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.ruoogle.base.imgload; 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 java.lang.ref.WeakReference; import java.util.ArrayList; import java.util.List; import com.ruoogle.base.BaseBlockImageShow; import com.ruoogle.base.BuildConfig; /** * 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; private Context mContext; protected ImageWorker(Context context) { mResources = context.getResources(); 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 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(List<String> aURLList, ImageView imageView) { /*??*/ if ((aURLList == null) || (aURLList.size() == 0)) { return; } List<String> sURLList = aURLList;//Imageview? List<Bitmap> sBitmaplist = new ArrayList<Bitmap>();//URLBitmap List<String> sNoMemCacheURL = new ArrayList<String>();//Memory Cache?URL /*load bitmap from memory cache*/ if (mImageCache != null) { Bitmap bitmap = null; for (int i = 0; i < sURLList.size(); i++) { bitmap = mImageCache.getBitmapFromMemCache(sURLList.get(i)); if (bitmap != null) { sBitmaplist.add(bitmap); } else { sNoMemCacheURL.add(sURLList.get(i)); } } } /**/ if (sNoMemCacheURL.size() == 0) { BaseBlockImageShow tmpBaseBlockImageShow = new BaseBlockImageShow(mContext); imageView.setImageDrawable(tmpBaseBlockImageShow.getImageViewBitmapLayer(sBitmaplist)); Log.d(TAG, "Memory cache to show bitmaps..."); } else if (cancelPotentialWork(sURLList, imageView)) { final BitmapWorkerTask task = new BitmapWorkerTask(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(AsyncTask.DUAL_THREAD_EXECUTOR, sNoMemCacheURL, sBitmaplist); } } public void loadImage(String aURL, ImageView imageView) { if (aURL == null) { return; } List<String> sURLList = new ArrayList<String>();//Imageview? sURLList.add(aURL); List<Bitmap> sBitmaplist = new ArrayList<Bitmap>();//URLBitmap Bitmap bitmap = null; if (mImageCache != null) { bitmap = mImageCache.getBitmapFromMemCache(aURL); } if (bitmap != null) { // Bitmap found in memory cache imageView.setImageBitmap(bitmap); } else if (cancelPotentialWork(sURLList, imageView)) { final BitmapWorkerTask task = new BitmapWorkerTask(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(AsyncTask.DUAL_THREAD_EXECUTOR, sURLList, sBitmaplist); } } /** * 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); } /** * 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); /** * Subclasses should override this to defind any process or work that must happen to produce * the final bitmap.you should resize a large bitmap * @param data * @return */ protected abstract Bitmap processLocalBitmap(String filePath); /** * 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.sURLList; 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(List<String> sURLList, ImageView imageView) { final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView); if (bitmapWorkerTask != null) { final Object bitmapData = bitmapWorkerTask.sURLList; if (bitmapData == null || !sURLList.equals(bitmapData)) { bitmapWorkerTask.cancel(true); if (BuildConfig.DEBUG) { Log.d(TAG, "cancelPotentialWork - cancelled work for " + sURLList); } } 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, List<Bitmap>> { private List<String> sURLList; private final WeakReference<ImageView> imageViewReference; public BitmapWorkerTask(ImageView imageView) { imageViewReference = new WeakReference<ImageView>(imageView); } /** * Background processing. */ @Override protected List<Bitmap> doInBackground(Object... params) { /*ImageViewURLURL*/ sURLList = (List<String>) params[0]; if (BuildConfig.DEBUG) { Log.d(TAG, "doInBackground - starting work" + sURLList + "****"); } /*ImageView??BitmapBitmap?Memory Cache?*/ List<Bitmap> sBitmapList = (List<Bitmap>) params[1]; /*??*/ for (int i = 0; i < sURLList.size(); i++) { final String sOneURL = sURLList.get(i); 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(sOneURL); } // 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).first process the local file if (bitmap == null && !isCancelled() && getAttachedImageView() != null && !mExitTasksEarly) { bitmap = processLocalBitmap(sOneURL); } // 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(sOneURL); } // 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(sOneURL, bitmap); } if (BuildConfig.DEBUG) { Log.d(TAG, "doInBackground - finished work"); } sBitmapList.add(bitmap); } return sBitmapList; } /** * Once the image is processed, associates it to the imageView */ @Override protected void onPostExecute(List<Bitmap> aBitmapList) { // if cancel was called on this task or the "exit early" flag is set then we're done if (isCancelled() || mExitTasksEarly) { aBitmapList = null; } final ImageView imageView = getAttachedImageView(); if (aBitmapList != null && imageView != null) { if (BuildConfig.DEBUG) { Log.d(TAG, "onPostExecute - setting bitmap"); } if (aBitmapList.size() == 1) { setImageBitmap(imageView, aBitmapList.get(0) == null ? null : new BitmapDrawable(aBitmapList.get(0))); } else { BaseBlockImageShow tmpBaseBlockImageShow = new BaseBlockImageShow(mContext); setImageBitmap(imageView, tmpBaseBlockImageShow.getImageViewBitmapLayer(aBitmapList)); } } } @Override protected void onCancelled(List<Bitmap> aBitmapList) { super.onCancelled(aBitmapList); 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, Drawable aDrawable) { 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), aDrawable }); // Set background to loading bitmap imageView.setBackgroundDrawable(new BitmapDrawable(mResources, mLoadingBitmap)); imageView.setImageDrawable(td); td.startTransition(FADE_IN_TIME); } else { /*aDrawable??*/ if (aDrawable == null) { imageView.setImageBitmap(mLoadingBitmap); } else { imageView.setImageDrawable(aDrawable); } } } 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); } }