread
protected void onForceLoad()
Subclasses must implement this to take care of requests to forceLoad. This will always be called from the process's main thread.
onReset
@MainThread
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
@MainThread
protected void onStartLoading()
Subclasses must implement this to take care of loading their data, as per startLoading. This is not called by clients directly, but as a result of a call to startLoading. This will always be called from the process's main thread.
onStopLoading
@MainThread
protected void onStopLoading()
Subclasses must implement this to take care of stopping their loader, as per stopLoading. This is not called by clients directly, but as a result of a call to stopLoading. This will always be called from the process's main thread.