Hi! Today I'm going to tell you how to load data in
ListView items asynchronous in Android.
First. For example we'll build a list of images, that we download from the Internet.
Second. ListView item is the simple
LinearLayout with
ImageView.
Third. Our adapter code:
public class ImageListAdapter extends BaseAdapter {
private List itemsUrls;
private Context ctx;
public FeedListAdapter(Context ctx) {
this.ctx = ctx;
}
private class ViewHolder {
public ImageView image;
}
@Override
public int getCount() {
return itemsUrls.size();
}
@Override
public Status getItem(int pos) {
return itemsUrls.get(pos);
}
@Override
public long getItemId(int pos) {
return pos;
}
@Override
public View getView(int pos, View convertView, ViewGroup parent) {
View v = convertView;
if(v == null){
LayoutInflater vi = (LayoutInflater) ctx.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.status_item, null);
ViewHolder holder = new ViewHolder();
holder.image = (ImageView) v.findViewById(R.id.image);
v.setTag(holder);
}
ViewHolder holder = (ViewHolder)v.getTag();
//Setting the image url as a tag for the image view
holder.image.setTag(items.get(pos));
holder.image.setImageDrawable(null);
//starting async task for image loading
new ImageTask().execute(holder);
return v;
}
private class ImageTask extends AsyncTask {
private ImageView avatarImage;
private Bitmap av = null;
private String url;
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
if(result && av != null) {
if(avatarImage.getTag().toString().equals(url)) {
avatarImage.setImageBitmap(av);
}
}
}
@Override
protected Boolean doInBackground(ViewHolder... params) {
ViewHolder item = (ViewHolder) params[0];
boolean result = false;
if(item != null) {
try {
avatarImage = item.image;
url = item.image.getTag().toString();
av = getBitmapMethod(url);
result = true;
} catch (Exception e) {
e.printStackTrace();
}
}
return result;
}
}
}
Here it is, now we have the async image loading as in different twitter clients.
