Images not being cached locally (using Universal Image Loader) - slow image load times

Question

Description of the problem: I\'m creating a scrollable list of articles with thumbnails that\'s populated by my SQLite database. In general, it\'s \"workin

Answer 1

This class worked for me:

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Map;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.HttpVersion;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.CoreProtocolPNames;
import org.apache.http.params.HttpParams;

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.os.AsyncTask;
import android.util.Log;
import android.widget.ImageView;

public class ImageDownloader {

    Map imageCache;

    public ImageDownloader(){
        imageCache = new HashMap();

    }

    //download function
    public void download(String url, ImageView imageView) {
         if (cancelPotentialDownload(url, imageView)&&url!=null) {

             //Caching code right here
             String filename = String.valueOf(url.hashCode());
             File f = new File(getCacheDirectory(imageView.getContext()), filename);

              // Is the bitmap in our memory cache?
             Bitmap bitmap = null;

              bitmap = (Bitmap)imageCache.get(f.getPath());
                BitmapFactory.Options bfOptions=new BitmapFactory.Options();
                bfOptions.inDither=false;                     //Disable Dithering mode
                bfOptions.inPurgeable=true;                   //Tell to gc that whether it needs free memory, the Bitmap can be cleared
                bfOptions.inInputShareable=true;              //Which kind of reference will be used to recover the Bitmap data after being clear, when it will be used in the future
                bfOptions.inTempStorage=new byte[32 * 1024]; 
                FileInputStream fs=null;

              if(bitmap == null){

                  //bitmap = BitmapFactory.decodeFile(f.getPath(),options);
                  try {
                      fs = new FileInputStream(f);
                        if(fs!=null) bitmap=BitmapFactory.decodeFileDescriptor(fs.getFD(), null, bfOptions);
                    } catch (IOException e) {
                        //TODO do something intelligent
                        e.printStackTrace();
                    } finally{ 
                        if(fs!=null) {
                            try {
                                fs.close();
                            } catch (IOException e) {
                                // TODO Auto-generated catch block
                                e.printStackTrace();
                            }
                        }
                    }

                  if(bitmap != null){
                      imageCache.put(f.getPath(), bitmap);
                  }

              }
              //No? download it
              if(bitmap == null){
                  BitmapDownloaderTask task = new BitmapDownloaderTask(imageView);
                  DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task);
                  imageView.setImageDrawable(downloadedDrawable);
                  task.execute(url);
              }else{
                  //Yes? set the image
                  imageView.setImageBitmap(bitmap);
              }
         }
    }

    //cancel a download (internal only)
    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;
    }

    //gets an existing download if one exists for the imageview
    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;
    }

    //our caching functions
    // Find the dir to save cached images
    public static File getCacheDirectory(Context context){
        String sdState = android.os.Environment.getExternalStorageState();
        File cacheDir;

        if (sdState.equals(android.os.Environment.MEDIA_MOUNTED)) {
            File sdDir = android.os.Environment.getExternalStorageDirectory();  

            //TODO : Change your diretcory here
            cacheDir = new File(sdDir,"data/tac/images");
        }
        else
            cacheDir = context.getCacheDir();

        if(!cacheDir.exists())
            cacheDir.mkdirs();
            return cacheDir;
    }

    private void writeFile(Bitmap bmp, File f) {
          FileOutputStream out = null;

          try {
            out = new FileOutputStream(f);
            bmp.compress(Bitmap.CompressFormat.PNG, 80, out);
          } catch (Exception e) {
            e.printStackTrace();
          }
          finally { 
            try { if (out != null ) out.close(); }
            catch(Exception ex) {} 
          }
    }
    ///////////////////////

    //download asynctask
    public class BitmapDownloaderTask extends AsyncTask {
        private String url;
        private final WeakReference imageViewReference;

        public BitmapDownloaderTask(ImageView imageView) {
            imageViewReference = new WeakReference(imageView);
        }

        @Override
        // Actual download method, run in the task thread
        protected Bitmap doInBackground(String... params) {
             // params comes from the execute() call: params[0] is the url.
             url = (String)params[0];
             return downloadBitmap(params[0]);
        }

        @Override
        // Once the image is downloaded, associates it to the imageView
        protected void onPostExecute(Bitmap bitmap) {
            if (isCancelled()) {
                bitmap = null;
            }

            if (imageViewReference != null) {
                ImageView imageView = imageViewReference.get();
                BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView);
                // Change bitmap only if this process is still associated with it
                if (this == bitmapDownloaderTask) {
                    imageView.setImageBitmap(bitmap);

                    //cache the image


                    String filename = String.valueOf(url.hashCode());
                    File f = new File(getCacheDirectory(imageView.getContext()), filename);

                    imageCache.put(f.getPath(), bitmap);

                    writeFile(bitmap, f);
                }
            }
        }


    }

    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();
        }
    }

    //the actual download code
    static Bitmap downloadBitmap(String url) {
        HttpParams params = new BasicHttpParams();
        params.setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1);
        HttpClient client = new DefaultHttpClient(params);
        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(); 
                    final Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                    return bitmap;
                } finally {
                    if (inputStream != null) {
                        inputStream.close();  
                    }
                    entity.consumeContent();
                }
            }
        } catch (Exception e) {
            // Could provide a more explicit error message for IOException or IllegalStateException
            getRequest.abort();
            Log.w("ImageDownloader", "Error while retrieving bitmap from " + url + e.toString());
        } finally {
            if (client != null) {
                //client.close();
            }
        }
        return null;
    }
}

Example of use:

downloader = new ImageDownloader();
ImageView image_profile =(ImageView) row.findViewById(R.id.image_profile);
downloader.download(url, image_profile);