GridView scrolling problem on Android

Question

this must be somethng very simple I\'m overlooking, but I have the following problem (the post is rather lengthy, but I want to provide as much info as possible :) ).

I

Answer 1

The answer is view recycling.

In general your getView should always be something of the form:

public class ImageAdapter extends BaseAdapter {

    private List mUrls; // put your urls here
    private Map mImages; // cache your images here

    public ImageAdapter() {
        ...
        mUrls = new ArrayList();
        mImages = new HashMap();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder; // Use the ViewHolder pattern for efficiency

        if (convertView == null) {
            // first time this view has been created so inflate our layout
            convertView = View.inflate(this, R.layout.my_grid_item, null);
            holder = new ViewHolder();
            holder.image = convertView.findViewById(R.id.image);
            holder.text = convertView.findViewById(R.id.text);
            convertView.setTag(holder); // set the View holder
        } else {
           holder = (ViewHolder) convertView.getTag();
        }

        // update the current view - this must be done EVERY
        // time getView is called due to view recycling
        holder.text.setText(Integer.toString(position));

        // check our cache for the downloaded image
        final String url = mUrls.get(position);
        if (mImages.get(url) != null)
            holder.image.setImageDrawable(mImages.get(url));
        else
            loadImage(url, holder.image);

        // return our view
        return convertView;
    }

    public loadImage(final String url, final ImageView image) {
        // load an image (maybe do this using an AsyncTask
        // if you're loading from network
    }

    ...
}

Where your ViewHolder class would look something like

public class ViewHolder {
    ImageView thumbImage;
    TextView text;
}

Then you shouldn't run into any problems. Also I'm not sure why you needed to sleep in your getView? That will slow down scrolling of your GridView.