Java tutorial
/* * 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. */ package cat.joronya.utils.image; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.HttpStatus; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import cat.joronya.utils.file.FileUtils; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Color; import android.graphics.drawable.ColorDrawable; import android.graphics.drawable.Drawable; import android.net.http.AndroidHttpClient; import android.os.AsyncTask; import android.os.Environment; import android.os.Handler; import android.util.Log; import android.widget.ImageView; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.FilterInputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.lang.ref.SoftReference; import java.lang.ref.WeakReference; import java.net.MalformedURLException; import java.net.URL; import java.util.HashMap; import java.util.HashSet; import java.util.LinkedHashMap; import java.util.concurrent.ConcurrentHashMap; /** * 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"; public static String CACHE_DIR = "JoronyaUtils"; private File cacheDir; private Context context; private int requiredSize = 70; protected HashSet<String> notFounds = new HashSet<String>(); private Drawable defaultDrawable; public ImageDownloader(Context context, String cachedir, String subdir, int requiredSize) { this.context = context; this.requiredSize = requiredSize; File firstCacheDir = null; if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { if (cachedir == null && "".equals(cachedir)) firstCacheDir = new File(Environment.getExternalStorageDirectory(), CACHE_DIR); else firstCacheDir = new File(Environment.getExternalStorageDirectory(), cachedir); } else { firstCacheDir = context.getCacheDir(); } // el sub cache dir cacheDir = new File(firstCacheDir, subdir); if (!cacheDir.exists()) cacheDir.mkdirs(); // preparem fitxer ".nomedia", pq el MediaScanner no trobi els fitxers File nomediaFile = new File(cacheDir, ".nomedia"); if (!nomediaFile.exists()) try { nomediaFile.createNewFile(); } catch (IOException e) { } } /** * 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, Drawable defaultDrawable) { this.defaultDrawable = defaultDrawable; resetPurgeTimer(); // esta a notFounds? if (notFounds.contains(url)) { imageView.setImageDrawable(defaultDrawable); return; } 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(defaultDrawable); return; } if (cancelPotentialDownload(url, imageView)) { BitmapDownloaderTask task = new BitmapDownloaderTask(imageView); DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task); imageView.setImageDrawable(downloadedDrawable); imageView.setMinimumHeight(156); task.execute(url); } } /** * 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; } @SuppressWarnings("unused") Bitmap downloadBitmap(String url) { final int IO_BUFFER_SIZE = 4 * 1024; // AndroidHttpClient is not allowed to be used from the main thread final HttpClient client = AndroidHttpClient.newInstance("Android"); final HttpGet getRequest = new HttpGet(url); 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); // registrem el 404 notFounds.add(url); return null; } final HttpEntity entity = response.getEntity(); if (entity != null) { InputStream inputStream = null; try { inputStream = entity.getContent(); // return BitmapFactory.decodeStream(inputStream); URL theURL = null; try { theURL = new URL(url); } catch (MalformedURLException e) { Log.d(LOG_TAG, "Image URL malformed"); // registrem el 404 notFounds.add(url); return null; } String[] filename = theURL.getFile().split("/"); File f = new File(cacheDir, filename[filename.length - 1]); // store in SD OutputStream os = new FileOutputStream(f); FileUtils.CopyStream(new FlushedInputStream(inputStream), os); os.close(); // torno a inicialitzar l'stream inputStream = new FileInputStream(f); // trobat, treiem del notfounds notFounds.remove(url); // Bug on slow connections, fixed in future release. //return BitmapFactory.decodeStream(new FlushedInputStream(inputStream)); return BitmapFactory.decodeStream(inputStream); } finally { if (inputStream != null) { inputStream.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 instanceof AndroidHttpClient)) { ((AndroidHttpClient) client).close(); } } // registrem el 404 notFounds.add(url); return null; } /* * 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) { if (bitmap != null) { imageView.setImageBitmap(bitmap); } else { imageView.setImageDrawable(defaultDrawable); } } } } } /** * 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.WHITE); bitmapDownloaderTaskReference = new WeakReference<BitmapDownloaderTask>(bitmapDownloaderTask); } public BitmapDownloaderTask getBitmapDownloaderTask() { return bitmapDownloaderTaskReference.get(); } } /* * 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 @SuppressWarnings("serial") private final HashMap<String, Bitmap> sHardBitmapCache = new LinkedHashMap<String, Bitmap>( HARD_CACHE_CAPACITY / 2, 0.75f, true) { @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); } } } /** * @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) { // found, remove from notfounds notFounds.remove(url); // Bitmap found in soft cache return bitmap; } else { // Soft reference has been Garbage Collected sSoftBitmapCache.remove(url); } } // otherwise try disk cache, no sabem el filename i guardem un hash URL theURL = null; try { theURL = new URL(url); } catch (MalformedURLException e) { Log.d(LOG_TAG, "Image URL malformed"); // registrem el 404 notFounds.add(url); return null; } String[] filename = theURL.getFile().split("/"); File f = new File(cacheDir, filename[filename.length - 1]); //from SD cache Bitmap b = decodeFile(f); if (b != null) { // guardem fitxer a cache Log.d(LOG_TAG, "Image found in SD cache and loaded: " + filename); // afegim a la cache per proxims usos addBitmapToCache(url, b); // if url found, remove url from notfounds notFounds.remove(url); // retornat return b; } // registrem el 404 notFounds.add(url); return null; } //decodes image and scales it to reduce memory consumption private Bitmap decodeFile(File f) { try { //decode image size BitmapFactory.Options o = new BitmapFactory.Options(); o.inJustDecodeBounds = true; BitmapFactory.decodeStream(new FileInputStream(f), null, o); //Find the correct scale value. It should be the power of 2. //final int REQUIRED_SIZE=70; final int REQUIRED_SIZE = requiredSize; int width_tmp = o.outWidth, height_tmp = o.outHeight; int scale = 1; while (true) { if (width_tmp / 2 < REQUIRED_SIZE || height_tmp / 2 < REQUIRED_SIZE) break; width_tmp /= 2; height_tmp /= 2; scale *= 2; } //decode with inSampleSize BitmapFactory.Options o2 = new BitmapFactory.Options(); o2.inSampleSize = scale; return BitmapFactory.decodeStream(new FileInputStream(f), null, o2); } catch (FileNotFoundException e) { } 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); } }