/*
* Copyright (C) 2012 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.ustc.dystu.dandelion.utils.image;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
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.util.Log;
import android.widget.ImageView;
import com.ustc.dystu.dandelion.BuildConfig;
import com.ustc.dystu.dandelion.utils.DandAsyncTask;
/**
* 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 = "ImageWorker";
private static final int FADE_IN_TIME = 200;
private static final int MAX_TASK_NUM = 20;
private ImageCache mImageCache;
private Bitmap mLoadingBitmap;
private boolean mFadeInBitmap = true;
private boolean mExitTasksEarly = false;
protected Context mContext;
protected ImageWorkerAdapter mImageWorkerAdapter;
private ArrayList<WeakReference<BitmapWorkerTask>> mTaskList = new ArrayList<WeakReference<BitmapWorkerTask>>();
protected ImageWorker(Context context) {
mContext = context;
}
/**
* 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#setImageCache(ImageCache)}. If the
* image is found in the memory cache, it is set immediately, otherwise an
* {@link DandAsyncTask} 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 boolean loadImage(Object data, ImageView imageView,
boolean needDownload) {
return loadImage(data, imageView, mLoadingBitmap, needDownload);
}
public boolean loadImage(Object data, ImageView imageView,
Bitmap loadingBitmap, boolean needDownload) {
Bitmap bitmap = null;
if (mImageCache != null) {
bitmap = mImageCache.getBitmapFromMemCache(String.valueOf(data));
if (bitmap != null && bitmap.isRecycled()) {
bitmap = null;
}
}
if (bitmap != null) {
imageView.setImageBitmap(bitmap);
return true;
} else {
if (needDownload && cancelPotentialWork(data, imageView)) {
final BitmapWorkerTask task = new BitmapWorkerTask(imageView);
final AsyncDrawable asyncDrawable = new AsyncDrawable(
mContext.getResources(), loadingBitmap, task);
imageView.setImageDrawable(asyncDrawable);
executeTask(task, data);
}
return false;
}
}
private void executeTask(BitmapWorkerTask task, Object data) {
if (mTaskList.size() >= MAX_TASK_NUM) {
BitmapWorkerTask bitmapWorkerTask = mTaskList.get(0).get();
if (bitmapWorkerTask != null) {
bitmapWorkerTask.cancel(true);
}
mTaskList.remove(0);
}
mTaskList.add(new WeakReference<ImageWorker.BitmapWorkerTask>(task));
try {
task.execute(data);
} catch (Exception e) {
e.printStackTrace();
}
}
public boolean loadImage(Object data, ImageView imageView, int loadingRes,
boolean needDownload) {
Bitmap loadingBitmap = BitmapFactory.decodeResource(
mContext.getResources(), loadingRes);
return loadImage(data, imageView, loadingBitmap, needDownload);
}
/**
* Load an image specified from a set adapter 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#setImageCache(ImageCache)}. If the
* image is found in the memory cache, it is set immediately, otherwise an
* {@link DandAsyncTask} will be created to asynchronously load the bitmap.
* {@link ImageWorker#setAdapter(ImageWorkerAdapter)} must be called before
* using this method.
*
* @param data
* The URL of the image to download.
* @param imageView
* The ImageView to bind the downloaded image to.
*/
public boolean loadImage(int num, ImageView imageView) {
if (mImageWorkerAdapter != null) {
return loadImage(mImageWorkerAdapter.getItem(num), imageView, true);
} else {
throw new NullPointerException(
"Data not set, must call setAdapter() first.");
}
}
/**
* 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(mContext.getResources(),
resId);
}
/**
* Set the {@link ImageCache} object to use with this ImageWorker.
*
* @param cacheCallback
*/
public void setImageCache(ImageCache cacheCallback) {
mImageCache = cacheCallback;
}
public ImageCache getImageCache() {
return mImageCache;
}
/**
* If set to true, the image will fade-in once it has been loaded by the
* background thread.
*
* @param fadeIn
*/
public void setImageFadeIn(boolean fadeIn) {
mFadeInBitmap = fadeIn;
}
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);
public static void cancelWork(ImageView imageView) {
final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
if (bitmapWorkerTask != null) {
bitmapWorkerTask.cancel(true);
if (BuildConfig.DEBUG) {
final Object bitmapData = bitmapWorkerTask.data;
Log.d(TAG, "cancelWork - cancelled work for " + bitmapData);
}
}
}
/**
* 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);
if (BuildConfig.DEBUG) {
Log.d(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 VdiskAsyncTask that will asynchronously process the image.
*/
private class BitmapWorkerTask extends DandAsyncTask<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) {
data = params[0];
final String dataString = String.valueOf(data);
Bitmap bitmap = null;
// 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, true);
}
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) {
setImageBitmap(imageView, bitmap);
}
}
/**
* 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) {
// Transition drawable with a transparent drwabale and the final
// bitmap
final TransitionDrawable td = new TransitionDrawable(
new Drawable[] {
new ColorDrawable(android.R.color.transparent),
new BitmapDrawable(mContext.getResources(), bitmap) });
// Set background to loading bitmap
imageView.setBackgroundDrawable(new BitmapDrawable(mContext
.getResources(), mLoadingBitmap));
imageView.setImageDrawable(td);
td.startTransition(FADE_IN_TIME);
} else {
imageView.setImageBitmap(bitmap);
}
}
/**
* Set the simple adapter which holds the backing data.
*
* @param adapter
*/
public void setAdapter(ImageWorkerAdapter adapter) {
mImageWorkerAdapter = adapter;
}
/**
* Get the current adapter.
*
* @return
*/
public ImageWorkerAdapter getAdapter() {
return mImageWorkerAdapter;
}
/**
* A very simple adapter for use with ImageWorker class and subclasses.
*/
public static abstract class ImageWorkerAdapter {
public abstract Object getItem(int num);
public abstract int getSize();
}
}