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POblack screen appears when data loading takes long time in android
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  1. POblack screen appears when data loading takes long time in android
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    copied!<p>onCreateMethod of a Base class:</p> <pre><code>setListAdapter(new EfficientAdapter(this)); </code></pre> <p>Efficient Base Adapter class:</p> <pre><code> private class EfficientAdapter extends BaseAdapter { private LayoutInflater mInflater; Friends obj; Friends object; FriendsPictures pictureObject; ArrayList&lt;FriendsPictures&gt; arrayFriendsPictures; public EfficientAdapter(Context context) { // Cache the LayoutInflate to avoid asking for a new one each time. mInflater = LayoutInflater.from(context); } /** * The number of items in the list is determined by the number of speeches * in our array. * * @see android.widget.ListAdapter#getCount() */ public int getCount() { return arrFriendsObject.size(); } /** * Since the data comes from an array, just returning the index is * sufficent to get at the data. If we were using a more complex data * structure, we would return whatever object represents one row in the * list. * * @see android.widget.ListAdapter#getItem(int) */ public Object getItem(int position) { return position; } /** * Use the array index as a unique id. * * @see android.widget.ListAdapter#getItemId(int) */ public long getItemId(int position) { return position; } private final ImageDownloader imageDownloader = new ImageDownloader(); // private final DrawableManager drawable= new DrawableManager(); /** * Make a view to hold each row. * * @see android.widget.ListAdapter#getView(int, android.view.View, * android.view.ViewGroup) */ public View getView(int position, View convertView, ViewGroup parent) { // A ViewHolder keeps references to children views to avoid unneccessary calls // to findViewById() on each row. final ViewHolder holder; obj = arrFriendsObject.get(position); // When convertView is not null, we can reuse it directly, there is no need // to reinflate it. We only inflate a new View when the convertView supplied // by ListView is null. if (convertView == null) { convertView = mInflater.inflate(R.layout.Friendslistview, null); // Creates a ViewHolder and store references to the two children views // we want to bind data to. holder = new ViewHolder(); holder.text = (TextView) convertView.findViewById(R.id.FriendsText); holder.icon = (ImageView) convertView.findViewById(R.id.icon); convertView.setTag(holder); } else { // Get the ViewHolder back to get fast access to the TextView // and the ImageView. holder = (ViewHolder) convertView.getTag(); } // Bind the data efficiently with the holder. holder.text.setText(obj.FriendsTitle); // holder.icon.setImageBitmap((position &amp; 1) == 1 ? mIcon1 : mIcon2); // _mLoadImage = new GetImageAsyncTask(); // _mLoadImage.execute(urls[position]); object = new Friends(); object = arrFriendsObject.get(position); arrayFriendsPictures = new ArrayList&lt;FriendsPictures&gt;(); pictureObject = new FriendsPictures(); arrayFriendsPictures = object.arrFriendsPictures; pictureObject = arrayFriendsPictures.get(0); if(pictureObject.Image == null){ pictureObject.Image = imageDownloader.download(pictureObject.ImageUrl, (ImageView) holder.icon); // pictureObject.Image = drawable.fetchDrawableOnThread(pictureObject.ImageUrl, (ImageView) holder.icon); object.arrFriendsPictures.set(0,pictureObject); arrFriendsObject.set(position, object); } else { holder.icon.setImageBitmap(arrFriendsObject.get(position).arrFriendsPictures.get(0).Image); } // holder.icon.setBackgroundResource(R.drawable.photo1); convertView.setOnClickListener(mShowDetails); return convertView; } class ViewHolder { TextView text; ImageView icon; // ProgressBar showProgress; } } </code></pre> <p>ImageDownloader class:</p> <pre><code>public class ImageDownloader { private ProgressDialog dialog; private static final String LOG_TAG = "ImageDownloader"; public Bitmap download(String url, ImageView imageView) { resetPurgeTimer(); Bitmap bitmap = getBitmapFromCache(url); if (bitmap == null) { bitmap = forceDownload(url, imageView); } else { cancelPotentialDownload(url, imageView); imageView.setImageBitmap(bitmap); } return bitmap; } private Bitmap forceDownload(String url, ImageView imageView) { Bitmap bitmap = null; // State sanity: url is guaranteed to never be null in DownloadedDrawable and cache keys. if (url == null) { imageView.setImageDrawable(null); return null; } if (cancelPotentialDownload(url, imageView)) { BitmapDownloaderTask task = new BitmapDownloaderTask(imageView); DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task); imageView.setImageDrawable(downloadedDrawable); imageView.setMinimumHeight(156); task.execute(url); try { bitmap = task.get(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ExecutionException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return bitmap; } 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; } 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 = new DefaultHttpClient(); 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 { } return null; } static class FlushedInputStream extends FilterInputStream { public FlushedInputStream(InputStream inputStream) { super(inputStream); } @Override public long skip(long n) throws IOException { long totalBytesSkipped = 0L; while (totalBytesSkipped &lt; n) { long bytesSkipped = in.skip(n - totalBytesSkipped); if (bytesSkipped == 0L) { int b = read(); if (b &lt; 0) { break; // we reached EOF } else { bytesSkipped = 1; // we read one byte } } totalBytesSkipped += bytesSkipped; } return totalBytesSkipped; } } public class BitmapDownloaderTask extends AsyncTask&lt;String, Void, Bitmap&gt; { private String url; Bitmap bitmap; private final WeakReference&lt;ImageView&gt; imageViewReference; public BitmapDownloaderTask(ImageView imageView) { imageViewReference = new WeakReference&lt;ImageView&gt;(imageView); } @Override // can use UI thread here protected void onPreExecute() { if(dialog!=null) { dialog.setMessage("loading.."); dialog.show(); } } @Override protected Bitmap doInBackground(String... params) { url = params[0]; return downloadBitmap(url); } @Override protected void onPostExecute(Bitmap bitmap) { if (isCancelled()) { bitmap = null; } if(dialog!=null) { dialog.dismiss(); } 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)) { imageView.setImageBitmap(bitmap); } } } } static class DownloadedDrawable extends ColorDrawable { private final WeakReference&lt;BitmapDownloaderTask&gt; bitmapDownloaderTaskReference; public DownloadedDrawable(BitmapDownloaderTask bitmapDownloaderTask) { super(Color.BLACK); bitmapDownloaderTaskReference = new WeakReference&lt;BitmapDownloaderTask&gt;(bitmapDownloaderTask); } public BitmapDownloaderTask getBitmapDownloaderTask() { return bitmapDownloaderTaskReference.get(); } } 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&lt;String, Bitmap&gt; sHardBitmapCache = new LinkedHashMap&lt;String, Bitmap&gt;(HARD_CACHE_CAPACITY / 2, 0.75f, true) { @Override protected boolean removeEldestEntry(LinkedHashMap.Entry&lt;String, Bitmap&gt; eldest) { if (size() &gt; HARD_CACHE_CAPACITY) { // Entries push-out of hard reference cache are transferred to soft reference cache sSoftBitmapCache.put(eldest.getKey(), new SoftReference&lt;Bitmap&gt;(eldest.getValue())); return true; } else return false; } }; // Soft cache for bitmaps kicked out of hard cache private final static ConcurrentHashMap&lt;String, SoftReference&lt;Bitmap&gt;&gt; sSoftBitmapCache = new ConcurrentHashMap&lt;String, SoftReference&lt;Bitmap&gt;&gt;(HARD_CACHE_CAPACITY / 2); private final Handler purgeHandler = new Handler(); private final Runnable purger = new Runnable() { public void run() { clearCache(); } }; private void addBitmapToCache(String url, Bitmap bitmap) { if (bitmap != null) { synchronized (sHardBitmapCache) { sHardBitmapCache.put(url, bitmap); } } } 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&lt;Bitmap&gt; 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; } public void clearCache() { sHardBitmapCache.clear(); sSoftBitmapCache.clear(); } private void resetPurgeTimer() { purgeHandler.removeCallbacks(purger); purgeHandler.postDelayed(purger, DELAY_BEFORE_PURGE); } } </code></pre>
 

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