| /* |
| * Copyright (C) 2010 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package android.content; |
| |
| import android.database.ContentObserver; |
| import android.os.Handler; |
| import android.util.DebugUtils; |
| |
| import java.io.FileDescriptor; |
| import java.io.PrintWriter; |
| |
| /** |
| * A class that performs asynchronous loading of data. While Loaders are active |
| * they should monitor the source of their data and deliver new results when the contents |
| * change. See {@link android.app.LoaderManager} for more detail. |
| * |
| * <p><b>Note on threading:</b> Clients of loaders should as a rule perform |
| * any calls on to a Loader from the main thread of their process (that is, |
| * the thread the Activity callbacks and other things occur on). Subclasses |
| * of Loader (such as {@link AsyncTaskLoader}) will often perform their work |
| * in a separate thread, but when delivering their results this too should |
| * be done on the main thread.</p> |
| * |
| * <p>Subclasses generally must implement at least {@link #onStartLoading()}, |
| * {@link #onStopLoading()}, {@link #onForceLoad()}, and {@link #onReset()}.</p> |
| * |
| * <p>Most implementations should not derive directly from this class, but |
| * instead inherit from {@link AsyncTaskLoader}.</p> |
| * |
| * <div class="special reference"> |
| * <h3>Developer Guides</h3> |
| * <p>For more information about using loaders, read the |
| * <a href="{@docRoot}guide/components/loaders.html">Loaders</a> developer guide.</p> |
| * </div> |
| * |
| * @param <D> The result returned when the load is complete |
| * |
| * @deprecated Use the <a href="{@docRoot}tools/extras/support-library.html">Support Library</a> |
| * {@link android.support.v4.content.Loader} |
| */ |
| @Deprecated |
| public class Loader<D> { |
| int mId; |
| OnLoadCompleteListener<D> mListener; |
| OnLoadCanceledListener<D> mOnLoadCanceledListener; |
| Context mContext; |
| boolean mStarted = false; |
| boolean mAbandoned = false; |
| boolean mReset = true; |
| boolean mContentChanged = false; |
| boolean mProcessingChange = false; |
| |
| /** |
| * An 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. You do not normally need to use this yourself; |
| * it is used for you by {@link CursorLoader} to take care of executing |
| * an update when the cursor's backing data changes. |
| * |
| * @deprecated Use {@link android.support.v4.content.Loader.ForceLoadContentObserver} |
| */ |
| @Deprecated |
| public final class ForceLoadContentObserver extends ContentObserver { |
| public ForceLoadContentObserver() { |
| super(new Handler()); |
| } |
| |
| @Override |
| public boolean deliverSelfNotifications() { |
| return true; |
| } |
| |
| @Override |
| public void onChange(boolean selfChange) { |
| onContentChanged(); |
| } |
| } |
| |
| /** |
| * Interface that is implemented to discover when a Loader has finished |
| * loading its data. You do not normally need to implement this yourself; |
| * it is used in the implementation of {@link android.app.LoaderManager} |
| * to find out when a Loader it is managing has completed so that this can |
| * be reported to its client. This interface should only be used if a |
| * Loader is not being used in conjunction with LoaderManager. |
| * |
| * @deprecated Use {@link android.support.v4.content.Loader.OnLoadCompleteListener} |
| */ |
| @Deprecated |
| public interface OnLoadCompleteListener<D> { |
| /** |
| * Called on the thread that created the Loader when the load is complete. |
| * |
| * @param loader the loader that completed the load |
| * @param data the result of the load |
| */ |
| public void onLoadComplete(Loader<D> loader, D data); |
| } |
| |
| /** |
| * Interface that is implemented to discover when a Loader has been canceled |
| * before it finished loading its data. You do not normally need to implement |
| * this yourself; it is used in the implementation of {@link android.app.LoaderManager} |
| * to find out when a Loader it is managing has been canceled so that it |
| * can schedule the next Loader. This interface should only be used if a |
| * Loader is not being used in conjunction with LoaderManager. |
| * |
| * @deprecated Use {@link android.support.v4.content.Loader.OnLoadCanceledListener} |
| */ |
| @Deprecated |
| public interface OnLoadCanceledListener<D> { |
| /** |
| * Called on the thread that created the Loader when the load is canceled. |
| * |
| * @param loader the loader that canceled the load |
| */ |
| public void onLoadCanceled(Loader<D> loader); |
| } |
| |
| /** |
| * 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 {@link #getContext()} to retrieve |
| * the Loader's Context, don't use the constructor argument directly. |
| * The Context returned by {@link #getContext} is safe to use across |
| * Activity instances. |
| * |
| * @param context used to retrieve the application context. |
| */ |
| public Loader(Context context) { |
| mContext = context.getApplicationContext(); |
| } |
| |
| /** |
| * 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. |
| * |
| * @param data the result of the load |
| */ |
| public void deliverResult(D data) { |
| if (mListener != null) { |
| mListener.onLoadComplete(this, data); |
| } |
| } |
| |
| /** |
| * Informs the registered {@link OnLoadCanceledListener} that the load has been canceled. |
| * Should only be called by subclasses. |
| * |
| * Must be called from the process's main thread. |
| */ |
| public void deliverCancellation() { |
| if (mOnLoadCanceledListener != null) { |
| mOnLoadCanceledListener.onLoadCanceled(this); |
| } |
| } |
| |
| /** |
| * @return an application context retrieved from the Context passed to the constructor. |
| */ |
| public Context getContext() { |
| return mContext; |
| } |
| |
| /** |
| * @return the ID of this loader |
| */ |
| public int getId() { |
| return mId; |
| } |
| |
| /** |
| * 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. |
| * |
| * <p>Must be called from the process's main thread. |
| */ |
| public void registerListener(int id, OnLoadCompleteListener<D> listener) { |
| if (mListener != null) { |
| throw new IllegalStateException("There is already a listener registered"); |
| } |
| mListener = listener; |
| mId = id; |
| } |
| |
| /** |
| * Remove a listener that was previously added with {@link #registerListener}. |
| * |
| * Must be called from the process's main thread. |
| */ |
| public void unregisterListener(OnLoadCompleteListener<D> listener) { |
| if (mListener == null) { |
| throw new IllegalStateException("No listener register"); |
| } |
| if (mListener != listener) { |
| throw new IllegalArgumentException("Attempting to unregister the wrong listener"); |
| } |
| mListener = null; |
| } |
| |
| /** |
| * 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. |
| * |
| * @param listener The listener to register. |
| */ |
| public void registerOnLoadCanceledListener(OnLoadCanceledListener<D> listener) { |
| if (mOnLoadCanceledListener != null) { |
| throw new IllegalStateException("There is already a listener registered"); |
| } |
| mOnLoadCanceledListener = listener; |
| } |
| |
| /** |
| * Unregisters a listener that was previously added with |
| * {@link #registerOnLoadCanceledListener}. |
| * |
| * Must be called from the process's main thread. |
| * |
| * @param listener The listener to unregister. |
| */ |
| public void unregisterOnLoadCanceledListener(OnLoadCanceledListener<D> listener) { |
| if (mOnLoadCanceledListener == null) { |
| throw new IllegalStateException("No listener register"); |
| } |
| if (mOnLoadCanceledListener != listener) { |
| throw new IllegalArgumentException("Attempting to unregister the wrong listener"); |
| } |
| mOnLoadCanceledListener = null; |
| } |
| |
| /** |
| * Return whether this load has been started. That is, its {@link #startLoading()} |
| * has been called and no calls to {@link #stopLoading()} or |
| * {@link #reset()} have yet been made. |
| */ |
| public boolean isStarted() { |
| return mStarted; |
| } |
| |
| /** |
| * Return whether this loader has been abandoned. In this state, the |
| * loader <em>must not</em> report any new data, and <em>must</em> keep |
| * its last reported data valid until it is finally reset. |
| */ |
| public boolean isAbandoned() { |
| return mAbandoned; |
| } |
| |
| /** |
| * Return whether this load has been reset. That is, either the loader |
| * has not yet been started for the first time, or its {@link #reset()} |
| * has been called. |
| */ |
| public boolean isReset() { |
| return mReset; |
| } |
| |
| /** |
| * This function will normally be called for you automatically by |
| * {@link android.app.LoaderManager} when the associated fragment/activity |
| * is being started. When using a Loader with {@link android.app.LoaderManager}, |
| * you <em>must not</em> 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 {@link #stopLoading} will stop the delivery of callbacks. |
| * |
| * <p>This updates the Loader's internal state so that |
| * {@link #isStarted()} and {@link #isReset()} will return the correct |
| * values, and then calls the implementation's {@link #onStartLoading()}. |
| * |
| * <p>Must be called from the process's main thread. |
| */ |
| public final void startLoading() { |
| mStarted = true; |
| mReset = false; |
| mAbandoned = false; |
| onStartLoading(); |
| } |
| |
| /** |
| * Subclasses must implement this to take care of loading their data, |
| * as per {@link #startLoading()}. This is not called by clients directly, |
| * but as a result of a call to {@link #startLoading()}. |
| */ |
| protected void onStartLoading() { |
| } |
| |
| /** |
| * Attempt to cancel the current load task. |
| * Must be called on the main thread of the process. |
| * |
| * <p>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. |
| * |
| * @return Returns <tt>false</tt> if the task could not be canceled, |
| * typically because it has already completed normally, or |
| * because {@link #startLoading()} hasn't been called; returns |
| * <tt>true</tt> otherwise. When <tt>true</tt> is returned, the task |
| * is still running and the {@link OnLoadCanceledListener} will be called |
| * when the task completes. |
| */ |
| public boolean cancelLoad() { |
| return onCancelLoad(); |
| } |
| |
| /** |
| * Subclasses must implement this to take care of requests to {@link #cancelLoad()}. |
| * This will always be called from the process's main thread. |
| * |
| * @return Returns <tt>false</tt> if the task could not be canceled, |
| * typically because it has already completed normally, or |
| * because {@link #startLoading()} hasn't been called; returns |
| * <tt>true</tt> otherwise. When <tt>true</tt> is returned, the task |
| * is still running and the {@link OnLoadCanceledListener} will be called |
| * when the task completes. |
| */ |
| protected boolean onCancelLoad() { |
| return false; |
| } |
| |
| /** |
| * Force an asynchronous load. Unlike {@link #startLoading()} this will ignore a previously |
| * loaded data set and load a new one. This simply calls through to the |
| * implementation's {@link #onForceLoad()}. You generally should only call this |
| * when the loader is started -- that is, {@link #isStarted()} returns true. |
| * |
| * <p>Must be called from the process's main thread. |
| */ |
| public void forceLoad() { |
| onForceLoad(); |
| } |
| |
| /** |
| * Subclasses must implement this to take care of requests to {@link #forceLoad()}. |
| * This will always be called from the process's main thread. |
| */ |
| protected void onForceLoad() { |
| } |
| |
| /** |
| * This function will normally be called for you automatically by |
| * {@link android.app.LoaderManager} when the associated fragment/activity |
| * is being stopped. When using a Loader with {@link android.app.LoaderManager}, |
| * you <em>must not</em> call this method yourself, or you will conflict |
| * with its management of the Loader. |
| * |
| * <p>Stops delivery of updates until the next time {@link #startLoading()} is called. |
| * Implementations should <em>not</em> 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 {@link #startLoading()} is later called. |
| * |
| * <p>This updates the Loader's internal state so that |
| * {@link #isStarted()} will return the correct |
| * value, and then calls the implementation's {@link #onStopLoading()}. |
| * |
| * <p>Must be called from the process's main thread. |
| */ |
| public void stopLoading() { |
| mStarted = false; |
| onStopLoading(); |
| } |
| |
| /** |
| * Subclasses must implement this to take care of stopping their loader, |
| * as per {@link #stopLoading()}. This is not called by clients directly, |
| * but as a result of a call to {@link #stopLoading()}. |
| * This will always be called from the process's main thread. |
| */ |
| protected void onStopLoading() { |
| } |
| |
| /** |
| * This function will normally be called for you automatically by |
| * {@link android.app.LoaderManager} when restarting a Loader. When using |
| * a Loader with {@link android.app.LoaderManager}, |
| * you <em>must not</em> 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 {@link #reset} to have it retain its current data but not report |
| * any new data. |
| */ |
| public void abandon() { |
| mAbandoned = true; |
| onAbandon(); |
| } |
| |
| /** |
| * Subclasses implement this to take care of being abandoned. This is |
| * an optional intermediate state prior to {@link #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 <em>must</em> keep its last reported data valid until the final |
| * {@link #onReset()} happens. You can retrieve the current abandoned |
| * state with {@link #isAbandoned}. |
| */ |
| protected void onAbandon() { |
| } |
| |
| /** |
| * This function will normally be called for you automatically by |
| * {@link android.app.LoaderManager} when destroying a Loader. When using |
| * a Loader with {@link android.app.LoaderManager}, |
| * you <em>must not</em> 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 |
| * {@link #startLoading()} may later be called at which point it must be |
| * able to start running again. |
| * |
| * <p>This updates the Loader's internal state so that |
| * {@link #isStarted()} and {@link #isReset()} will return the correct |
| * values, and then calls the implementation's {@link #onReset()}. |
| * |
| * <p>Must be called from the process's main thread. |
| */ |
| public void reset() { |
| onReset(); |
| mReset = true; |
| mStarted = false; |
| mAbandoned = false; |
| mContentChanged = false; |
| mProcessingChange = false; |
| } |
| |
| /** |
| * Subclasses must implement this to take care of resetting their loader, |
| * as per {@link #reset()}. This is not called by clients directly, |
| * but as a result of a call to {@link #reset()}. |
| * This will always be called from the process's main thread. |
| */ |
| protected void onReset() { |
| } |
| |
| /** |
| * 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. |
| */ |
| public boolean takeContentChanged() { |
| boolean res = mContentChanged; |
| mContentChanged = false; |
| mProcessingChange |= res; |
| return res; |
| } |
| |
| /** |
| * Commit that you have actually fully processed a content change that |
| * was returned by {@link #takeContentChanged}. This is for use with |
| * {@link #rollbackContentChanged()} to handle situations where a load |
| * is cancelled. Call this when you have completely processed a load |
| * without it being cancelled. |
| */ |
| public void commitContentChanged() { |
| mProcessingChange = false; |
| } |
| |
| /** |
| * Report that you have abandoned the processing of a content change that |
| * was returned by {@link #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. |
| */ |
| public void rollbackContentChanged() { |
| if (mProcessingChange) { |
| onContentChanged(); |
| } |
| } |
| |
| /** |
| * Called when {@link ForceLoadContentObserver} detects a change. The |
| * default implementation checks to see if the loader is currently started; |
| * if so, it simply calls {@link #forceLoad()}; otherwise, it sets a flag |
| * so that {@link #takeContentChanged()} returns true. |
| * |
| * <p>Must be called from the process's main thread. |
| */ |
| public void onContentChanged() { |
| if (mStarted) { |
| forceLoad(); |
| } else { |
| // This loader has been stopped, so we don't want to load |
| // new data right now... but keep track of it changing to |
| // refresh later if we start again. |
| mContentChanged = true; |
| } |
| } |
| |
| /** |
| * For debugging, converts an instance of the Loader's data class to |
| * a string that can be printed. Must handle a null data. |
| */ |
| public String dataToString(D data) { |
| StringBuilder sb = new StringBuilder(64); |
| DebugUtils.buildShortClassTag(data, sb); |
| sb.append("}"); |
| return sb.toString(); |
| } |
| |
| @Override |
| public String toString() { |
| StringBuilder sb = new StringBuilder(64); |
| DebugUtils.buildShortClassTag(this, sb); |
| sb.append(" id="); |
| sb.append(mId); |
| sb.append("}"); |
| return sb.toString(); |
| } |
| |
| /** |
| * Print the Loader's state into the given stream. |
| * |
| * @param prefix Text to print at the front of each line. |
| * @param fd The raw file descriptor that the dump is being sent to. |
| * @param writer A PrintWriter to which the dump is to be set. |
| * @param args Additional arguments to the dump request. |
| */ |
| public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) { |
| writer.print(prefix); writer.print("mId="); writer.print(mId); |
| writer.print(" mListener="); writer.println(mListener); |
| if (mStarted || mContentChanged || mProcessingChange) { |
| writer.print(prefix); writer.print("mStarted="); writer.print(mStarted); |
| writer.print(" mContentChanged="); writer.print(mContentChanged); |
| writer.print(" mProcessingChange="); writer.println(mProcessingChange); |
| } |
| if (mAbandoned || mReset) { |
| writer.print(prefix); writer.print("mAbandoned="); writer.print(mAbandoned); |
| writer.print(" mReset="); writer.println(mReset); |
| } |
| } |
| } |
