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/*
* 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.ui;
import android.graphics.Bitmap;
import com.android.gallery3d.util.Future;
import com.android.gallery3d.util.FutureListener;
// We use this class to
// 1.) load bitmaps in background.
// 2.) as a place holder for the loaded bitmap
public abstract class BitmapLoader implements FutureListener<Bitmap> {
@SuppressWarnings("unused")
private static final String TAG = "BitmapLoader";
/* Transition Map:
* INIT -> REQUESTED, RECYCLED
* REQUESTED -> INIT (cancel), LOADED, ERROR, RECYCLED
* LOADED, ERROR -> RECYCLED
*/
private static final int STATE_INIT = 0;
private static final int STATE_REQUESTED = 1;
private static final int STATE_LOADED = 2;
private static final int STATE_ERROR = 3;
private static final int STATE_RECYCLED = 4;
private int mState = STATE_INIT;
// mTask is not null only when a task is on the way
private Future<Bitmap> mTask;
private Bitmap mBitmap;
@Override
public void onFutureDone(Future<Bitmap> future) {
synchronized (this) {
mTask = null;
mBitmap = future.get();
if (mState == STATE_RECYCLED) {
if (mBitmap != null) {
recycleBitmap(mBitmap);
mBitmap = null;
}
return; // don't call callback
}
if (future.isCancelled() && mBitmap == null) {
if (mState == STATE_REQUESTED) mTask = submitBitmapTask(this);
return; // don't call callback
} else {
mState = mBitmap == null ? STATE_ERROR : STATE_LOADED;
}
}
onLoadComplete(mBitmap);
}
public synchronized void startLoad() {
if (mState == STATE_INIT) {
mState = STATE_REQUESTED;
if (mTask == null) mTask = submitBitmapTask(this);
}
}
public synchronized void cancelLoad() {
if (mState == STATE_REQUESTED) {
mState = STATE_INIT;
if (mTask != null) mTask.cancel();
}
}
// Recycle the loader and the bitmap
public synchronized void recycle() {
mState = STATE_RECYCLED;
if (mBitmap != null) {
recycleBitmap(mBitmap);
mBitmap = null;
}
if (mTask != null) mTask.cancel();
}
public synchronized boolean isRequestInProgress() {
return mState == STATE_REQUESTED;
}
public synchronized boolean isRecycled() {
return mState == STATE_RECYCLED;
}
public synchronized Bitmap getBitmap() {
return mBitmap;
}
abstract protected Future<Bitmap> submitBitmapTask(FutureListener<Bitmap> l);
abstract protected void recycleBitmap(Bitmap bitmap);
abstract protected void onLoadComplete(Bitmap bitmap);
}
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