/*
* Copyright 2012 Google Inc.
*
* 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.google.android.apps.iosched.util;
import com.google.android.apps.iosched.BuildConfig;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.TransitionDrawable;
import android.os.AsyncTask;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.widget.ImageView;
import java.lang.ref.WeakReference;
import java.util.Hashtable;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;
import static com.google.android.apps.iosched.util.LogUtils.LOGD;
import static com.google.android.apps.iosched.util.LogUtils.makeLogTag;
/**
* This class wraps up completing some arbitrary long running work when loading a bitmap to an
* ImageView. It handles things like using a memory and disk cache, running the work in a background
* thread and setting a placeholder image.
*/
public abstract class ImageWorker {
private static final String TAG = makeLogTag(ImageWorker.class);
private static final int FADE_IN_TIME = 200;
protected ImageCache mImageCache;
protected ImageCache.ImageCacheParams mImageCacheParams;
protected Bitmap mLoadingBitmap;
protected boolean mFadeInBitmap = true;
private boolean mExitTasksEarly = false;
protected boolean mPauseWork = false;
private final Object mPauseWorkLock = new Object();
private final Hashtable<Integer, Bitmap> loadingBitmaps = new Hashtable<Integer, Bitmap>(2);
protected Resources mResources;
private static final int MESSAGE_CLEAR = 0;
private static final int MESSAGE_INIT_DISK_CACHE = 1;
private static final int MESSAGE_FLUSH = 2;
private static final int MESSAGE_CLOSE = 3;
private static final ThreadFactory sThreadFactory = new ThreadFactory() {
private final AtomicInteger mCount = new AtomicInteger(1);
public Thread newThread(Runnable r) {
return new Thread(r, "AsyncTask #" + mCount.getAndIncrement());
}
};
// Dual thread executor for main AsyncTask
public static final Executor DUAL_THREAD_EXECUTOR =
Executors.newFixedThreadPool(2, sThreadFactory);
protected ImageWorker(Context context) {
mResources = context.getResources();
}
/**
* Load an image specified by the data parameter into an ImageView (override
* {@link ImageWorker#processBitmap(Object)} to define the processing
* logic). A memory and disk cache will be used if an {@link ImageCache} has
* been set using {@link ImageWorker#addImageCache}. If the
* image is found in the memory cache, it is set immediately, otherwise an
* {@link AsyncTask} will be created to asynchronously load the bitmap.
*
* @param data The URL of the image to download.
* @param imageView The ImageView to bind the downloaded image to.
*/
protected void loadImage(Object data, ImageView imageView) {
loadImage(data, imageView, mLoadingBitmap);
}
/**
* Load an image specified by the data parameter into an ImageView (override
* {@link ImageWorker#processBitmap(Object)} to define the processing
* logic). A memory and disk cache will be used if an {@link ImageCache} has
* been set using {@link ImageWorker#addImageCache}. If the
* image is found in the memory cache, it is set immediately, otherwise an
* {@link AsyncTask} will be created to asynchronously load the bitmap.
*
* @param data The URL of the image to download.
* @param imageView The ImageView to bind the downloaded image to.
* @param resId Resource of placeholder bitmap while the image loads.
*/
protected void loadImage(Object data, ImageView imageView, int resId) {
if (!loadingBitmaps.containsKey(resId)) {
// Store loading bitmap in a hash table to prevent continual decoding
loadingBitmaps.put(resId, BitmapFactory.decodeResource(mResources, resId));
}
loadImage(data, imageView, loadingBitmaps.get(resId));
}
/**
* Load an image specified by the data parameter into an ImageView (override
* {@link ImageWorker#processBitmap(Object)} to define the processing logic). A memory and disk
* cache will be used if an {@link ImageCache} has been set using
* {@link ImageWorker#addImageCache}. If the image is found in the memory cache, it
* is set immediately, otherwise an {@link AsyncTask} will be created to asynchronously load the
* bitmap.
*
* @param data The URL of the image to download.
* @param imageView The ImageView to bind the downloaded image to.
*/
public void loadImage(Object data, ImageView imageView, Bitmap loadingBitmap) {
if (data == null) {
return;
}
Bitmap bitmap = null;
if (mImageCache != null) {
bitmap = mImageCache.getBitmapFromMemCache(String.valueOf(data));
}
if (bitmap != null) {
// Bitmap found in memory cache
imageView.setImageBitmap(bitmap);
} else if (cancelPotentialWork(data, imageView)) {
final BitmapWorkerTask task = new BitmapWorkerTask(imageView);
final AsyncDrawable asyncDrawable =
new AsyncDrawable(mResources, loadingBitmap, task);
imageView.setImageDrawable(asyncDrawable);
if (UIUtils.hasHoneycomb()) {
// On HC+ we execute on a dual thread executor. There really isn't much extra
// benefit to having a really large pool of threads. Having more than one will
// likely benefit network bottlenecks though.
task.executeOnExecutor(DUAL_THREAD_EXECUTOR, data);
} else {
// Otherwise pre-HC the default is a thread pool executor (not ideal, serial
// execution or a smaller number of threads would be better).
task.execute(data);
}
}
}
/**
* Set placeholder bitmap that shows when the the background thread is running.
*
* @param bitmap
*/
public void setLoadingImage(Bitmap bitmap) {
mLoadingBitmap = bitmap;
}
/**
* Set placeholder bitmap that shows when the the background thread is running.
*
* @param resId
*/
public void setLoadingImage(int resId) {
mLoadingBitmap = BitmapFactory.decodeResource(mResources, resId);
}
/**
* Adds an {@link ImageCache} to this worker in the background (to prevent disk access on UI
* thread).
* @param fragmentManager The FragmentManager to initialize and add the cache
* @param cacheParams The cache parameters to use
*/
public void addImageCache(FragmentManager fragmentManager,
ImageCache.ImageCacheParams cacheParams) {
mImageCacheParams = cacheParams;
setImageCache(ImageCache.findOrCreateCache(fragmentManager, mImageCacheParams));
new CacheAsyncTask().execute(MESSAGE_INIT_DISK_CACHE);
}
/**
* Adds an {@link ImageCache} to this worker in the background (to prevent disk access on UI
* thread) using default cache parameters.
* @param fragmentActivity The FragmentActivity to initialize and add the cache
*/
public void addImageCache(FragmentActivity fragmentActivity) {
addImageCache(fragmentActivity.getSupportFragmentManager(),
new ImageCache.ImageCacheParams(fragmentActivity));
}
/**
* Sets the {@link ImageCache} object to use with this ImageWorker. Usually you will not need
* to call this directly, instead use {@link ImageWorker#addImageCache} which will create and
* add the {@link ImageCache} object in a background thread (to ensure no disk access on the
* main/UI thread).
*
* @param imageCache
*/
public void setImageCache(ImageCache imageCache) {
mImageCache = imageCache;
}
/**
* If set to true, the image will fade-in once it has been loaded by the background thread.
*/
public void setImageFadeIn(boolean fadeIn) {
mFadeInBitmap = fadeIn;
}
/**
* Setting this to true will signal the working tasks to exit processing at the next chance.
* This helps finish up pending work when the activity is no longer in the foreground and
* completing the tasks is no longer useful.
* @param exitTasksEarly
*/
public void setExitTasksEarly(boolean exitTasksEarly) {
mExitTasksEarly = exitTasksEarly;
}
/**
* Subclasses should override this to define any processing or work that must happen to produce
* the final bitmap. This will be executed in a background thread and be long running. For
* example, you could resize a large bitmap here, or pull down an image from the network.
*
* @param data The data to identify which image to process, as provided by
* {@link ImageWorker#loadImage(Object, ImageView)}
* @return The processed bitmap
*/
protected abstract Bitmap processBitmap(Object data);
/**
* Cancels any pending work attached to the provided ImageView.
* @param imageView
*/
public static void cancelWork(ImageView imageView) {
final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
if (bitmapWorkerTask != null) {
bitmapWorkerTask.cancel(true);
if (BuildConfig.DEBUG) {
LOGD(TAG, "cancelWork - cancelled work for " + bitmapWorkerTask.data);
}
}
}
/**
* Returns true if the current work has been canceled or if there was no work in
* progress on this image view.
* Returns false if the work in progress deals with the same data. The work is not
* stopped in that case.
*/
public static boolean cancelPotentialWork(Object data, ImageView imageView) {
final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
if (bitmapWorkerTask != null) {
final Object bitmapData = bitmapWorkerTask.data;
if (bitmapData == null || !bitmapData.equals(data)) {
bitmapWorkerTask.cancel(true);
LOGD(TAG, "cancelPotentialWork - cancelled work for " + data);
} else {
// The same work is already in progress.
return false;
}
}
return true;
}
/**
* @param imageView Any imageView
* @return Retrieve the currently active work task (if any) associated with this imageView.
* null if there is no such task.
*/
private static BitmapWorkerTask getBitmapWorkerTask(ImageView imageView) {
if (imageView != null) {
final Drawable drawable = imageView.getDrawable();
if (drawable instanceof AsyncDrawable) {
final AsyncDrawable asyncDrawable = (AsyncDrawable) drawable;
return asyncDrawable.getBitmapWorkerTask();
}
}
return null;
}
/**
* The actual AsyncTask that will asynchronously process the image.
*/
private class BitmapWorkerTask extends AsyncTask<Object, Void, Bitmap> {
private Object data;
private final WeakReference<ImageView> imageViewReference;
public BitmapWorkerTask(ImageView imageView) {
imageViewReference = new WeakReference<ImageView>(imageView);
}
/**
* Background processing.
*/
@Override
protected Bitmap doInBackground(Object... params) {
LOGD(TAG, "doInBackground - starting work");
data = params[0];
final String dataString = String.valueOf(data);
Bitmap bitmap = null;
// Wait here if work is paused and the task is not cancelled
synchronized (mPauseWorkLock) {
while (mPauseWork && !isCancelled()) {
try {
mPauseWorkLock.wait();
} catch (InterruptedException e) {}
}
}
// If the image cache is available and this task has not been cancelled by another
// thread and the ImageView that was originally bound to this task is still bound back
// to this task and our "exit early" flag is not set then try and fetch the bitmap from
// the cache
if (mImageCache != null && !isCancelled() && getAttachedImageView() != null
&& !mExitTasksEarly) {
bitmap = mImageCache.getBitmapFromDiskCache(dataString);
}
// If the bitmap was not found in the cache and this task has not been cancelled by
// another thread and the ImageView that was originally bound to this task is still
// bound back to this task and our "exit early" flag is not set, then call the main
// process method (as implemented by a subclass)
if (bitmap == null && !isCancelled() && getAttachedImageView() != null
&& !mExitTasksEarly) {
bitmap = processBitmap(params[0]);
}
// If the bitmap was processed and the image cache is available, then add the processed
// bitmap to the cache for future use. Note we don't check if the task was cancelled
// here, if it was, and the thread is still running, we may as well add the processed
// bitmap to our cache as it might be used again in the future
if (bitmap != null && mImageCache != null) {
mImageCache.addBitmapToCache(dataString, bitmap);
}
LOGD(TAG, "doInBackground - finished work");
return bitmap;
}
/**
* Once the image is processed, associates it to the imageView
*/
@Override
protected void onPostExecute(Bitmap bitmap) {
// if cancel was called on this task or the "exit early" flag is set then we're done
if (isCancelled() || mExitTasksEarly) {
bitmap = null;
}
final ImageView imageView = getAttachedImageView();
if (bitmap != null && imageView != null) {
LOGD(TAG, "onPostExecute - setting bitmap");
setImageBitmap(imageView, bitmap);
}
}
@Override
protected void onCancelled() {
super.onCancelled();
synchronized (mPauseWorkLock) {
mPauseWorkLock.notifyAll();
}
}
/**
* Returns the ImageView associated with this task as long as the ImageView's task still
* points to this task as well. Returns null otherwise.
*/
private ImageView getAttachedImageView() {
final ImageView imageView = imageViewReference.get();
final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
if (this == bitmapWorkerTask) {
return imageView;
}
return null;
}
}
/**
* A custom Drawable that will be attached to the imageView while the work is in progress.
* Contains a reference to the actual worker task, so that it can be stopped if a new binding is
* required, and makes sure that only the last started worker process can bind its result,
* independently of the finish order.
*/
private static class AsyncDrawable extends BitmapDrawable {
private final WeakReference<BitmapWorkerTask> bitmapWorkerTaskReference;
public AsyncDrawable(Resources res, Bitmap bitmap, BitmapWorkerTask bitmapWorkerTask) {
super(res, bitmap);
bitmapWorkerTaskReference =
new WeakReference<BitmapWorkerTask>(bitmapWorkerTask);
}
public BitmapWorkerTask getBitmapWorkerTask() {
return bitmapWorkerTaskReference.get();
}
}
/**
* Called when the processing is complete and the final bitmap should be set on the ImageView.
*
* @param imageView
* @param bitmap
*/
private void setImageBitmap(ImageView imageView, Bitmap bitmap) {
if (mFadeInBitmap) {
// Use TransitionDrawable to fade in
final TransitionDrawable td =
new TransitionDrawable(new Drawable[] {
new ColorDrawable(android.R.color.transparent),
new BitmapDrawable(mResources, bitmap)
});
//noinspection deprecation
imageView.setBackgroundDrawable(imageView.getDrawable());
imageView.setImageDrawable(td);
td.startTransition(FADE_IN_TIME);
} else {
imageView.setImageBitmap(bitmap);
}
}
public void setPauseWork(boolean pauseWork) {
synchronized (mPauseWorkLock) {
mPauseWork = pauseWork;
if (!mPauseWork) {
mPauseWorkLock.notifyAll();
}
}
}
protected class CacheAsyncTask extends AsyncTask<Object, Void, Void> {
@Override
protected Void doInBackground(Object... params) {
switch ((Integer)params[0]) {
case MESSAGE_CLEAR:
clearCacheInternal();
break;
case MESSAGE_INIT_DISK_CACHE:
initDiskCacheInternal();
break;
case MESSAGE_FLUSH:
flushCacheInternal();
break;
case MESSAGE_CLOSE:
closeCacheInternal();
break;
}
return null;
}
}
protected void initDiskCacheInternal() {
if (mImageCache != null) {
mImageCache.initDiskCache();
}
}
protected void clearCacheInternal() {
if (mImageCache != null) {
mImageCache.clearCache();
}
}
protected void flushCacheInternal() {
if (mImageCache != null) {
mImageCache.flush();
}
}
protected void closeCacheInternal() {
if (mImageCache != null) {
mImageCache.close();
mImageCache = null;
}
}
public void clearCache() {
new CacheAsyncTask().execute(MESSAGE_CLEAR);
}
public void flushCache() {
new CacheAsyncTask().execute(MESSAGE_FLUSH);
}
public void closeCache() {
new CacheAsyncTask().execute(MESSAGE_CLOSE);
}
}