Java tutorial
package com.chinaLife.claimAssistant.tools; /* * 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.File; 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.ArrayList; import java.util.HashMap; import java.util.LinkedHashMap; import java.util.List; import java.util.concurrent.ConcurrentHashMap; 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.message.BasicNameValuePair; import com.chinaLife.claimAssistant.R; import com.chinaLife.claimAssistant.thread.sc_RequestServerFromHttp; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Color; import android.graphics.drawable.BitmapDrawable; 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; /** * 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 sc_ImageDownloaderId { private static final String LOG = "ImageDownloader"; int connection_count = 0; int connection_count_totle = 0; Context context; Bitmap bitmap = null; int resid = R.drawable.sc_icon_default_photo; public sc_ImageDownloaderId(Context context, int connection_count_totle) { this.context = context; this.connection_count_totle = connection_count_totle; } public sc_ImageDownloaderId(Context context, int resid, int connection_count_totle) { this.context = context; this.resid = resid; this.connection_count_totle = connection_count_totle; } /** * Allow a new delay before the automatic cache clear is done. */ private void resetPurgeTimer() { purgeHandler.removeCallbacks(purger); purgeHandler.postDelayed(purger, DELAY_BEFORE_PURGE); } /** * 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(File file, String id, ImageView imageView) { resetPurgeTimer(); // ? Bitmap bitmap = getBitmapFromCache(file.getAbsolutePath()); if (id == null || id.trim().equals("") || id.trim().equals("0")) { return; } if (connection_count > connection_count_totle) { return; } if (bitmap == null) { System.out.println("1"); forceDownload(file, id, imageView); } else { System.out.println("2"); cancelPotentialDownload(file.getAbsolutePath(), 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(File file, String id, ImageView imageView) { // State sanity: url is guaranteed to never be null in // DownloadedDrawable and cache keys. if (file.getAbsolutePath() == null) { // imageView.setImageResource(resid); return; } Log.i("", imageView.toString() + "-----" + file.getAbsolutePath()); if (cancelPotentialDownload(file.getAbsolutePath(), imageView)) { BitmapDownloaderTask task = new BitmapDownloaderTask(imageView); DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task, context, resid); imageView.setImageDrawable(downloadedDrawable); task.execute(file, id); } } /** * 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 filename, ImageView imageView) { BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView); if (bitmapDownloaderTask != null) { String bitmapUrl = bitmapDownloaderTask.filename; if ((bitmapUrl == null) || (!bitmapUrl.equals(filename))) { 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) { System.out.println("uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu"); if (imageView != null) { Drawable drawable = imageView.getDrawable(); if (drawable instanceof DownloadedDrawable) { DownloadedDrawable downloadedDrawable = (DownloadedDrawable) drawable; return downloadedDrawable.getBitmapDownloaderTask(); } } return null; } public Bitmap downloadBitmap(File file, String id) { System.out.println("1"); Bitmap bitmap = null; if (file.exists() && file.isFile()) { try { bitmap = sc_CommonUtils.getDrawable(file.getAbsolutePath(), null); } catch (Exception e) { } if (bitmap != null) { return bitmap; } } System.out.println("2"); connection_count++; boolean b = sc_RequestServerFromHttp.downloadPhoto(file, id); System.out.println("3"); connection_count--; if (b) { try { bitmap = sc_CommonUtils.getDrawable(file.getAbsolutePath(), null); } catch (Exception e) { } } return bitmap; } /* * 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<Object, Void, Bitmap> { private String filename; private final WeakReference<ImageView> imageViewReference; public BitmapDownloaderTask(ImageView imageView) { imageViewReference = new WeakReference<ImageView>(imageView); } /** * Actual download method. */ @Override protected Bitmap doInBackground(Object... params) { filename = ((File) params[0]).getAbsolutePath(); Bitmap b = downloadBitmap((File) params[0], (String) params[1]); System.out.println("----------------------------------------------"); return b; } /** * Once the image is downloaded, associates it to the imageView */ @Override protected void onPostExecute(Bitmap bitmap) { if (isCancelled()) { bitmap = null; } if (bitmap == null) { return; } addBitmapToCache(filename, bitmap); if (imageViewReference != null) { ImageView imageView = imageViewReference.get(); if (imageView == null) return; BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView); // Change bitmap only if this process is still associated with // it if ((this == bitmapDownloaderTask && bitmap != null)) { imageView.setImageBitmap(bitmap); } else { // imageView.setImageResource(resid); } } } } /** * 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, Context context, int resid) { super(BitmapFactory.decodeResource(context.getResources(), resid)); bitmapDownloaderTaskReference = new WeakReference<BitmapDownloaderTask>(bitmapDownloaderTask); } public BitmapDownloaderTask getBitmapDownloaderTask() { return bitmapDownloaderTaskReference.get(); } } public void setMode() { 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) { @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) { // 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(); } }