src/com/android/gallery3d/app/TimeLineDataLoader.java - platform/packages/apps/Gallery2 - Gitiles

 /*
  * 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 com.android.gallery3d.app;

 import android.os.Handler;
 import android.os.Message;
 import android.os.Process;

 import com.android.gallery3d.common.Utils;
 import com.android.gallery3d.data.ContentListener;
 import com.android.gallery3d.data.MediaItem;
 import com.android.gallery3d.data.MediaObject;
 import com.android.gallery3d.data.MediaSet;
 import com.android.gallery3d.data.Path;
 import com.android.gallery3d.data.ClusterAlbumSet;
 import com.android.gallery3d.ui.SynchronizedHandler;

 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.FutureTask;

 public class TimeLineDataLoader {
     @SuppressWarnings("unused")
     private static final String TAG = "TimeLineDataLoader";
     private static final int DATA_CACHE_SIZE = 96 * 2;

     private static final int MSG_LOAD_START = 1;
     private static final int MSG_LOAD_FINISH = 2;
     private static final int MSG_RUN_OBJECT = 3;

     private static final int MIN_LOAD_COUNT = 32;
     private static final int MAX_LOAD_COUNT = 96 * 2;

     private final MediaItem[] mData;
     private final long[] mItemVersion;
     private final long[] mSetVersion;

     public static interface DataListener {
         public void onContentChanged(int index);
         public void onSizeChanged();
     }

     private int mActiveStart = 0;
     private int mActiveEnd = 0;

     private int mContentStart = 0;
     private int mContentEnd = 0;

     private final MediaSet mSource;
     private long mSourceVersion = MediaObject.INVALID_DATA_VERSION;

     private final Handler mMainHandler;
     private int mSize = 0;

     private ArrayList<DataListener> mDataListener = new ArrayList<>();
     private MySourceListener mSourceListener = new MySourceListener();
     private LoadingListener mLoadingListener;

     private ReloadTask mReloadTask;
     // the data version on which last loading failed
     private long mFailedVersion = MediaObject.INVALID_DATA_VERSION;

     public TimeLineDataLoader(AbstractGalleryActivity context, MediaSet mediaSet) {
         mSource = mediaSet;
         mData = new MediaItem[DATA_CACHE_SIZE];
         mItemVersion = new long[DATA_CACHE_SIZE];
         mSetVersion = new long[DATA_CACHE_SIZE];
         Arrays.fill(mItemVersion, MediaObject.INVALID_DATA_VERSION);
         Arrays.fill(mSetVersion, MediaObject.INVALID_DATA_VERSION);

         mMainHandler = new SynchronizedHandler(context.getGLRoot()) {
             @Override
             public void handleMessage(Message message) {
                 switch (message.what) {
                     case MSG_RUN_OBJECT:
                         ((Runnable) message.obj).run();
                         return;
                     case MSG_LOAD_START:
                         if (mLoadingListener != null) mLoadingListener.onLoadingStarted();
                         return;
                     case MSG_LOAD_FINISH:
                         if (mLoadingListener != null) {
                             boolean loadingFailed =
                                     (mFailedVersion != MediaObject.INVALID_DATA_VERSION);
                             mLoadingListener.onLoadingFinished(loadingFailed);
                         }
                         return;
                 }
             }
         };
     }

     public void resume() {
         mSource.addContentListener(mSourceListener);
         mReloadTask = new ReloadTask();
         mReloadTask.start();
     }

     public void pause() {
         mReloadTask.terminate();
         mReloadTask = null;
         mSource.removeContentListener(mSourceListener);
     }

     public MediaSet getMediaSet(int index) {
         return ((ClusterAlbumSet) mSource).getAlbumFromindex(index);
     }

     public MediaItem get(int index) {
         if (!isActive(index)) {
             ArrayList<MediaItem> items = mSource.getMediaItem(index, 1);
             if (items != null && items.size() > 0) {
                 return items.get(0);
             }
         }
         return mData[index % mData.length];
     }

     public int getTimeLineTitlesCount() {
         return mSource.getSubMediaSetCount();
     }

     public boolean isActive(int index) {
         return index >= mActiveStart && index < mActiveEnd;
     }

     public int size() {
         return mSize;
     }

     public int[] getSubMediaSetCount() {
         ClusterAlbumSet set = (ClusterAlbumSet) mSource;
         int albumCount = set.getSubMediaSetCount();
         int[] counts = new int[albumCount];
         for (int i = albumCount - 1; i >= 0; --i) {
             counts[i] = set.getSubMediaSet(i).getSelectableItemCount();
         }
         return counts;
     }

     // Returns the index of the MediaItem with the given path or
     // -1 if the path is not cached
     public int findItem(Path id) {
         return getIndex(id, true);
     }

     /**
      * @param id            given path
      * @param needTitleItem timeline title items will be filtered out if true.
      * @return the index of the MediaItem with the given path or -1 if the path is not cached.
      */
     public int getIndex(Path id, final boolean needTitleItem) {
         for (int i = mContentStart, offset = 0; i < mContentEnd; i++) {
             MediaItem item = mData[i % DATA_CACHE_SIZE];
             if (item != null) {
                 if (!needTitleItem && !item.isSelectable()) {
                     offset++;
                 } else if (id == item.getPath()) {
                     return i - offset;
                 }
             }
         }
         return -1;
     }

     private void clearSlot(int slotIndex) {
         mData[slotIndex] = null;
         mItemVersion[slotIndex] = MediaObject.INVALID_DATA_VERSION;
         mSetVersion[slotIndex] = MediaObject.INVALID_DATA_VERSION;
     }

     private void setContentWindow(int contentStart, int contentEnd) {
         if (contentStart == mContentStart && contentEnd == mContentEnd) return;
         int end = mContentEnd;
         int start = mContentStart;

         // We need change the content window before calling reloadData(...)
         synchronized (this) {
             mContentStart = contentStart;
             mContentEnd = contentEnd;
         }
         if (contentStart >= end || start >= contentEnd) {
             for (int i = start, n = end; i < n; ++i) {
                 clearSlot(i % DATA_CACHE_SIZE);
             }
         } else {
             for (int i = start; i < contentStart; ++i) {
                 clearSlot(i % DATA_CACHE_SIZE);
             }
             for (int i = contentEnd, n = end; i < n; ++i) {
                 clearSlot(i % DATA_CACHE_SIZE);
             }
         }
         if (mReloadTask != null) mReloadTask.notifyDirty();
     }

     public void setActiveWindow(int start, int end) {
         if (start == mActiveStart && end == mActiveEnd) return;

         Utils.assertTrue(start <= end
                 && end - start <= mData.length && end <= mSize);

         int length = mData.length;
         mActiveStart = start;
         mActiveEnd = end;

         // If no data is visible, keep the cache content
         if (start == end) return;

         int contentStart = Utils.clamp((start + end) / 2 - length / 2,
                 0, Math.max(0, mSize - length));
         int contentEnd = Math.min(contentStart + length, mSize);
         if (mContentStart > start || mContentEnd < end
                 || Math.abs(contentStart - mContentStart) > MIN_LOAD_COUNT) {
             setContentWindow(contentStart, contentEnd);
         }
     }

     private class MySourceListener implements ContentListener {
         @Override
         public void onContentDirty() {
             if (mReloadTask != null) mReloadTask.notifyDirty();
         }
     }

     public void setDataListener(DataListener listener) {
         mDataListener.add(listener);
     }

     public void removeDataListener(DataListener listener) {
         mDataListener.remove(listener);
     }

     public void setLoadingListener(LoadingListener listener) {
         mLoadingListener = listener;
     }

     private <T> T executeAndWait(Callable<T> callable) {
         FutureTask<T> task = new FutureTask<T>(callable);
         mMainHandler.sendMessage(
                 mMainHandler.obtainMessage(MSG_RUN_OBJECT, task));
         try {
             return task.get();
         } catch (InterruptedException e) {
             return null;
         } catch (ExecutionException e) {
             throw new RuntimeException(e);
         }
     }

     private static class UpdateInfo {
         public long version;
         public int reloadStart;
         public int reloadCount;

         public int size;
         public ArrayList<MediaItem> items;
     }

     private class GetUpdateInfo implements Callable<UpdateInfo> {
         private final long mVersion;

         public GetUpdateInfo(long version) {
             mVersion = version;
         }

         @Override
         public UpdateInfo call() throws Exception {
             if (mFailedVersion == mVersion) {
                 // previous loading failed, return null to pause loading
                 return null;
             }
             UpdateInfo info = new UpdateInfo();
             long version = mVersion;
             info.version = mSourceVersion;
             info.size = mSize;
             long setVersion[] = mSetVersion;
             for (int i = mContentStart, n = mContentEnd; i < n; ++i) {
                 int index = i % DATA_CACHE_SIZE;
                 if (setVersion[index] != version) {
                     info.reloadStart = i;
                     info.reloadCount = Math.min(MAX_LOAD_COUNT, n - i);
                     return info;
                 }
             }
             return mSourceVersion == mVersion ? null : info;
         }
     }

     private class UpdateContent implements Callable<Void> {

         private UpdateInfo mUpdateInfo;

         public UpdateContent(UpdateInfo info) {
             mUpdateInfo = info;
         }

         @Override
         public Void call() throws Exception {
             UpdateInfo info = mUpdateInfo;
             mSourceVersion = info.version;
             if (mSize != info.size) {
                 mSize = info.size;
                 if (mDataListener != null)
                     for (DataListener l : mDataListener) {
                         l.onSizeChanged();
                     }
                 if (mContentEnd > mSize) mContentEnd = mSize;
                 if (mActiveEnd > mSize) mActiveEnd = mSize;
             }

             ArrayList<MediaItem> items = info.items;

             mFailedVersion = MediaObject.INVALID_DATA_VERSION;
             if ((items == null) || items.isEmpty()) {
                 if (info.reloadCount > 0) {
                     mFailedVersion = info.version;
                     Log.d(TAG, "loading failed: " + mFailedVersion);
                 }
                 return null;
             }
             int start = Math.max(info.reloadStart, mContentStart);
             int end = Math.min(info.reloadStart + items.size(), mContentEnd);

             for (int i = start; i < end; ++i) {
                 int index = i % DATA_CACHE_SIZE;
                 mSetVersion[index] = info.version;
                 MediaItem updateItem = items.get(i - info.reloadStart);
                 if (updateItem != null) {
                     long itemVersion = updateItem.getDataVersion();
                     if (mItemVersion[index] != itemVersion) {
                         mItemVersion[index] = itemVersion;
                         mData[index] = updateItem;
                         if (mDataListener != null && i >= mActiveStart && i < mActiveEnd) {
                             for (DataListener l : mDataListener) {
                                 l.onContentChanged(i);
                             }
                         }
                     }
                }
             }
             return null;
         }
     }

     /*
      * The thread model of ReloadTask
      *      *
      * [Reload Task]       [Main Thread]
      *       |                   |
      * getUpdateInfo() -->       |           (synchronous call)
      *     (wait) <----    getUpdateInfo()
      *       |                   |
      *   Load Data               |
      *       |                   |
      * updateContent() -->       |           (synchronous call)
      *     (wait)          updateContent()
      *       |                   |
      *       |                   |
      */
     private class ReloadTask extends Thread {

         private volatile boolean mActive = true;
         private volatile boolean mDirty = true;
         private boolean mIsLoading = false;

         private void updateLoading(boolean loading) {
             if (mIsLoading == loading) return;
             mIsLoading = loading;
             mMainHandler.sendEmptyMessage(loading ? MSG_LOAD_START : MSG_LOAD_FINISH);
         }

         @Override
         public void run() {
             Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
             boolean updateComplete = false;
             long version = MediaObject.INVALID_DATA_VERSION;
             while (mActive) {
                 synchronized (this) {
                     if (mActive && !mDirty && updateComplete
                             && version != MediaObject.INVALID_DATA_VERSION) {
                         updateLoading(false);
                         Utils.waitWithoutInterrupt(this);
                         continue;
                     }
                     mDirty = false;
                 }
                 updateLoading(true);
                 version = mSource.reload();
                 UpdateInfo info = executeAndWait(new GetUpdateInfo(version));
                 updateComplete = info == null;
                 if (updateComplete) {
                     continue;
                 }
                 if (info.version != version) {
                     info.size = mSource.getMediaItemCount();
                     info.version = version;
                 }
                 if (info.reloadCount > 0) {
                     int start = Math.max(info.reloadStart, mContentStart);
                     int end = Math.min(info.reloadStart + info.reloadCount, mContentEnd);
                     info.items = mSource.getMediaItem(start, end - start);
                 }
                 executeAndWait(new UpdateContent(info));
             }
             updateLoading(false);
         }

         public synchronized void notifyDirty() {
             mDirty = true;
             notifyAll();
         }

         public synchronized void terminate() {
             mActive = false;
             notifyAll();
         }
     }
 }
	/*
	* 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 com.android.gallery3d.app;

	import android.os.Handler;
	import android.os.Message;
	import android.os.Process;

	import com.android.gallery3d.common.Utils;
	import com.android.gallery3d.data.ContentListener;
	import com.android.gallery3d.data.MediaItem;
	import com.android.gallery3d.data.MediaObject;
	import com.android.gallery3d.data.MediaSet;
	import com.android.gallery3d.data.Path;
	import com.android.gallery3d.data.ClusterAlbumSet;
	import com.android.gallery3d.ui.SynchronizedHandler;

	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.concurrent.Callable;
	import java.util.concurrent.ExecutionException;
	import java.util.concurrent.FutureTask;

	public class TimeLineDataLoader {
	@SuppressWarnings("unused")
	private static final String TAG = "TimeLineDataLoader";
	private static final int DATA_CACHE_SIZE = 96 * 2;

	private static final int MSG_LOAD_START = 1;
	private static final int MSG_LOAD_FINISH = 2;
	private static final int MSG_RUN_OBJECT = 3;

	private static final int MIN_LOAD_COUNT = 32;
	private static final int MAX_LOAD_COUNT = 96 * 2;

	private final MediaItem[] mData;
	private final long[] mItemVersion;
	private final long[] mSetVersion;

	public static interface DataListener {
	public void onContentChanged(int index);
	public void onSizeChanged();
	}

	private int mActiveStart = 0;
	private int mActiveEnd = 0;

	private int mContentStart = 0;
	private int mContentEnd = 0;

	private final MediaSet mSource;
	private long mSourceVersion = MediaObject.INVALID_DATA_VERSION;

	private final Handler mMainHandler;
	private int mSize = 0;

	private ArrayList<DataListener> mDataListener = new ArrayList<>();
	private MySourceListener mSourceListener = new MySourceListener();
	private LoadingListener mLoadingListener;

	private ReloadTask mReloadTask;
	// the data version on which last loading failed
	private long mFailedVersion = MediaObject.INVALID_DATA_VERSION;

	public TimeLineDataLoader(AbstractGalleryActivity context, MediaSet mediaSet) {
	mSource = mediaSet;
	mData = new MediaItem[DATA_CACHE_SIZE];
	mItemVersion = new long[DATA_CACHE_SIZE];
	mSetVersion = new long[DATA_CACHE_SIZE];
	Arrays.fill(mItemVersion, MediaObject.INVALID_DATA_VERSION);
	Arrays.fill(mSetVersion, MediaObject.INVALID_DATA_VERSION);

	mMainHandler = new SynchronizedHandler(context.getGLRoot()) {
	@Override
	public void handleMessage(Message message) {
	switch (message.what) {
	case MSG_RUN_OBJECT:
	((Runnable) message.obj).run();
	return;
	case MSG_LOAD_START:
	if (mLoadingListener != null) mLoadingListener.onLoadingStarted();
	return;
	case MSG_LOAD_FINISH:
	if (mLoadingListener != null) {
	boolean loadingFailed =
	(mFailedVersion != MediaObject.INVALID_DATA_VERSION);
	mLoadingListener.onLoadingFinished(loadingFailed);
	}
	return;
	}
	}
	};
	}

	public void resume() {
	mSource.addContentListener(mSourceListener);
	mReloadTask = new ReloadTask();
	mReloadTask.start();
	}

	public void pause() {
	mReloadTask.terminate();
	mReloadTask = null;
	mSource.removeContentListener(mSourceListener);
	}

	public MediaSet getMediaSet(int index) {
	return ((ClusterAlbumSet) mSource).getAlbumFromindex(index);
	}

	public MediaItem get(int index) {
	if (!isActive(index)) {
	ArrayList<MediaItem> items = mSource.getMediaItem(index, 1);
	if (items != null && items.size() > 0) {
	return items.get(0);
	}
	}
	return mData[index % mData.length];
	}

	public int getTimeLineTitlesCount() {
	return mSource.getSubMediaSetCount();
	}

	public boolean isActive(int index) {
	return index >= mActiveStart && index < mActiveEnd;
	}

	public int size() {
	return mSize;
	}

	public int[] getSubMediaSetCount() {
	ClusterAlbumSet set = (ClusterAlbumSet) mSource;
	int albumCount = set.getSubMediaSetCount();
	int[] counts = new int[albumCount];
	for (int i = albumCount - 1; i >= 0; --i) {
	counts[i] = set.getSubMediaSet(i).getSelectableItemCount();
	}
	return counts;
	}

	// Returns the index of the MediaItem with the given path or
	// -1 if the path is not cached
	public int findItem(Path id) {
	return getIndex(id, true);
	}

	/**
	* @param id given path
	* @param needTitleItem timeline title items will be filtered out if true.
	* @return the index of the MediaItem with the given path or -1 if the path is not cached.
	*/
	public int getIndex(Path id, final boolean needTitleItem) {
	for (int i = mContentStart, offset = 0; i < mContentEnd; i++) {
	MediaItem item = mData[i % DATA_CACHE_SIZE];
	if (item != null) {
	if (!needTitleItem && !item.isSelectable()) {
	offset++;
	} else if (id == item.getPath()) {
	return i - offset;
	}
	}
	}
	return -1;
	}

	private void clearSlot(int slotIndex) {
	mData[slotIndex] = null;
	mItemVersion[slotIndex] = MediaObject.INVALID_DATA_VERSION;
	mSetVersion[slotIndex] = MediaObject.INVALID_DATA_VERSION;
	}

	private void setContentWindow(int contentStart, int contentEnd) {
	if (contentStart == mContentStart && contentEnd == mContentEnd) return;
	int end = mContentEnd;
	int start = mContentStart;

	// We need change the content window before calling reloadData(...)
	synchronized (this) {
	mContentStart = contentStart;
	mContentEnd = contentEnd;
	}
	if (contentStart >= end \|\| start >= contentEnd) {
	for (int i = start, n = end; i < n; ++i) {
	clearSlot(i % DATA_CACHE_SIZE);
	}
	} else {
	for (int i = start; i < contentStart; ++i) {
	clearSlot(i % DATA_CACHE_SIZE);
	}
	for (int i = contentEnd, n = end; i < n; ++i) {
	clearSlot(i % DATA_CACHE_SIZE);
	}
	}
	if (mReloadTask != null) mReloadTask.notifyDirty();
	}

	public void setActiveWindow(int start, int end) {
	if (start == mActiveStart && end == mActiveEnd) return;

	Utils.assertTrue(start <= end
	&& end - start <= mData.length && end <= mSize);

	int length = mData.length;
	mActiveStart = start;
	mActiveEnd = end;

	// If no data is visible, keep the cache content
	if (start == end) return;

	int contentStart = Utils.clamp((start + end) / 2 - length / 2,
	0, Math.max(0, mSize - length));
	int contentEnd = Math.min(contentStart + length, mSize);
	if (mContentStart > start \|\| mContentEnd < end
	\|\| Math.abs(contentStart - mContentStart) > MIN_LOAD_COUNT) {
	setContentWindow(contentStart, contentEnd);
	}
	}

	private class MySourceListener implements ContentListener {
	@Override
	public void onContentDirty() {
	if (mReloadTask != null) mReloadTask.notifyDirty();
	}
	}

	public void setDataListener(DataListener listener) {
	mDataListener.add(listener);
	}

	public void removeDataListener(DataListener listener) {
	mDataListener.remove(listener);
	}

	public void setLoadingListener(LoadingListener listener) {
	mLoadingListener = listener;
	}

	private <T> T executeAndWait(Callable<T> callable) {
	FutureTask<T> task = new FutureTask<T>(callable);
	mMainHandler.sendMessage(
	mMainHandler.obtainMessage(MSG_RUN_OBJECT, task));
	try {
	return task.get();
	} catch (InterruptedException e) {
	return null;
	} catch (ExecutionException e) {
	throw new RuntimeException(e);
	}
	}

	private static class UpdateInfo {
	public long version;
	public int reloadStart;
	public int reloadCount;

	public int size;
	public ArrayList<MediaItem> items;
	}

	private class GetUpdateInfo implements Callable<UpdateInfo> {
	private final long mVersion;

	public GetUpdateInfo(long version) {
	mVersion = version;
	}

	@Override
	public UpdateInfo call() throws Exception {
	if (mFailedVersion == mVersion) {
	// previous loading failed, return null to pause loading
	return null;
	}
	UpdateInfo info = new UpdateInfo();
	long version = mVersion;
	info.version = mSourceVersion;
	info.size = mSize;
	long setVersion[] = mSetVersion;
	for (int i = mContentStart, n = mContentEnd; i < n; ++i) {
	int index = i % DATA_CACHE_SIZE;
	if (setVersion[index] != version) {
	info.reloadStart = i;
	info.reloadCount = Math.min(MAX_LOAD_COUNT, n - i);
	return info;
	}
	}
	return mSourceVersion == mVersion ? null : info;
	}
	}

	private class UpdateContent implements Callable<Void> {

	private UpdateInfo mUpdateInfo;

	public UpdateContent(UpdateInfo info) {
	mUpdateInfo = info;
	}

	@Override
	public Void call() throws Exception {
	UpdateInfo info = mUpdateInfo;
	mSourceVersion = info.version;
	if (mSize != info.size) {
	mSize = info.size;
	if (mDataListener != null)
	for (DataListener l : mDataListener) {
	l.onSizeChanged();
	}
	if (mContentEnd > mSize) mContentEnd = mSize;
	if (mActiveEnd > mSize) mActiveEnd = mSize;
	}

	ArrayList<MediaItem> items = info.items;

	mFailedVersion = MediaObject.INVALID_DATA_VERSION;
	if ((items == null) \|\| items.isEmpty()) {
	if (info.reloadCount > 0) {
	mFailedVersion = info.version;
	Log.d(TAG, "loading failed: " + mFailedVersion);
	}
	return null;
	}
	int start = Math.max(info.reloadStart, mContentStart);
	int end = Math.min(info.reloadStart + items.size(), mContentEnd);

	for (int i = start; i < end; ++i) {
	int index = i % DATA_CACHE_SIZE;
	mSetVersion[index] = info.version;
	MediaItem updateItem = items.get(i - info.reloadStart);
	if (updateItem != null) {
	long itemVersion = updateItem.getDataVersion();
	if (mItemVersion[index] != itemVersion) {
	mItemVersion[index] = itemVersion;
	mData[index] = updateItem;
	if (mDataListener != null && i >= mActiveStart && i < mActiveEnd) {
	for (DataListener l : mDataListener) {
	l.onContentChanged(i);
	}
	}
	}
	}
	}
	return null;
	}
	}

	/*
	* The thread model of ReloadTask
	* *
	* [Reload Task] [Main Thread]
	* \| \|
	* getUpdateInfo() --> \| (synchronous call)
	* (wait) <---- getUpdateInfo()
	* \| \|
	* Load Data \|
	* \| \|
	* updateContent() --> \| (synchronous call)
	* (wait) updateContent()
	* \| \|
	* \| \|
	*/
	private class ReloadTask extends Thread {

	private volatile boolean mActive = true;
	private volatile boolean mDirty = true;
	private boolean mIsLoading = false;

	private void updateLoading(boolean loading) {
	if (mIsLoading == loading) return;
	mIsLoading = loading;
	mMainHandler.sendEmptyMessage(loading ? MSG_LOAD_START : MSG_LOAD_FINISH);
	}

	@Override
	public void run() {
	Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
	boolean updateComplete = false;
	long version = MediaObject.INVALID_DATA_VERSION;
	while (mActive) {
	synchronized (this) {
	if (mActive && !mDirty && updateComplete
	&& version != MediaObject.INVALID_DATA_VERSION) {
	updateLoading(false);
	Utils.waitWithoutInterrupt(this);
	continue;
	}
	mDirty = false;
	}
	updateLoading(true);
	version = mSource.reload();
	UpdateInfo info = executeAndWait(new GetUpdateInfo(version));
	updateComplete = info == null;
	if (updateComplete) {
	continue;
	}
	if (info.version != version) {
	info.size = mSource.getMediaItemCount();
	info.version = version;
	}
	if (info.reloadCount > 0) {
	int start = Math.max(info.reloadStart, mContentStart);
	int end = Math.min(info.reloadStart + info.reloadCount, mContentEnd);
	info.items = mSource.getMediaItem(start, end - start);
	}
	executeAndWait(new UpdateContent(info));
	}
	updateLoading(false);
	}

	public synchronized void notifyDirty() {
	mDirty = true;
	notifyAll();
	}

	public synchronized void terminate() {
	mActive = false;
	notifyAll();
	}
	}
	}