Video thumbnail arrayadopter is slow on scroll

Question

I have created an adopter to display images thumbnail of video form the specific folder but when I scroll it lags a little but why is that? Below is the code: Main activity class ``` public class TestvideolistingActivity extends ListActivity { String filename = null; String filePath = null; String dirNameSlash = "/videotest/"; String dirName = "videotest"; String path = Environment.getExternalStorageDirectory() + dirNameSlash ; String[] values; String deleteFile ; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // getting the own adapter getInit(); } @Override protected void onResume() { getInit(); super.onResume(); } public void getInit() { deleteFile = null; values = getFilesArrayFromSdCard(); setListAdapter(new MyAdapter(this, values)); } protected void onListItemClick(ListView l, View v, int position, long id) { String item = (String) getListAdapter().getItem(position); Intent intentToPlayVideo = new Intent(Intent.ACTION_VIEW); inten…

Accepted Answer

The listview is lagging because you are creating new Thumbnails in getView() every time. There is just no caching or re-use. As the use scrolls up/down , getView() is called and time consuming process of creating thumbnails happen, hence the lag. You will also run `Out of Memory` soon.

Create and keep an Array of Bitmaps, with the same length as the number of elements in the datasource and store your thumbnails in the array. Take out the bitmap from the array for that particular position inside `getView()`. This should considerably increase the performance.

EDIT I have added a Hasmap of bitmaps to demonstrate the re-use.

```
 public MyAdapter(Activity context, String[] names) {
    super(context, R.layout.rowlayout, names);
    this.context = context;
    this.names = names;
    filePath = Environment.getExternalStorageDirectory() + dirNameSlash;
    formatter = new SimpleDateFormat(dateFormat);
cacheBitmap = new HashMap<String, Bitmap>(names.length);
initCacheBitmap();
}

private void initCacheBitmap() {
    for(String string:names)
        cacheBitmap.put(string, ThumbnailUtils.createVideoThumbnail(filePath+string, Thumbnails.MICRO_KIND));

}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

View rowView = convertView;
    if (rowView == null) {
        LayoutInflater inflater = context.getLayoutInflater();
        rowView = inflater.inflate(R.layout.rowlayout, null);
        ViewHolder viewHolder = new ViewHolder();
        viewHolder.text = (TextView) rowView.findViewById(R.id.label);
        viewHolder.image = (ImageView) rowView.findViewById(R.id.icon);
        rowView.setTag(viewHolder);
    }

ViewHolder holder = (ViewHolder) rowView.getTag();
    // Video file name
    String s = names[position];

holder.text.setText(s);

holder.image.setImageBitmap(cacheBitmap.get(s));

return rowView;
}}
```

Video thumbnail arrayadopter is slow on scroll

Solution

Problem