Adapting ListView adapter with an ImageLoader Class in Android

I have a custom ListView adapter which implements an ImageThreadLoader class. Unfortunately, the class doesn't enable a cache option-download the images from the web and save them as cache.

And then I found this LazyList project really useful, it behaves quite the same like my ImageThreadLoader class but it's able to save the images as cache. So, I want to implement its ImageLoader class to my current custom ListView adapter.

Unfortunately the structure of my codes and the Lazylist's is quite different, resulting some conflicts on my attempts. For example, the LazyList use array of strings for the image URL, in the other hand I use JSON as the source of image URL.

That's why I need help to adapt my ListView adapter to this ImageLoader class.

Here are the codes:

ImageLoader Class which I want implement to my custom ListView adapter:

public class ImageLoader {

    //the simplest in-memory cache implementation. This should be replaced with something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
    private HashMap<String, Bitmap> cache=new HashMap<String, Bitmap>();

    private File cacheDir;

    public ImageLoader(Context context){
        //Make the background thead low priority. This way it will not affect the UI performance
        photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);

        //Find the dir to save cached images
        if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
            cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"Android/data/LazyList");
        else
            cacheDir=context.getCacheDir();
        if(!cacheDir.exists())
            cacheDir.mkdirs();
    }

    final int stub_id=R.drawable.stub;
    public void DisplayImage(String url, Activity activity, ImageView imageView)
    {
        if(cache.containsKey(url))
            imageView.setImageBitmap(cache.get(url));
        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) 
    {
        //I identify images by hashcode. Not a perfect solution, good for the demo.
        String filename=String.valueOf(url.hashCode());
        File f=new File(cacheDir, filename);

        //from SD cache
        Bitmap b = decodeFile(f);
        if(b!=null)
            return b;

        //from web
        try {
            Bitmap bitmap=null;
            InputStream is=new URL(url).openStream();
            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){开发者_开发百科
                if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<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<PhotoToLoad> photosToLoad=new Stack<PhotoToLoad>();

        //removes all instances of this ImageView
        public void Clean(ImageView image)
        {
            for(int j=0 ;j<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);
                        cache.put(photoToLoad.url, bmp);
                        Object tag=photoToLoad.imageView.getTag();
                        if(tag!=null && ((String)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() {
        //clear memory cache
        cache.clear();

        //clear SD cache
        File[] files=cacheDir.listFiles();
        for(File f:files)
            f.delete();
    }

}

the custom list view adapter from the LazyList project:

public class LazyAdapter extends BaseAdapter {

    private Activity activity;
    private String[] data;
    private static LayoutInflater inflater=null;
    public ImageLoader imageLoader; 

    public LazyAdapter(Activity a, String[] d) {
        activity = a;
        data=d;
        inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        imageLoader=new ImageLoader(activity.getApplicationContext());
    }

    public int getCount() {
        return data.length;
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    public static class ViewHolder{
        public TextView text;
        public ImageView image;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        View vi=convertView;
        ViewHolder holder;
        if(convertView==null){
            vi = inflater.inflate(R.layout.item, null);
            holder=new ViewHolder();
            holder.text=(TextView)vi.findViewById(R.id.text);;
            holder.image=(ImageView)vi.findViewById(R.id.image);
            vi.setTag(holder);
        }
        else
            holder=(ViewHolder)vi.getTag();

        holder.text.setText("item "+position);
        holder.image.setTag(data[position]);
        imageLoader.DisplayImage(data[position], activity, holder.image);
        return vi;
    }
}

and here's my custom ListView adapter: ProjectAdapter class

public class ProjectAdapter extends ArrayAdapter<Project> {

    int resource;
    String response;
    Context context;
    private final static String TAG = "MediaItemAdapter";

    private ImageThreadLoader imageLoader = new ImageThreadLoader();

    //Initialize adapter
    public ProjectAdapter(Context context, int resource, List<Project> items) {
        super(context, resource, items);
        this.resource=resource;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        TextView textTitle;
        final ImageView image;

        Project pro = getItem(position);

        LinearLayout projectView;
      //Inflate the view
        if(convertView==null)
        {
            projectView = new LinearLayout(getContext());
            String inflater = Context.LAYOUT_INFLATER_SERVICE;
            LayoutInflater vi;
            vi = (LayoutInflater)getContext().getSystemService(inflater);
            vi.inflate(resource, projectView, true);
        }
        else
        {
            projectView = (LinearLayout) convertView;
        }

        try {
          textTitle = (TextView)projectView.findViewById(R.id.txt_title);
          image = (ImageView)projectView.findViewById(R.id.image);
        } catch( ClassCastException e ) {
          Log.e(TAG, "Your layout must provide an image and a text view with ID's icon and text.", e);
          throw e;
        }


        Bitmap cachedImage = null;
        try {
          cachedImage = imageLoader.loadImage(pro.smallImageUrl, new ImageLoadedListener() {
          public void imageLoaded(Bitmap imageBitmap) {
          image.setImageBitmap(imageBitmap);
          notifyDataSetChanged();                }
          });
        } catch (MalformedURLException e) {
          Log.e(TAG, "Bad remote image URL: " + pro.smallImageUrl, e);
        }

        textTitle.setText(pro.project_title);

        if( cachedImage != null ) {
          image.setImageBitmap(cachedImage);
        }

        return projectView;
    }

}

I posted code in this Code for Image Loader..

Check that code ..

1.In your Activity get all the images URL in String Array and pass it..

dealAdapter = new LazyAdapter(Activityname.this,VALUE_image);

where VALUE_image contains your images.

Important thing is that check whether you add permission in Manifest file

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

Create a file namelyImageLoader.class and paste the code of Image Loader given in that link

Then create file namely Utils.class and paste code of Utils in that link.

In the above code it checks whether Sdcard is present if so the create folder in Sdcard and store all images in compressed format and retrive it later..

Else if no it store images in Cache memory..

First time its load image from the server and next time it check whether it is in Sdcard or in Cache Memory if so retrive the image and Displays..

Check it..