Android Open Source - TinyRss Image Manager

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License

The source code is released under:

Copyright (c) 2012, Tiny Mission LLC All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met...

Java Source Code

package com.tinymission.rss;
/*  w w w . ja  v a 2 s . c  o m*/
import java.io.*;
import java.util.HashMap;

import org.apache.http.*;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.graphics.*;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.*;


/** Retrieves and stores images for the feed.
 *
 */
public class ImageManager {
  
  public static final String LOG_TAG = "ImageManager";
  
  private HashMap<String, Bitmap> _bitmapCache;
  private HashMap<Integer, DownloaderTask> _tasks;

  public ImageManager() {
    _bitmapCache = new HashMap<String, Bitmap>();
    _tasks = new HashMap<Integer, ImageManager.DownloaderTask>();
  }
  
  
  public void download(String url, ImageView imageView) {
    Log.v(LOG_TAG, "(" + imageView.hashCode() + ") Requested download: " + url);
    // cancel any existing downloads
    cancelDownloaderTask(imageView);
    
    // try the cache first
    if (tryLoadCachedBitmap(url, imageView))
      return;
    
    // download the image
    DownloaderTask task = new DownloaderTask(imageView);
    task.execute(url);
    _tasks.put(imageView.hashCode(), task);
  }
  

  private DownloaderTask getDownloaderTask(ImageView imageView) {
    return _tasks.get(imageView.hashCode());
  }
  
  
  private void cancelDownloaderTask(ImageView imageView) {
    if (_tasks.containsKey(imageView.hashCode())) {
      DownloaderTask task = _tasks.get(imageView.hashCode());
      Log.v(LOG_TAG, "(" + imageView.hashCode() + ") Cancelled download: " + task.url);
      task.cancel(true);
    }
  }
  
  private void removeDownloaderTask(ImageView imageView) {
    _tasks.remove(imageView.hashCode());
  }
  
  private Bitmap downloadBitmap(String url) {
    Log.v(LOG_TAG, "Began download: " + url);
        // AndroidHttpClient is not allowed to be used from the main thread
        final DefaultHttpClient 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(LOG_TAG, "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);
        }
        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;
        }
    }
  
  
  /** Tries to load a bitmap associated with the given url from the cache into the image view.
   * @param url the url of the image
   * @param imageView the ImageView to load the image into
   * @return true if the bitmap was found in the cache
   */
  public boolean tryLoadCachedBitmap(String url, ImageView imageView) {
    if (_bitmapCache.containsKey(url)) {
      imageView.setImageBitmap(_bitmapCache.get(url));
      Log.v(LOG_TAG, "(" + imageView.hashCode() + ") Loaded cached: " + url);
      return true;
    }
    return false;
  }

  /** Adds the given bitmap to the cache associated with the url.
   * @param url
   * @param bitmap
   */
  public void addBitmapToCache(String url, Bitmap bitmap) {
    _bitmapCache.put(url, bitmap);
  }
  
  /**
     * The actual AsyncTask that will asynchronously download the image.
     */
    class DownloaderTask extends AsyncTask<String, Void, Bitmap> {
        private String url;
        private final ImageView _imageView;

        public DownloaderTask(ImageView imageView) {
          _imageView = 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) {
            addBitmapToCache(url, bitmap);
            if (_imageView != null) {
                DownloaderTask bitmapDownloaderTask = getDownloaderTask(_imageView);
                // Change bitmap only if this process is still associated with it
                if (this == bitmapDownloaderTask) {
                  _imageView.setImageBitmap(bitmap);
                    removeDownloaderTask(_imageView);
              Log.v(LOG_TAG, "(" + _imageView.hashCode() + ") Completed download: " + url);
                }
            }
        }
    }
  
}

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