listview加载显示图片

public class ImageAndTextListAdapter extends ArrayAdapter<ImageAndText> {

	    private ListView listView;
	    private AsyncImageLoader asyncImageLoader;

	    public ImageAndTextListAdapter(Activity activity, List<ImageAndText> imageAndTexts, ListView listView) {
	        super(activity, 0, imageAndTexts);
	        this.listView = listView;
	        asyncImageLoader = new AsyncImageLoader();
	    }

	    public View getView(int position, View convertView, ViewGroup parent) {
	        Activity activity = (Activity) getContext();

	        // Inflate the views from XML
	        View rowView = convertView;
	        ViewCache viewCache;
	        if (rowView == null) {
	            LayoutInflater inflater = activity.getLayoutInflater();
	            rowView = inflater.inflate(R.layout.image_and_text_row, null);
	            viewCache = new ViewCache(rowView);
	            rowView.setTag(viewCache);
	        } else {
	            viewCache = (ViewCache) rowView.getTag();
	        }
	        ImageAndText imageAndText = getItem(position);

	        // Load the image and set it on the ImageView
	        String imageUrl = imageAndText.getImageUrl();
	        ImageView imageView = viewCache.getImageView();
	        imageView.setTag(imageUrl);
	        Drawable cachedImage = asyncImageLoader.loadDrawable(imageUrl, new ImageCallback() {
	            public void imageLoaded(Drawable imageDrawable, String imageUrl) {
	                ImageView imageViewByTag = (ImageView) listView.findViewWithTag(imageUrl);
	                if (imageViewByTag != null) {
	                    imageViewByTag.setImageDrawable(imageDrawable);
	                }
	            }
	        });
			if (cachedImage == null) {
				imageView.setImageResource(R.drawable.default_image);
			}else{
				imageView.setImageDrawable(cachedImage);
			}
	        // Set the text on the TextView
	        TextView textView = viewCache.getTextView();
	        textView.setText(imageAndText.getText());

	        return rowView;
	    }

}
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public class AsyncImageLoader {

     private HashMap<String, SoftReference<Drawable>> imageCache;
      
         public AsyncImageLoader() {
             imageCache = new HashMap<String, SoftReference<Drawable>>();
         }
      
         public Drawable loadDrawable(final String imageUrl, final ImageCallback imageCallback) {
             if (imageCache.containsKey(imageUrl)) {
                 SoftReference<Drawable> softReference = imageCache.get(imageUrl);
                 Drawable drawable = softReference.get();
                 if (drawable != null) {
                     return drawable;
                 }
             }
             final Handler handler = new Handler() {
                 public void handleMessage(Message message) {
                     imageCallback.imageLoaded((Drawable) message.obj, imageUrl);
                 }
             };
             new Thread() {
                 @Override
                 public void run() {
                     Drawable drawable = loadImageFromUrl(imageUrl);
                     imageCache.put(imageUrl, new SoftReference<Drawable>(drawable));
                     Message message = handler.obtainMessage(0, drawable);
                     handler.sendMessage(message);
                 }
             }.start();
             return null;
         }
      
        public static Drawable loadImageFromUrl(String url) {
            URL m;
            InputStream i = null;
            try {
                m = new URL(url);
                i = (InputStream) m.getContent();
            } catch (MalformedURLException e1) {
                e1.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            Drawable d = Drawable.createFromStream(i, "src");
            return d;
        }
      
         public interface ImageCallback {
             public void imageLoaded(Drawable imageDrawable, String imageUrl);
         }

}