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/* * 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 com.example.android.imagedownloader;import android.app.ListActivity;import android.os.Bundle;import android.widget.RadioGroup;public class ImageListActivity extends ListActivity implements RadioGroup.OnCheckedChangeListener { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.imagelist); RadioGroup radioGroup = (RadioGroup) findViewById(R.id.radioGroup); radioGroup.setOnCheckedChangeListener(this); setListAdapter(new ImageAdapter()); } @Override protected void onStop() {// ((ImageAdapter) getListAdapter()).getImageDownloader().clearCache(); super.onStop(); } @Override public void onCheckedChanged(RadioGroup group, int checkedId) { ImageDownloader.Mode mode = ImageDownloader.Mode.NO_ASYNC_TASK; if (checkedId == R.id.correctButton) { mode = ImageDownloader.Mode.CORRECT; }else if (checkedId == R.id.randomButton) { mode = ImageDownloader.Mode.NO_DOWNLOADED_DRAWABLE; } ((ImageAdapter) getListAdapter()).getImageDownloader().setMode(mode); }} /* * 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 com.example.android.imagedownloader;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.ImageView;public class ImageAdapter extends BaseAdapter { private static final String[] URLS = { "http://lh5.ggpht.com/_mrb7w4gF8Ds/TCpetKSqM1I/AAAAAAAAD2c/Qef6Gsqf12Y/s144-c/_DSC4374%20copy.jpg", "http://lh5.ggpht.com/_Z6tbBnE-swM/TB0CryLkiLI/AAAAAAAAVSo/n6B78hsDUz4/s144-c/_DSC3454.jpg", "http://lh3.ggpht.com/_GEnSvSHk4iE/TDSfmyCfn0I/AAAAAAAAF8Y/cqmhEoxbwys/s144-c/_MG_3675.jpg", "http://lh6.ggpht.com/_Nsxc889y6hY/TBp7jfx-cgI/AAAAAAAAHAg/Rr7jX44r2Gc/s144-c/IMGP9775a.jpg", "http://lh3.ggpht.com/_lLj6go_T1CQ/TCD8PW09KBI/AAAAAAAAQdc/AqmOJ7eg5ig/s144-c/Juvenile%20Gannet%20despute.jpg", "http://lh6.ggpht.com/_ZN5zQnkI67I/TCFFZaJHDnI/AAAAAAAABVk/YoUbDQHJRdo/s144-c/P9250508.JPG", "http://lh4.ggpht.com/_XjNwVI0kmW8/TCOwNtzGheI/AAAAAAAAC84/SxFJhG7Scgo/s144-c/0014.jpg", "http://lh6.ggpht.com/_lnDTHoDrJ_Y/TBvKsJ9qHtI/AAAAAAAAG6g/Zll2zGvrm9c/s144-c/000007.JPG", "http://lh6.ggpht.com/_qvCl2efjxy0/TCIVI-TkuGI/AAAAAAAAOUY/vbk9MURsv48/s144-c/DSC_0844.JPG", "http://lh4.ggpht.com/_TPlturzdSE8/TBv4ugH60PI/AAAAAAAAMsI/p2pqG85Ghhs/s144-c/_MG_3963.jpg", "http://lh4.ggpht.com/_4f1e_yo-zMQ/TCe5h9yN-TI/AAAAAAAAXqs/8X2fIjtKjmw/s144-c/IMG_1786.JPG", "http://lh6.ggpht.com/_iFt5VZDjxkY/TB9rQyWnJ4I/AAAAAAAADpU/lP2iStizJz0/s144-c/DSCF1014.JPG", "http://lh5.ggpht.com/_hepKlJWopDg/TB-_WXikaYI/AAAAAAAAElI/715k4NvBM4w/s144-c/IMG_0075.JPG", "http://lh6.ggpht.com/_OfRSx6nn68g/TCzsQic_z3I/AAAAAAABOOI/5G4Kwzb2qhk/s144-c/EASTER%20ISLAND_Hanga%20Roa_31.5.08_46.JPG", "http://lh6.ggpht.com/_ZGv_0FWPbTE/TB-_GLhqYBI/AAAAAAABVxs/cVEvQzt0ke4/s144-c/IMG_1288_hf.jpg", "http://lh6.ggpht.com/_a29lGRJwo0E/TBqOK_tUKmI/AAAAAAAAVbw/UloKpjsKP3c/s144-c/31012332.jpg", "http://lh3.ggpht.com/_55Lla4_ARA4/TB6xbyxxJ9I/AAAAAAABTWo/GKe24SwECns/s144-c/Bluebird%20049.JPG", "http://lh3.ggpht.com/_iVnqmIBYi4Y/TCaOH6rRl1I/AAAAAAAA1qg/qeMerYQ6DYo/s144-c/Kwiat_100626_0016.jpg", "http://lh6.ggpht.com/_QFsB_q7HFlo/TCItd_2oBkI/AAAAAAAAFsk/4lgJWweJ5N8/s144-c/3705226938_d6d66d6068_o.jpg", "http://lh5.ggpht.com/_JTI0xxNrKFA/TBsKQ9uOGNI/AAAAAAAChQg/z8Exh32VVTA/s144-c/CRW_0015-composite.jpg", "http://lh6.ggpht.com/_loGyjar4MMI/S-InVNkTR_I/AAAAAAAADJY/Fb5ifFNGD70/s144-c/Moving%20Rock.jpg", "http://lh4.ggpht.com/_L7i4Tra_XRY/TBtxjScXLqI/AAAAAAAAE5o/ue15HuP8eWw/s144-c/opera%20house%20II.jpg", "http://lh3.ggpht.com/_rfAz5DWHZYs/S9cstBTv1iI/AAAAAAAAeYA/EyZPUeLMQ98/s144-c/DSC_6425.jpg", "http://lh6.ggpht.com/_iGI-XCxGLew/S-iYQWBEG-I/AAAAAAAACB8/JuFti4elptE/s144-c/norvig-polar-bear.jpg", "http://lh3.ggpht.com/_M3slUPpIgmk/SlbnavqG1cI/AAAAAAAACvo/z6-CnXGma7E/s144-c/mf_003.jpg", "http://lh4.ggpht.com/_loGyjar4MMI/S-InQvd_3hI/AAAAAAAADIw/dHvCFWfyHxQ/s144-c/Rainbokeh.jpg", "http://lh4.ggpht.com/_yy6KdedPYp4/SB5rpK3Zv0I/AAAAAAAAOM8/mokl_yo2c9E/s144-c/Point%20Reyes%20road%20.jpg", "http://lh5.ggpht.com/_6_dLVKawGJA/SMwq86HlAqI/AAAAAAAAG5U/q1gDNkmE5hI/s144-c/mobius-glow.jpg", "http://lh3.ggpht.com/_QFsB_q7HFlo/TCItc19Jw3I/AAAAAAAAFs4/nPfiz5VGENk/s144-c/4551649039_852be0a952_o.jpg", "http://lh6.ggpht.com/_TQY-Nm7P7Jc/TBpjA0ks2MI/AAAAAAAABcI/J6ViH98_poM/s144-c/IMG_6517.jpg", "http://lh3.ggpht.com/_rfAz5DWHZYs/S9cLAeKuueI/AAAAAAAAeYU/E19G8DOlJRo/s144-c/DSC_4397_8_9_tonemapped2.jpg", "http://lh4.ggpht.com/_TQY-Nm7P7Jc/TBpi6rKfFII/AAAAAAAABbg/79FOc0Dbq0c/s144-c/david_lee_sakura.jpg", "http://lh3.ggpht.com/_TQY-Nm7P7Jc/TBpi8EJ4eDI/AAAAAAAABb0/AZ8Cw1GCaIs/s144-c/Hokkaido%20Swans.jpg", "http://lh3.ggpht.com/_1aZMSFkxSJI/TCIjB6od89I/AAAAAAAACHM/CLWrkH0ziII/s144-c/079.jpg", "http://lh5.ggpht.com/_loGyjar4MMI/S-InWuHkR9I/AAAAAAAADJE/wD-XdmF7yUQ/s144-c/Colorado%20River%20Sunset.jpg", "http://lh3.ggpht.com/_0YSlK3HfZDQ/TCExCG1Zc3I/AAAAAAAAX1w/9oCH47V6uIQ/s144-c/3138923889_a7fa89cf94_o.jpg", "http://lh6.ggpht.com/_K29ox9DWiaM/TAXe4Fi0xTI/AAAAAAAAVIY/zZA2Qqt2HG0/s144-c/IMG_7100.JPG", "http://lh6.ggpht.com/_0YSlK3HfZDQ/TCEx16nJqpI/AAAAAAAAX1c/R5Vkzb8l7yo/s144-c/4235400281_34d87a1e0a_o.jpg", "http://lh4.ggpht.com/_8zSk3OGcpP4/TBsOVXXnkTI/AAAAAAAAAEo/0AwEmuqvboo/s144-c/yosemite_forrest.jpg", "http://lh4.ggpht.com/_6_dLVKawGJA/SLZToqXXVrI/AAAAAAAAG5k/7fPSz_ldN9w/s144-c/coastal-1.jpg", "http://lh4.ggpht.com/_WW8gsdKXVXI/TBpVr9i6BxI/AAAAAAABhNg/KC8aAJ0wVyk/s144-c/IMG_6233_1_2-2.jpg", "http://lh3.ggpht.com/_loGyjar4MMI/S-InS0tJJSI/AAAAAAAADHU/E8GQJ_qII58/s144-c/Windmills.jpg", "http://lh4.ggpht.com/_loGyjar4MMI/S-InbXaME3I/AAAAAAAADHo/4gNYkbxemFM/s144-c/Frantic.jpg", "http://lh5.ggpht.com/_loGyjar4MMI/S-InKAviXzI/AAAAAAAADHA/NkyP5Gge8eQ/s144-c/Rice%20Fields.jpg", "http://lh3.ggpht.com/_loGyjar4MMI/S-InZA8YsZI/AAAAAAAADH8/csssVxalPcc/s144-c/Seahorse.jpg", "http://lh3.ggpht.com/_syQa1hJRWGY/TBwkCHcq6aI/AAAAAAABBEg/R5KU1WWq59E/s144-c/Antelope.JPG", "http://lh5.ggpht.com/_MoEPoevCLZc/S9fHzNgdKDI/AAAAAAAADwE/UAno6j5StAs/s144-c/c84_7083.jpg", "http://lh4.ggpht.com/_DJGvVWd7IEc/TBpRsGjdAyI/AAAAAAAAFNw/rdvyRDgUD8A/s144-c/Free.jpg", "http://lh6.ggpht.com/_iO97DXC99NY/TBwq3_kmp9I/AAAAAAABcz0/apq1ffo_MZo/s144-c/IMG_0682_cp.jpg", "http://lh4.ggpht.com/_7V85eCJY_fg/TBpXudG4_PI/AAAAAAAAPEE/8cHJ7G84TkM/s144-c/20100530_120257_0273-Edit-2.jpg" }; private final ImageDownloader imageDownloader = new ImageDownloader(); public int getCount() { return URLS.length; } public String getItem(int position) { return URLS[position]; } public long getItemId(int position) { return URLS[position].hashCode(); } public View getView(int position, View view, ViewGroup parent) { if (view == null) { view = new ImageView(parent.getContext()); view.setPadding(6, 6, 6, 6); } imageDownloader.download(URLS[position], (ImageView) view); return view; } public ImageDownloader getImageDownloader() { return imageDownloader; }} /* * 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 com.example.android.imagedownloader;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 org.apache.http.impl.client.DefaultHttpClient;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.Handler;import android.util.Log;import android.widget.ImageView;import java.io.FilterInputStream;import java.io.IOException;import java.io.InputStream;import java.lang.ref.SoftReference;import java.lang.ref.WeakReference;import java.util.HashMap;import java.util.LinkedHashMap;import java.util.concurrent.ConcurrentHashMap;/** * This helper class download images from the Internet and binds those with the provided ImageView. * * 从网路下载图片并填充给指定的ImageView * * It requires the INTERNET permission, which should be added to your application's manifest * file. *
使用该类需要在manifest配置文件中添加 INTERNET 权限。 * * * A local cache of downloaded images is maintained internally to improve performance. *
会维护一份本地的cache以改善性能。 */public class ImageDownloader { private static final String LOG_TAG = "ImageDownloader"; public enum Mode { NO_ASYNC_TASK, NO_DOWNLOADED_DRAWABLE, 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 download(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 NO_DOWNLOADED_DRAWABLE: imageView.setMinimumHeight(156); BitmapDownloaderTask task = new BitmapDownloaderTask(imageView); task.execute(url); break; case CORRECT: 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; } 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 = (mode == Mode.NO_ASYNC_TASK) ? new DefaultHttpClient() : 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); return null; } final HttpEntity entity = response.getEntity(); if (entity != null) { InputStream inputStream = null; try { inputStream = entity.getContent(); // return BitmapFactory.decodeStream(inputStream); // Bug on slow connections, fixed in future release. return BitmapFactory.decodeStream(new FlushedInputStream(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(); } } 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 { private String url; private final WeakReference imageViewReference; public BitmapDownloaderTask(ImageView imageView) { imageViewReference = new WeakReference (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. * * 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.
*/ static class DownloadedDrawable extends ColorDrawable { private final WeakReference bitmapDownloaderTaskReference; public DownloadedDrawable(BitmapDownloaderTask bitmapDownloaderTask) { super(Color.BLACK); bitmapDownloaderTaskReference = new WeakReference (bitmapDownloaderTask); } public BitmapDownloaderTask getBitmapDownloaderTask() { return bitmapDownloaderTaskReference.get(); } } 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 sHardBitmapCache = new LinkedHashMap (HARD_CACHE_CAPACITY / 2, 0.75f, true) { @Override protected boolean removeEldestEntry(LinkedHashMap.Entry 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 (eldest.getValue())); return true; } else return false; } }; // Soft cache for bitmaps kicked out of hard cache private final static ConcurrentHashMap > sSoftBitmapCache = new ConcurrentHashMap >(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 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); } } 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); }}
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