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POandroid lazy loading not showing images on phone or showing and is slow
 

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  1. POandroid lazy loading not showing images on phone or showing and is slow
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    <p>I am using JSON to parse an online xml document and also 2 methods for lazy image loading. Below is my source code, explanation and my problem:</p> <p>Explanation:</p> <p>Method 1: Use <code>AsyncTask</code> and line <code>imageLoader.DisplayImage((String)jsonImageText.get("imageLink"), activity, imageView);</code> inside the adapter.</p> <p>Method 2:</p> <p>Not use <code>AsyncTask</code> and use the rest of the try-catch block and NOT the line <code>imageLoader.DisplayImage((String)jsonImageText.get("imageLink"), activity, imageView);</code></p> <p>The problems:</p> <p>Method 1: </p> <p>The images are displayed on the emulator and the loading is pretty fast, but they fail to display on a phone or a tablet.</p> <p>Method 2:</p> <p>The images are displayed on all the emulators and real devices, but the loading and scrolling are very slow.</p> <p>Is there any way to fix either of these 2 methods or even both?</p> <p>This is the list adapter which returns the ListView's row view:</p> <pre><code>public class RssListAdapter extends ArrayAdapter&lt;JSONObject&gt; { public ImageLoader imageLoader; public RssListAdapter(Activity activity, List&lt;JSONObject&gt; imageAndTexts) { super(activity, 0, imageAndTexts); imageLoader=new ImageLoader(activity.getApplicationContext()); } @Override public View getView(int position, View convertView, ViewGroup parent) { Activity activity = (Activity) getContext(); LayoutInflater inflater = activity.getLayoutInflater(); // Inflate the views from XML View rowView = inflater.inflate(R.layout.image_text_layout, null); JSONObject jsonImageText = getItem(position); TextView textView = (TextView) rowView.findViewById(R.id.job_text); ImageView imageView = (ImageView) rowView.findViewById(R.id.feed_image); try { if (jsonImageText.get("imageLink") != null){ System.out.println("XXXX Link found!"); String url = (String) jsonImageText.get("imageLink"); URL feedImage= new URL(url); HttpURLConnection conn= (HttpURLConnection)feedImage.openConnection(); InputStream is = conn.getInputStream(); Bitmap img = BitmapFactory.decodeStream(is); imageView.setImageBitmap(img); //imageLoader.DisplayImage((String)jsonImageText.get("imageLink"), activity, imageView); } Spanned text = (Spanned)jsonImageText.get("text"); textView.setText(text); } catch (MalformedURLException e) { textView.setText("JSON Exception"); } catch (IOException e) { textView.setText("JSON Exception"); } catch (JSONException e) { textView.setText("JSON Exception"); } return rowView; } } </code></pre> <p>This is the ImageLoader class:</p> <pre><code>public class ImageLoader { MemoryCache memoryCache=new MemoryCache(); FileCache fileCache; private Map&lt;ImageView, String&gt; imageViews=Collections.synchronizedMap(new WeakHashMap&lt;ImageView, String&gt;()); public ImageLoader(Context context){ //Make the background thread low priority. This way it will not affect the UI performance photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1); fileCache=new FileCache(context); } final int stub_id=R.drawable.icon; public void DisplayImage(String url, Activity activity, ImageView imageView) { imageViews.put(imageView, url); Bitmap bitmap=memoryCache.get(url); if(bitmap!=null) imageView.setImageBitmap(bitmap); else { queuePhoto(url, activity, imageView); imageView.setImageResource(stub_id); } } private void queuePhoto(String url, Activity activity, ImageView imageView) { //This ImageView may be used for other images before. So there may be some old tasks in the queue. We need to discard them. photosQueue.Clean(imageView); PhotoToLoad p=new PhotoToLoad(url, imageView); synchronized(photosQueue.photosToLoad){ photosQueue.photosToLoad.push(p); photosQueue.photosToLoad.notifyAll(); } //start thread if it's not started yet if(photoLoaderThread.getState()==Thread.State.NEW) photoLoaderThread.start(); } private Bitmap getBitmap(String url) { File f=fileCache.getFile(url); //from SD cache Bitmap b = decodeFile(f); if(b!=null) return b; //from web try { Bitmap bitmap=null; URL imageUrl = new URL(url); HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection(); conn.setConnectTimeout(30000); conn.setReadTimeout(30000); InputStream is=conn.getInputStream(); OutputStream os = new FileOutputStream(f); Utils.CopyStream(is, os); os.close(); bitmap = decodeFile(f); return bitmap; } catch (Exception ex){ ex.printStackTrace(); 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; int width_tmp=o.outWidth, height_tmp=o.outHeight; int scale=1; while(true){ if(width_tmp/2&lt;REQUIRED_SIZE || height_tmp/2&lt;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; } //Task for the queue private class PhotoToLoad { public String url; public ImageView imageView; public PhotoToLoad(String u, ImageView i){ url=u; imageView=i; } } PhotosQueue photosQueue=new PhotosQueue(); public void stopThread() { photoLoaderThread.interrupt(); } //stores list of photos to download class PhotosQueue { private Stack&lt;PhotoToLoad&gt; photosToLoad=new Stack&lt;PhotoToLoad&gt;(); //removes all instances of this ImageView public void Clean(ImageView image) { for(int j=0 ;j&lt;photosToLoad.size();){ if(photosToLoad.get(j).imageView==image) photosToLoad.remove(j); else ++j; } } } class PhotosLoader extends Thread { public void run() { try { while(true) { //thread waits until there are any images to load in the queue if(photosQueue.photosToLoad.size()==0) synchronized(photosQueue.photosToLoad){ photosQueue.photosToLoad.wait(); } if(photosQueue.photosToLoad.size()!=0) { PhotoToLoad photoToLoad; synchronized(photosQueue.photosToLoad){ photoToLoad=photosQueue.photosToLoad.pop(); } Bitmap bmp=getBitmap(photoToLoad.url); memoryCache.put(photoToLoad.url, bmp); String tag=imageViews.get(photoToLoad.imageView); if(tag!=null &amp;&amp; tag.equals(photoToLoad.url)){ BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad.imageView); Activity a=(Activity)photoToLoad.imageView.getContext(); a.runOnUiThread(bd); } } if(Thread.interrupted()) break; } } catch (InterruptedException e) { //allow thread to exit } } } PhotosLoader photoLoaderThread=new PhotosLoader(); //Used to display bitmap in the UI thread class BitmapDisplayer implements Runnable { Bitmap bitmap; ImageView imageView; public BitmapDisplayer(Bitmap b, ImageView i){bitmap=b;imageView=i;} public void run() { if(bitmap!=null) imageView.setImageBitmap(bitmap); else imageView.setImageResource(stub_id); } } public void clearCache() { memoryCache.clear(); fileCache.clear(); } } </code></pre>
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    1. COYour first line "JSON to parse an online xml document", something new that i heard.
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      1. USParesh Mayani
    2. COI tried using DOM, but there was a problem with the double quotes ", the parser on the emulator failed.
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    3. COI've changed my parser and now it uses XmlPull.
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