com.androidpi.bricks.gallery.lru.cache.ImageWorker.java Source code

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/*
 * 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.androidpi.bricks.gallery.lru.cache;

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.util.Log;
import android.widget.ImageView;
import android.widget.Toast;

import com.androidpi.app.bricks.common.AppUtil;
import com.androidpi.bricks.gallery.BuildConfig;
import com.androidpi.bricks.gallery.task.AsyncExecutor;

import java.lang.ref.WeakReference;

/**
 * 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 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 final Object mPauseWorkLock = new Object();
    protected boolean mPauseWork = false;
    protected Resources mResources;
    private Context mContext;
    private ImageCache mImageCache;
    private ImageCache.ImageCacheParams mImageCacheParams;
    private Bitmap mLoadingBitmap;
    private boolean mFadeInBitmap = true;
    private boolean mExitTasksEarly = false;

    protected ImageWorker(Context context) {
        mContext = context;
        mResources = context.getResources();
    }

    /**
     * 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) {
                final Object bitmapData = bitmapWorkerTask.mData;
                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) {
        // BEGIN_INCLUDE(cancel_potential_work)
        final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);

        if (bitmapWorkerTask != null) {
            final Object bitmapData = bitmapWorkerTask.mData;
            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;
        // END_INCLUDE(cancel_potential_work)
    }

    /**
     * @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;
    }

    /**
     * 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 added using {@link
     * ImageWorker#addImageCache(android.support.v4.app.FragmentManager,
     * ImageCache.ImageCacheParams)} . 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) {
        if (data == null) {
            return;
        }

        BitmapDrawable value = null;

        if (mImageCache != null) {
            value = mImageCache.getBitmapFromMemCache(String.valueOf(data));
        }

        if (value != null) {
            // Bitmap found in memory cache
            imageView.setImageDrawable(value);
        } else if (cancelPotentialWork(data, imageView)) {
            // BEGIN_INCLUDE(execute_background_task)
            final BitmapWorkerTask task = new BitmapWorkerTask(data, imageView);
            final AsyncDrawable asyncDrawable = new AsyncDrawable(mResources, mLoadingBitmap, task);
            imageView.setImageDrawable(asyncDrawable);

            // NOTE: This uses a custom version of AsyncTask that has been
            // pulled from the
            // framework and slightly modified. Refer to the docs at the top of
            // the class
            // for more info on what was changed.
            task.executeOnExecutor(AsyncExecutor.instance().THREAD_POOL_EXECUTOR);
            // END_INCLUDE(execute_background_task)
        }
    }

    /**
     * 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 {@link ImageWorker} to handle disk and memory bitmap
     * caching.
     *
     * @param fragmentManager
     * @param cacheParams The cache parameters to use for the image cache.
     */
    public void addImageCache(FragmentManager fragmentManager, ImageCache.ImageCacheParams cacheParams) {
        mImageCacheParams = cacheParams;
        mImageCache = ImageCache.getInstance(fragmentManager, mImageCacheParams);
        new CacheAsyncTask().execute(MESSAGE_INIT_DISK_CACHE);
    }

    /**
     * Adds an {@link ImageCache} to this {@link ImageWorker} to handle disk and memory bitmap
     * caching.
     *
     * @param activity
     * @param diskCacheDirectoryName See {@link
     *     ImageCache.ImageCacheParams#ImageCacheParams(android.content.Context, String)} .
     */
    public void addImageCache(FragmentActivity activity, String diskCacheDirectoryName) {
        mImageCacheParams = new ImageCache.ImageCacheParams(activity, diskCacheDirectoryName);
        mImageCache = ImageCache.getInstance(activity.getSupportFragmentManager(), mImageCacheParams);
        new CacheAsyncTask().execute(MESSAGE_INIT_DISK_CACHE);
    }

    /** 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;
    }

    public void setExitTasksEarly(boolean exitTasksEarly) {
        mExitTasksEarly = exitTasksEarly;
        setPauseWork(false);
    }

    /**
     * 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, android.widget.ImageView)}
     * @return The processed bitmap
     */
    protected abstract Bitmap processBitmap(Object data);

    /** @return The {@link ImageCache} object currently being used by this ImageWorker. */
    protected ImageCache getImageCache() {
        return mImageCache;
    }

    /**
     * Called when the processing is complete and the final drawable should be set on the ImageView.
     *
     * @param imageView
     * @param drawable
     */
    private void setImageDrawable(ImageView imageView, Drawable drawable) {
        if (mFadeInBitmap) {
            // Transition drawable with a transparent drawable and the final
            // drawable
            final TransitionDrawable td = new TransitionDrawable(new Drawable[] {
                    new ColorDrawable(imageView.getResources().getColor(android.R.color.transparent)), drawable });
            // Set background to loading bitmap
            imageView.setBackgroundDrawable(new BitmapDrawable(mResources, mLoadingBitmap));

            imageView.setImageDrawable(td);
            td.startTransition(FADE_IN_TIME);
        } else {
            imageView.setImageDrawable(drawable);
        }
    }

    /**
     * Pause any ongoing background work. This can be used as a temporary measure to improve
     * performance. For example background work could be paused when a ListView or GridView is being
     * scrolled using a {@link android.widget.AbsListView.OnScrollListener} to keep scrolling
     * smooth.
     *
     * <p>If work is paused, be sure setPauseWork(false) is called again before your fragment or
     * activity is destroyed (for example during {@link android.app.Activity#onPause()}), or there
     * is a risk the background thread will never finish.
     */
    public void setPauseWork(boolean pauseWork) {
        synchronized (mPauseWorkLock) {
            mPauseWork = pauseWork;
            if (!mPauseWork) {
                mPauseWorkLock.notifyAll();
            }
        }
    }

    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);
    }

    /**
     * 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();
        }
    }

    /** The actual AsyncTask that will asynchronously process the image. */
    private class BitmapWorkerTask extends AsyncTask<Void, Void, BitmapDrawable> {
        private final WeakReference<ImageView> imageViewReference;
        private Object mData;

        public BitmapWorkerTask(Object data, ImageView imageView) {
            mData = data;
            imageViewReference = new WeakReference<ImageView>(imageView);
        }

        /** Background processing. */
        @Override
        protected BitmapDrawable doInBackground(Void... params) {
            // BEGIN_INCLUDE(load_bitmap_in_background)
            if (BuildConfig.DEBUG) {
                Log.d(TAG, "doInBackground - starting work");
            }

            final String dataString = String.valueOf(mData);
            Bitmap bitmap = null;
            BitmapDrawable drawable = 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(mData);
            }

            // 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) {
                if (AppUtil.hasHoneycomb()) {
                    // Running on Honeycomb or newer, so wrap in a standard
                    // BitmapDrawable
                    drawable = new BitmapDrawable(mResources, bitmap);
                } else {
                    // Running on Gingerbread or older, so wrap in a
                    // RecyclingBitmapDrawable
                    // which will recycle automagically
                    drawable = new RecyclingBitmapDrawable(mResources, bitmap);
                }

                if (mImageCache != null) {
                    mImageCache.addBitmapToCache(dataString, drawable);
                }
            }

            if (BuildConfig.DEBUG) {
                Log.d(TAG, "doInBackground - finished work");
            }

            return drawable;
            // END_INCLUDE(load_bitmap_in_background)
        }

        /** Once the image is processed, associates it to the imageView */
        @Override
        protected void onPostExecute(BitmapDrawable value) {
            // BEGIN_INCLUDE(complete_background_work)
            // if cancel was called on this task or the "exit early" flag is set
            // then we're done
            if (isCancelled() || mExitTasksEarly) {
                value = null;
            }

            final ImageView imageView = getAttachedImageView();
            if (value != null && imageView != null) {
                if (BuildConfig.DEBUG) {
                    Log.d(TAG, "onPostExecute - setting bitmap");
                }
                setImageDrawable(imageView, value);
            }
            // END_INCLUDE(complete_background_work)
        }

        @Override
        protected void onCancelled(BitmapDrawable value) {
            super.onCancelled(value);
            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;
        }
    }

    protected class CacheAsyncTask extends AsyncTask<Object, Void, Object> {

        @Override
        protected Object doInBackground(Object... params) {
            int message = (Integer) params[0];
            switch (message) {
            case MESSAGE_CLEAR:
                clearCacheInternal();
                break;
            case MESSAGE_INIT_DISK_CACHE:
                initDiskCacheInternal();
                break;
            case MESSAGE_FLUSH:
                flushCacheInternal();
                break;
            case MESSAGE_CLOSE:
                closeCacheInternal();
                break;
            }
            return message;
        }

        @Override
        protected void onPostExecute(Object result) {
            int message = (Integer) result;
            switch (message) {
            case MESSAGE_CLEAR:
                Toast.makeText(mContext, "Cache cleared.", Toast.LENGTH_SHORT).show();
                break;
            }
        }
    }
}