Java tutorial
/** * Copyright (C) 2012 Picon software * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ package fr.eoit.util; import java.io.*; import java.lang.ref.WeakReference; import java.util.HashMap; import java.util.Map.Entry; import android.content.Context; import android.content.res.Resources; import android.graphics.Bitmap; import android.graphics.Bitmap.CompressFormat; import android.graphics.BitmapFactory; import android.graphics.drawable.BitmapDrawable; import android.graphics.drawable.Drawable; import android.net.http.AndroidHttpClient; import android.os.AsyncTask; import android.support.v4.util.LruCache; import android.util.Log; import android.widget.ImageView; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.HttpStatus; import org.apache.http.client.methods.HttpGet; import fr.eoit.BuildConfig; import fr.eoit.R; /** * 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 ImageDownloader { private static final String LOG_TAG = "ImageDownloader"; private static final String cacheFileName = "eoit.icn.cache"; // Hard cache, with a fixed maximum capacity and a life duration int cacheSize = 4 * 1024 * 1024; // 4MiB LruCache<String, Bitmap> sHardBitmapCache = new LruCache<String, Bitmap>(cacheSize) { @Override protected int sizeOf(String key, Bitmap value) { return value.getRowBytes() * value.getHeight(); } }; @SuppressWarnings("unchecked") public void loadImageCache(Context context) { if (BuildConfig.DEBUG) Log.v(LOG_TAG, "Loading image cache..."); File cacheFile = new File(context.getCacheDir(), cacheFileName); if (cacheFile.exists() && cacheFile.length() > 0) { ObjectInputStream ois = null; try { HashMap<String, String> cacheDescription = new HashMap<String, String>(); ois = new ObjectInputStream(new FileInputStream(cacheFile)); cacheDescription = (HashMap<String, String>) ois.readObject(); for (Entry<String, String> cacheDescEntry : cacheDescription.entrySet()) { loadSingleCacheFile(cacheDescEntry.getKey(), context); } } catch (StreamCorruptedException e) { Log.e(LOG_TAG, e.getMessage(), e); } catch (FileNotFoundException e) { Log.e(LOG_TAG, e.getMessage(), e); } catch (EOFException e) { //delete the corrupted cache file Log.w(LOG_TAG, "Deleting the corrupted cache file.", e); cacheFile.delete(); } catch (IOException e) { Log.e(LOG_TAG, e.getMessage(), e); } catch (ClassNotFoundException e) { Log.e(LOG_TAG, e.getMessage(), e); } finally { if (ois != null) { try { ois.close(); } catch (IOException e) { Log.e(LOG_TAG, e.getMessage(), e); } } } } } private Bitmap loadSingleCacheFile(String url, Context context) { Bitmap bitmap = null; File cacheIconFile = new File(context.getCacheDir(), getCacheFileName(url)); if (cacheIconFile.exists()) { if (BuildConfig.DEBUG) Log.v(LOG_TAG, "Loading cache file : " + url); bitmap = BitmapFactory.decodeFile(cacheIconFile.getAbsolutePath()); if (bitmap != null) { sHardBitmapCache.put(url, bitmap); } } return bitmap; } private void flushSingleCacheFileToDisk(Bitmap bitmap, String cacheIconName, Context context) throws IOException { File cacheIconFile = new File(context.getCacheDir(), cacheIconName); if (!cacheIconFile.exists()) { if (BuildConfig.DEBUG) Log.v(LOG_TAG, "Flushing bitmap " + cacheIconName + " to disk..."); cacheIconFile.createNewFile(); BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(cacheIconFile)); bitmap.compress(CompressFormat.PNG, 100, bos); bos.flush(); bos.close(); } } private String getCacheFileName(String key) { return key.replaceAll("/", "").replaceAll(":", "").replaceAll("\\.", "") + ".cache"; } /** * 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 download(String url, ImageView imageView) { download(url, imageView, null); } /** * Same as {@link #download(String, ImageView)}, with the possibility to provide an additional * cookie that will be used when the image will be retrieved. * * @param url The URL of the image to download. * @param imageView The ImageView to bind the downloaded image to. * @param cookie A cookie String that will be used by the http connection. */ public void download(String url, ImageView imageView, String cookie) { Bitmap bitmap = getBitmapFromCache(url, imageView.getContext()); if (bitmap == null) { forceDownload(url, imageView, cookie); } 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, String cookie) { // 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)) { BitmapDownloaderTask task = new BitmapDownloaderTask(imageView); DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task, imageView.getContext().getResources()); imageView.setImageDrawable(downloadedDrawable); task.execute(url, cookie); } } /** * 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.evictAll(); } /** * 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; } /** * @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. */ Bitmap getBitmapFromCache(String url, Context context) { return sHardBitmapCache.get(url); } /** * The actual AsyncTask that will asynchronously download the image. */ class BitmapDownloaderTask extends AsyncTask<String, Void, Bitmap> { private static final int IO_BUFFER_SIZE = 4 * 1024; 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]; Context context = null; if (imageViewReference.get() != null) { context = imageViewReference.get().getContext(); Bitmap cacheBitmap = loadSingleCacheFile(url, context); if (cacheBitmap != null) { return cacheBitmap; } } final AndroidHttpClient client = AndroidHttpClient.newInstance("Android"); final HttpGet getRequest = new HttpGet(url); String cookie = params[1]; if (cookie != null) { getRequest.setHeader("cookie", cookie); } try { HttpResponse response = client.execute(getRequest); final int statusCode = response.getStatusLine().getStatusCode(); if (statusCode != HttpStatus.SC_OK) { Log.w("ImageDownloader", "Error " + statusCode + " while retrieving bitmap from " + url); return null; } final HttpEntity entity = response.getEntity(); if (entity != null) { InputStream inputStream = null; try { inputStream = entity.getContent(); final Bitmap bitmap = BitmapFactory.decodeStream(inputStream); if (context != null) { flushSingleCacheFileToDisk(bitmap, getCacheFileName(url), context); } return bitmap; } finally { if (inputStream != null) { inputStream.close(); } //if (outputStream != null) { // outputStream.close(); //} entity.consumeContent(); } } } catch (IOException e) { getRequest.abort(); Log.w(LOG_TAG, "I/O error while retrieving bitmap from " + url, e); } catch (IllegalStateException e) { getRequest.abort(); Log.w(LOG_TAG, "Incorrect URL: " + url); } catch (Exception e) { getRequest.abort(); Log.w(LOG_TAG, "Error while retrieving bitmap from " + url, e); } finally { if (client != null) { client.close(); } } return null; } /** * Once the image is downloaded, associates it to the imageView */ @Override protected void onPostExecute(Bitmap bitmap) { if (isCancelled()) { bitmap = null; } // Add bitmap to cache if (bitmap != null) { sHardBitmapCache.put(url, bitmap); } if (imageViewReference != null) { ImageView imageView = imageViewReference.get(); BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView); // Change bitmap only if this process is still associated with it if (this == bitmapDownloaderTask) { imageView.setImageBitmap(bitmap); } } } public void copy(InputStream in, OutputStream out) throws IOException { byte[] b = new byte[IO_BUFFER_SIZE]; int read; while ((read = in.read(b)) != -1) { out.write(b, 0, read); } } } /** * 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 BitmapDrawable { private final WeakReference<BitmapDownloaderTask> bitmapDownloaderTaskReference; public DownloadedDrawable(BitmapDownloaderTask bitmapDownloaderTask, Resources resources) { super(resources, BitmapFactory.decodeResource(resources, R.drawable.unknown)); bitmapDownloaderTaskReference = new WeakReference<BitmapDownloaderTask>(bitmapDownloaderTask); } public BitmapDownloaderTask getBitmapDownloaderTask() { return bitmapDownloaderTaskReference.get(); } } }