Java tutorial
/* * 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.roach.framework.http.bitmap; 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.support.v4.app.FragmentManager; import android.util.Log; import android.widget.ImageView; import com.roach.framework.BuildConfig; import com.roach.framework.cache.ImageCache; /** * 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 ImageCache mImageCache; private ImageCache.ImageCacheParams mImageCacheParams; private Bitmap mLoadingBitmap; private boolean mFadeInBitmap = true; private boolean mExitTasksEarly = false; protected boolean mPauseWork = false; private final Object mPauseWorkLock = new Object(); 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; 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#setImageCache(ImageCache)}. 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) { loadImage(data, imageView, true, true); } public void loadImage(Object data, ImageView imageView, boolean memoryCache, boolean diskCache) { 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); task.setMemoryCache(memoryCache); task.setDiskCache(diskCache); Drawable drawable = new BitmapDrawable(mResources, mLoadingBitmap); imageView.setTag(task); imageView.setImageDrawable(drawable); // 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(AsyncTask.THREAD_POOL_EXECUTOR, 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 * @param cacheParams */ public void addImageCache(FragmentManager fragmentManager, ImageCache.ImageCacheParams cacheParams) { mImageCacheParams = cacheParams; setImageCache(ImageCache.findOrCreateCache(fragmentManager, mImageCacheParams)); new CacheAsyncTask().execute(MESSAGE_INIT_DISK_CACHE); } public void addImageCache(ImageCache imageCache, ImageCache.ImageCacheParams cacheParams) { mImageCacheParams = cacheParams; setImageCache(imageCache); new CacheAsyncTask().execute(MESSAGE_INIT_DISK_CACHE); } /** * 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; } 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); BitmapWorkerTask bitmapWorkerTask = null; if (imageView.getTag() != null) { bitmapWorkerTask = (BitmapWorkerTask) imageView.getTag(); } 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); BitmapWorkerTask bitmapWorkerTask = null; if (imageView.getTag() != null && (imageView.getTag() instanceof BitmapWorkerTask)) { bitmapWorkerTask = (BitmapWorkerTask) imageView.getTag(); } 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; } public void recycleBitmap(ImageView iv) { BitmapWorkerTask bitmapWorkerTask = null; if (iv.getTag() != null && (iv.getTag() instanceof BitmapWorkerTask)) { bitmapWorkerTask = (BitmapWorkerTask) iv.getTag(); } if (bitmapWorkerTask != null) { Bitmap bitmap = bitmapWorkerTask.getBitmap(); iv.setImageBitmap(null); if (bitmap != null && !bitmap.isRecycled()) { bitmap.recycle(); } iv.setTag(null); bitmapWorkerTask = null; } } /** * The actual AsyncTask that will asynchronously process the image. */ private class BitmapWorkerTask extends AsyncTask<Object, Void, Bitmap> { private Object data; private Bitmap bitmap; private final ImageView imageView; private boolean memoryCache = true; private boolean diskCache = false; public BitmapWorkerTask(ImageView imageView) { this.imageView = imageView; } /** * Background processing. */ @Override protected Bitmap doInBackground(Object... params) { if (BuildConfig.DEBUG) { Log.d(TAG, "doInBackground - starting work:" + this); } Log.d(TAG, "doInBackground - starting work:" + this); data = params[0]; final String dataString = String.valueOf(data); 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() && imageView != 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() && imageView != 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, memoryCache, diskCache); } if (BuildConfig.DEBUG) { Log.d(TAG, "doInBackground - finished work"); } return bitmap; } /** * Once the image is processed, associates it to the imageView */ @Override protected void onPostExecute(Bitmap bp) { // if cancel was called on this task or the "exit early" flag is set then we're done if (isCancelled() || mExitTasksEarly) { bitmap = null; } if (bitmap != null && imageView != null) { if (BuildConfig.DEBUG) { Log.d(TAG, "onPostExecute - setting bitmap"); } setImageBitmap(imageView, bitmap); } } @Override protected void onCancelled(Bitmap bitmap) { super.onCancelled(bitmap); synchronized (mPauseWorkLock) { mPauseWorkLock.notifyAll(); } } public Bitmap getBitmap() { return bitmap; } public void setMemoryCache(boolean memoryCache) { this.memoryCache = memoryCache; } public void setDiskCache(boolean diskCache) { // this.diskCache = diskCache; //TODO: ??????????????http?? this.diskCache = false; } } /** * 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(mResources, bitmap) }); // Set background to loading bitmap if (mLoadingBitmap != null) { imageView.setBackgroundDrawable(new BitmapDrawable(mResources, mLoadingBitmap)); } 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); } }