Java tutorial
package se.dw.okhttpwrapper; /* * Copyright (C) 2010 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. */ import java.io.BufferedInputStream; import java.io.FilterInputStream; import java.io.IOException; import java.io.InputStream; import java.lang.ref.SoftReference; import java.lang.ref.WeakReference; import java.net.HttpURLConnection; import java.net.URL; import java.util.HashMap; import java.util.LinkedHashMap; import java.util.concurrent.ConcurrentHashMap; import org.apache.http.util.ByteArrayBuffer; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Bitmap.CompressFormat; import android.graphics.BitmapFactory; import android.graphics.Color; import android.graphics.drawable.ColorDrawable; import android.graphics.drawable.Drawable; import android.os.AsyncTask; import android.os.Handler; import android.util.Log; import android.widget.ImageView; import com.squareup.okhttp.OkHttpClient; /** * https://code.google.com/p/android-imagedownloader/ * * This helper class download images from the Internet and binds those with the provided ImageView. * * <p>It requires the INTERNET permission, which should be added to your application's manifest * file.</p> * * A local cache of downloaded images is maintained internally to improve performance. */ public class ImageRequest { private static ImageRequest imageDownloader = null; private static int maxImageWidth = 300; private static int maxImageHeight = 300; private static DiskLruImageCache fileCache = null; public static ImageRequest initiateWDiskCache(Context context, int inMaxImageWidth, int inMaxImageHeight, int cacheSize) { maxImageWidth = inMaxImageWidth; maxImageHeight = inMaxImageHeight; cacheSize = cacheSize * 1024 * 1024; String uniqueName = context.getApplicationInfo().packageName; fileCache = new DiskLruImageCache(context, uniqueName, cacheSize, CompressFormat.PNG, 100); imageDownloader = null; return getInstance(); } public static ImageRequest getInstance() { if (imageDownloader == null) { imageDownloader = new ImageRequest(); imageDownloader.setMode(ImageRequest.Mode.CORRECT); } return imageDownloader; } private static final String LOG_TAG = "ImageRequest"; public enum Mode { NO_ASYNC_TASK, CORRECT } private Mode mode = Mode.CORRECT; /** * Download the specified image from the Internet and binds it to the provided ImageView. The * binding is immediate if the image is found in the cache and will be done asynchronously * otherwise. A null bitmap will be associated to the ImageView if an error occurs. * * @param url The URL of the image to download. * @param imageView The ImageView to bind the downloaded image to. */ public void execute(String url, ImageView imageView) { resetPurgeTimer(); Bitmap bitmap = getBitmapFromCache(url); if (bitmap == null) { forceDownload(url, imageView); } else { cancelPotentialDownload(url, imageView); imageView.setImageBitmap(bitmap); } } /* * Same as download but the image is always downloaded and the cache is not used. * Kept private at the moment as its interest is not clear. private void forceDownload(String url, ImageView view) { forceDownload(url, view, null); } */ /** * Same as download but the image is always downloaded and the cache is not used. * Kept private at the moment as its interest is not clear. */ private void forceDownload(String url, ImageView imageView) { // State sanity: url is guaranteed to never be null in DownloadedDrawable and cache keys. if (url == null) { imageView.setImageDrawable(null); return; } if (cancelPotentialDownload(url, imageView)) { switch (mode) { case NO_ASYNC_TASK: Bitmap bitmap = downloadBitmap(url); addBitmapToCache(url, bitmap); imageView.setImageBitmap(bitmap); break; case CORRECT: BitmapDownloaderTask task = new BitmapDownloaderTask(imageView); DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task); imageView.setImageDrawable(downloadedDrawable); imageView.setMinimumHeight(156); task.execute(url); break; } } } /** * Returns true if the current download has been canceled or if there was no download in * progress on this image view. * Returns false if the download in progress deals with the same url. The download is not * stopped in that case. */ private static boolean cancelPotentialDownload(String url, ImageView imageView) { BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView); if (bitmapDownloaderTask != null) { String bitmapUrl = bitmapDownloaderTask.url; if ((bitmapUrl == null) || (!bitmapUrl.equals(url))) { bitmapDownloaderTask.cancel(true); } else { // The same URL is already being downloaded. return false; } } return true; } /** * @param imageView Any imageView * @return Retrieve the currently active download task (if any) associated with this imageView. * null if there is no such task. */ private static BitmapDownloaderTask getBitmapDownloaderTask(ImageView imageView) { if (imageView != null) { Drawable drawable = imageView.getDrawable(); if (drawable instanceof DownloadedDrawable) { DownloadedDrawable downloadedDrawable = (DownloadedDrawable) drawable; return downloadedDrawable.getBitmapDownloaderTask(); } } return null; } private Bitmap downloadBitmap(String url) { OkHttpClient client = OkHttpWrapper.getClient(); if (client == null) { Log.w(LOG_TAG, "OkHttpWrapper not initialized, " + url); return null; } InputStream in = null; HttpURLConnection connection = null; try { connection = client.open(new URL(url)); /* * http://stackoverflow.com/questions/10550349/retriving-image-from-server-to-android-app * Reading directly from stream sometimes BitmapFactory returns null. */ in = connection.getInputStream(); BufferedInputStream bis = new BufferedInputStream(in, 8190); ByteArrayBuffer baf = new ByteArrayBuffer(50); int current = 0; while ((current = bis.read()) != -1) { baf.append((byte) current); } byte[] imageData = baf.toByteArray(); BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeByteArray(imageData, 0, imageData.length, options); int reqWidth = maxImageWidth; int reqHeight = maxImageHeight; options.inJustDecodeBounds = false; options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight); Bitmap bitmap = BitmapFactory.decodeByteArray(imageData, 0, imageData.length, options); return bitmap; } catch (IOException e) { Log.w(LOG_TAG, "I/O error while retrieving bitmap from " + url + "\n" + e.toString()); } catch (IllegalStateException e) { Log.w(LOG_TAG, "Incorrect URL: " + url); } catch (Exception e) { Log.w(LOG_TAG, "Error while retrieving bitmap from " + url, e); } finally { if (in != null) { } if (connection != null) { } } return null; } public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) { // Raw height and width of image final int height = options.outHeight; final int width = options.outWidth; int inSampleSize = 1; if (height > reqHeight || width > reqWidth) { final int halfHeight = height / 2; final int halfWidth = width / 2; // Calculate the largest inSampleSize value that is a power of 2 and keeps both // height and width larger than the requested height and width. while ((halfHeight / inSampleSize) > reqHeight && (halfWidth / inSampleSize) > reqWidth) { inSampleSize *= 2; } } return inSampleSize; } /* * An InputStream that skips the exact number of bytes provided, unless it reaches EOF. */ static class FlushedInputStream extends FilterInputStream { public FlushedInputStream(InputStream inputStream) { super(inputStream); } @Override public long skip(long n) throws IOException { long totalBytesSkipped = 0L; while (totalBytesSkipped < n) { long bytesSkipped = in.skip(n - totalBytesSkipped); if (bytesSkipped == 0L) { int b = read(); if (b < 0) { break; // we reached EOF } else { bytesSkipped = 1; // we read one byte } } totalBytesSkipped += bytesSkipped; } return totalBytesSkipped; } } /** * The actual AsyncTask that will asynchronously download the image. */ class BitmapDownloaderTask extends AsyncTask<String, Void, Bitmap> { private String url; private final WeakReference<ImageView> imageViewReference; public BitmapDownloaderTask(ImageView imageView) { imageViewReference = new WeakReference<ImageView>(imageView); } /** * Actual download method. */ @Override protected Bitmap doInBackground(String... params) { url = params[0]; return downloadBitmap(url); } /** * Once the image is downloaded, associates it to the imageView */ @Override protected void onPostExecute(Bitmap bitmap) { if (isCancelled()) { bitmap = null; } addBitmapToCache(url, bitmap); if (imageViewReference != null) { ImageView imageView = imageViewReference.get(); BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView); // Change bitmap only if this process is still associated with it // Or if we don't use any bitmap to task association (NO_DOWNLOADED_DRAWABLE mode) if ((this == bitmapDownloaderTask) || (mode != Mode.CORRECT)) { imageView.setImageBitmap(bitmap); } } } } /** * A fake Drawable that will be attached to the imageView while the download is in progress. * * <p>Contains a reference to the actual download task, so that a download task can be stopped * if a new binding is required, and makes sure that only the last started download process can * bind its result, independently of the download finish order.</p> */ static class DownloadedDrawable extends ColorDrawable { private final WeakReference<BitmapDownloaderTask> bitmapDownloaderTaskReference; public DownloadedDrawable(BitmapDownloaderTask bitmapDownloaderTask) { super(Color.TRANSPARENT); bitmapDownloaderTaskReference = new WeakReference<BitmapDownloaderTask>(bitmapDownloaderTask); } public BitmapDownloaderTask getBitmapDownloaderTask() { return bitmapDownloaderTaskReference.get(); } } /** * Mode.NO_ASYNC_TASK = Not async, generates NetworkOnMainThreadExc. * Mode.CORRECT = Async * @param mode N */ public void setMode(Mode mode) { this.mode = mode; clearCache(); } /* * Cache-related fields and methods. * * We use a hard and a soft cache. A soft reference cache is too aggressively cleared by the * Garbage Collector. */ private static final int HARD_CACHE_CAPACITY = 10; private static final int DELAY_BEFORE_PURGE = 10 * 1000; // in milliseconds // Hard cache, with a fixed maximum capacity and a life duration private final HashMap<String, Bitmap> sHardBitmapCache = new LinkedHashMap<String, Bitmap>( HARD_CACHE_CAPACITY / 2, 0.75f, true) { private static final long serialVersionUID = 4051027005566473991L; @Override protected boolean removeEldestEntry(LinkedHashMap.Entry<String, Bitmap> eldest) { if (size() > HARD_CACHE_CAPACITY) { // Entries push-out of hard reference cache are transferred to soft reference cache sSoftBitmapCache.put(eldest.getKey(), new SoftReference<Bitmap>(eldest.getValue())); return true; } else return false; } }; // Soft cache for bitmaps kicked out of hard cache private final static ConcurrentHashMap<String, SoftReference<Bitmap>> sSoftBitmapCache = new ConcurrentHashMap<String, SoftReference<Bitmap>>( HARD_CACHE_CAPACITY / 2); private final Handler purgeHandler = new Handler(); private final Runnable purger = new Runnable() { public void run() { clearCache(); } }; /** * Adds this bitmap to the cache. * @param bitmap The newly downloaded bitmap. */ private void addBitmapToCache(String url, Bitmap bitmap) { if (bitmap != null) { synchronized (sHardBitmapCache) { sHardBitmapCache.put(url, bitmap); } //Then cache to file...TODO addToFileCache(url, bitmap); } } /** * @param url The URL of the image that will be retrieved from the cache. * @return The cached bitmap or null if it was not found. */ private Bitmap getBitmapFromCache(String url) { // First try the hard reference cache synchronized (sHardBitmapCache) { final Bitmap bitmap = sHardBitmapCache.get(url); if (bitmap != null) { // Bitmap found in hard cache // Move element to first position, so that it is removed last sHardBitmapCache.remove(url); sHardBitmapCache.put(url, bitmap); return bitmap; } } // Then try the soft reference cache SoftReference<Bitmap> bitmapReference = sSoftBitmapCache.get(url); if (bitmapReference != null) { final Bitmap bitmap = bitmapReference.get(); if (bitmap != null) { // Bitmap found in soft cache return bitmap; } else { // Soft reference has been Garbage Collected sSoftBitmapCache.remove(url); } } //Then try from file...TODO Bitmap fromFile = getFromFileCache(url); if (fromFile != null) { return fromFile; } return null; } /** * Clears the image cache used internally to improve performance. Note that for memory * efficiency reasons, the cache will automatically be cleared after a certain inactivity delay. */ public void clearCache() { sHardBitmapCache.clear(); sSoftBitmapCache.clear(); } /** * Allow a new delay before the automatic cache clear is done. */ private void resetPurgeTimer() { purgeHandler.removeCallbacks(purger); purgeHandler.postDelayed(purger, DELAY_BEFORE_PURGE); } /* * From file */ private void addToFileCache(String url, Bitmap bitmap) { if (fileCache != null) { fileCache.put(fileCache.generateKeyFromURL(url), bitmap); } } private Bitmap getFromFileCache(String url) { if (fileCache != null) { return fileCache.getBitmap(fileCache.generateKeyFromURL(url)); } return null; } }