michael@0: /*
michael@0:  * This is an adapted version of Android's original CursorLoader
michael@0:  * without all the ContentProvider-specific bits.
michael@0:  *
michael@0:  * Copyright (C) 2011 The Android Open Source Project
michael@0:  *
michael@0:  * Licensed under the Apache License, Version 2.0 (the "License");
michael@0:  * you may not use this file except in compliance with the License.
michael@0:  * You may obtain a copy of the License at
michael@0:  *
michael@0:  *      http://www.apache.org/licenses/LICENSE-2.0
michael@0:  *
michael@0:  * Unless required by applicable law or agreed to in writing, software
michael@0:  * distributed under the License is distributed on an "AS IS" BASIS,
michael@0:  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
michael@0:  * See the License for the specific language governing permissions and
michael@0:  * limitations under the License.
michael@0:  */
michael@0: 
michael@0: package org.mozilla.gecko.home;
michael@0: 
michael@0: import android.content.Context;
michael@0: import android.database.Cursor;
michael@0: import android.support.v4.content.AsyncTaskLoader;
michael@0: 
michael@0: abstract class SimpleCursorLoader extends AsyncTaskLoader<Cursor> {
michael@0:     final ForceLoadContentObserver mObserver;
michael@0:     Cursor mCursor;
michael@0: 
michael@0:     public SimpleCursorLoader(Context context) {
michael@0:         super(context);
michael@0:         mObserver = new ForceLoadContentObserver();
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Loads the target cursor for this loader. This method is called
michael@0:      * on a worker thread.
michael@0:      */
michael@0:     protected abstract Cursor loadCursor();
michael@0: 
michael@0:     /* Runs on a worker thread */
michael@0:     @Override
michael@0:     public Cursor loadInBackground() {
michael@0:         Cursor cursor = loadCursor();
michael@0: 
michael@0:         if (cursor != null) {
michael@0:             // Ensure the cursor window is filled
michael@0:             cursor.getCount();
michael@0:             cursor.registerContentObserver(mObserver);
michael@0:         }
michael@0: 
michael@0:         return cursor;
michael@0:     }
michael@0: 
michael@0:     /* Runs on the UI thread */
michael@0:     @Override
michael@0:     public void deliverResult(Cursor cursor) {
michael@0:         if (isReset()) {
michael@0:             // An async query came in while the loader is stopped
michael@0:             if (cursor != null) {
michael@0:                 cursor.close();
michael@0:             }
michael@0: 
michael@0:             return;
michael@0:         }
michael@0: 
michael@0:         Cursor oldCursor = mCursor;
michael@0:         mCursor = cursor;
michael@0: 
michael@0:         if (isStarted()) {
michael@0:             super.deliverResult(cursor);
michael@0:         }
michael@0: 
michael@0:         if (oldCursor != null && oldCursor != cursor && !oldCursor.isClosed()) {
michael@0:             oldCursor.close();
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Starts an asynchronous load of the list data. When the result is ready the callbacks
michael@0:      * will be called on the UI thread. If a previous load has been completed and is still valid
michael@0:      * the result may be passed to the callbacks immediately.
michael@0:      *
michael@0:      * Must be called from the UI thread
michael@0:      */
michael@0:     @Override
michael@0:     protected void onStartLoading() {
michael@0:         if (mCursor != null) {
michael@0:             deliverResult(mCursor);
michael@0:         }
michael@0: 
michael@0:         if (takeContentChanged() || mCursor == null) {
michael@0:             forceLoad();
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Must be called from the UI thread
michael@0:      */
michael@0:     @Override
michael@0:     protected void onStopLoading() {
michael@0:         // Attempt to cancel the current load task if possible.
michael@0:         cancelLoad();
michael@0:     }
michael@0: 
michael@0:     @Override
michael@0:     public void onCanceled(Cursor cursor) {
michael@0:         if (cursor != null && !cursor.isClosed()) {
michael@0:             cursor.close();
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     @Override
michael@0:     protected void onReset() {
michael@0:         super.onReset();
michael@0: 
michael@0:         // Ensure the loader is stopped
michael@0:         onStopLoading();
michael@0: 
michael@0:         if (mCursor != null && !mCursor.isClosed()) {
michael@0:             mCursor.close();
michael@0:         }
michael@0: 
michael@0:         mCursor = null;
michael@0:     }
michael@0: }