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.baseproject.image; import java.lang.ref.WeakReference; import android.annotation.SuppressLint; 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.os.Build; import android.support.v4.app.FragmentActivity; import android.text.TextUtils; import android.widget.ImageView; import com.youku.analytics.data.Device; //import com.youku.util.Logger; /** * 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 Bitmap mLoadingBitmap; private boolean mFadeInBitmap = true; private boolean mExitTasksEarly = false; protected Context mContext; protected ImageWorkerAdapter mImageWorkerAdapter; /** * ?? */ private static ImageWorker imageWorker; public static final ImageWorker getInstance(FragmentActivity context) { if (null == imageWorker) { final int height = Device.ht; final int width = Device.wt; final int shortest = height > width ? width : height; imageWorker = new ImageFetcher(context, shortest); imageWorker.setImageCache(ImageCache.findOrCreateCache(context, Utils.IMAGE_CACHE_DIR)); imageWorker.setImageFadeIn(true); } return imageWorker; } 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 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 bitmap = null; if (mImageCache != null) { bitmap = mImageCache.getBitmapFromMemCache(String.valueOf(data)); } if (bitmap != null) { // Bitmap found in memory cache if (null != imageView) { imageView.setImageBitmap(bitmap); } } else if (cancelPotentialWork(data, imageView)) { final BitmapWorkerTask task = new BitmapWorkerTask(imageView); final AsyncDrawable asyncDrawable = new AsyncDrawable(mContext.getResources(), mLoadingBitmap, task); if (null != imageView) { imageView.setImageDrawable(asyncDrawable); } task.execute(data); } } public void loadImage(Object data, ImageView imageView, ImageCallback imageCallback) { Bitmap bitmap = null; if (mImageCache != null) { bitmap = mImageCache.getBitmapFromMemCache(String.valueOf(data)); } if (bitmap != null) { // Bitmap found in memory cache if (null != imageView) { imageView.setImageBitmap(bitmap); } if (imageCallback != null) { imageCallback.imageLoaded(bitmap, String.valueOf(data)); } } else if (cancelPotentialWork(data, imageView)) { final BitmapWorkerTask task = new BitmapWorkerTask(imageView, imageCallback); final AsyncDrawable asyncDrawable = new AsyncDrawable(mContext.getResources(), mLoadingBitmap, task); if (null != imageView) { imageView.setImageDrawable(asyncDrawable); } task.execute(data); } } /** * 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 AsyncTask} 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 void loadImage(int num, ImageView imageView) { if (mImageWorkerAdapter != null) { loadImage(mImageWorkerAdapter.getItem(num), imageView); } 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, ImageView mImageView); public static void cancelWork(ImageView imageView) { final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView); if (bitmapWorkerTask != null) { bitmapWorkerTask.cancel(true); final Object bitmapData = bitmapWorkerTask.data; // Logger.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); // Logger.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 AsyncTask that will asynchronously process the image. */ private class BitmapWorkerTask extends ImageAsyncTask<Object, Void, Bitmap> { private Object data; private final WeakReference<ImageView> imageViewReference; private ImageCallback imageCallback; public BitmapWorkerTask(ImageView imageView) { imageViewReference = new WeakReference<ImageView>(imageView); } public BitmapWorkerTask(ImageView imageView, ImageCallback imageCallback) { imageViewReference = new WeakReference<ImageView>(imageView); this.imageCallback = imageCallback; } /** * 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) { ImageView mImageView = getAttachedImageView(); bitmap = processBitmap(params[0], mImageView); } // 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 (null != mImageCache) { if (null != bitmap) { mImageCache.addBitmapToCache(dataString, bitmap); } else if (null != mImageCache.getDiskCache()) { if (!TextUtils.isEmpty(dataString)) { mImageCache.getDiskCache().removeFile(Utils.urlToFileName(dataString)); } } } 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); } if (null != imageCallback) { imageCallback.imageLoaded(bitmap, String.valueOf(data)); } } /** * 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 */ @SuppressWarnings("deprecation") @SuppressLint("NewApi") private void setImageBitmap(ImageView imageView, Bitmap bitmap) { if (mFadeInBitmap) { if (imageView.getTag() instanceof String && "no_animation".equals(String.valueOf(imageView.getTag()))) { imageView.setImageBitmap(bitmap); } else { // Transition drawable with a transparent drwabale and the final // bitmap TransitionDrawable td = new TransitionDrawable( new Drawable[] { new ColorDrawable(android.R.color.transparent), new BitmapDrawable(mContext.getResources(), bitmap) }); final WeakReference<TransitionDrawable> tdReference = new WeakReference<TransitionDrawable>(td); td = null; // Set background to loading bitmap final BitmapDrawable bd = new BitmapDrawable(mContext.getResources(), mLoadingBitmap); if (Build.VERSION.SDK_INT >= 16) { imageView.setBackground(bd); } else { imageView.setBackgroundDrawable(bd); } if (null != tdReference.get()) { imageView.setImageDrawable(tdReference.get()); tdReference.get().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(); } }