Image Loader : Image « 2D Graphics « Android

1. Android
2. 2D Graphics
3. Image

Image Loader

   
//package com.discogs.cupcake.utils;
 
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.widget.ImageView;
 
public class ImageLoader 
{
  static private ImageLoader _instance;
  static public ImageLoader getInstance() 
  {
    if (_instance == null) 
    {
      _instance = new ImageLoader();
    }
    return _instance;
  }
 
  private HashMap<String , Bitmap> _urlToBitmap;
  private Queue<Group> _queue;
  private DownloadThread _thread;
  private Bitmap _missing;
  private boolean _busy;
 
    /**
     * Constructor
     */
  private ImageLoader () 
  {
    _urlToBitmap = new HashMap<String , Bitmap>();
    _queue = new LinkedList<Group>();
    _busy = false;
  }
 
  public Bitmap get(String url) 
  {
    return _urlToBitmap.get(url);
  }
 
  public void load(ImageView image, String url) 
  {
    load(image, url, false);
  }
 
  public void load(ImageView image, String url, boolean cache) 
  {
    if (_urlToBitmap.get(url) != null) 
    {
      if (image!=null) 
      {
        image.setImageBitmap(_urlToBitmap.get(url));
      }
    } 
    else 
    {
      image.setImageBitmap(null);
      queue(image, url, cache);
    }
  }
 
  public void queue(ImageView image, String url, boolean cache) 
  {
    Iterator<Group> it = _queue.iterator();
  
    if (image!=null) 
    {
      while (it.hasNext()) 
      {
        if (it.next().image.equals(image)) 
        {
          it.remove();
          break;
        }
      }
    } 
    else if (url!=null) 
    {
      while (it.hasNext()) 
      {
        if (it.next().url.equals(url)) 
        {
          it.remove();
          break;
        }
      }
    }
    
    _queue.add(new Group(image, url, null, cache));
    loadNext();
  }
 
  public void clearQueue() 
  {
    _queue = new LinkedList<Group>();
  }
 
  public void clearCache() 
  {
    _urlToBitmap = new HashMap<String , Bitmap>();
  }
 
  public void cancel() 
  {
    clearQueue();
  
    if ( _thread != null ) 
    {
      _thread.disconnect();
      _thread = null;
    }
  }
 
  public void setMissingBitmap(Bitmap bitmap) 
  {
    _missing = bitmap;
  }
 
  private void loadNext() 
  {
    Iterator<Group> it = _queue.iterator();
    
    if (!_busy && it.hasNext()) 
    {
      _busy = true;
      Group group = it.next();
      it.remove();
      
      // double check image availability
      if (_urlToBitmap.get(group.url) != null) 
      {
        if (group.image!=null) 
        {
          group.image.setImageBitmap(_urlToBitmap.get(group.url));
        }
        
        _busy = false;
        loadNext();
      } 
      else 
      {
        _thread = new DownloadThread(group);
        _thread.start();
      }
    }
  }
 
  private void onLoad() 
  {
    if (_thread != null) 
    {
      Group group = _thread.group;
    
      if (group.bitmap != null) 
      {
        if (group.cache) 
        {
          _urlToBitmap.put(group.url, group.bitmap);
        }
        
        if (group.image != null) 
        {
          group.image.setImageBitmap(group.bitmap);
        }
      } 
      else if (_missing != null) 
      {
        if (group.image != null) 
        {
          group.image.setImageBitmap(_missing);
        }
      }
    }
    
    _thread = null;
    _busy = false;
    loadNext();
  }
 
  private class Group 
  {
    public Group(ImageView image, String url, Bitmap bitmap, boolean cache) 
    {
      this.image = image;
      this.url = url;
      this.bitmap = bitmap;
      this.cache = cache;
    }
    public ImageView image;
    public String url;
    public Bitmap bitmap;
    public boolean cache;
  }
 
  private class DownloadThread extends Thread 
  {
    final Handler threadHandler = new Handler();
      final Runnable threadCallback = new Runnable() 
      {
          public void run() 
          {
            onLoad();
          }
      };
    private HttpURLConnection _conn;
    public Group group;
    public DownloadThread(Group group) 
    {
      this.group = group;
    }
 
    @Override
    public void run() 
    {
      InputStream inStream = null;
      _conn = null;
    
      try 
      {
        _conn = (HttpURLConnection) new URL(group.url).openConnection();
        _conn.setDoInput(true);
        _conn.connect();
        inStream = _conn.getInputStream();
        group.bitmap = BitmapFactory.decodeStream(inStream);
        inStream.close();
        _conn.disconnect();
        inStream = null;
        _conn = null;
      }
      catch (Exception ex) 
      {
        // nothing
      }
      
      if (inStream != null) 
      {
        try 
        {
          inStream.close();
        } 
        catch (Exception ex) 
        {
        }
      }
      disconnect();
      inStream = null;
      _conn = null;
      threadHandler.post(threadCallback);
    }
 
    public void disconnect() 
    {
      if (_conn != null) 
      {
        _conn.disconnect();
      }
    }
  }
}

   
    
    
  

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