GridView Performance lag with Custom CursorAdapters

Question

I'm currently trying to get the hang of android developemnt and so far its been going good(Well until now). I am currently playing around with Custom Cursor adapters for my grid view. I read using a cursor adapter takes the load of the main UI thread which sounds efficient, so i tried to implement my own cursor adapter as follows

public class VideoListAdapter extends SimpleCursorAdapter{

private Context ctx;
private int parent_layout_id;

ArrayList<VideoModel> videoList = new ArrayList<VideoModel>();

public VideoListAdapter(
        Context ctx,
        int parent_layout_id,
        Cursor c,
        String[] fromColumns,
        int[] toView)
{
    super(ctx,parent_layout_id,c,fromColumns,toView);
    this.ctx = ctx;
    this.parent_layout_id = parent_layout_id;
}

@Override
public void bindView(View v, Context context, Cursor c) {

    //gets title column
    int titleColumn = c.getColumnIndex(MediaStore.Video.Media.TITLE);
    String title = c.getString(titleColumn);
    TextView titleView =(TextView) v.findViewById(R.id.video_title);
    titleView.setText(title);

    //gets duration
    int durationColumn = c.getColumnIndex(MediaStore.Video.Media.DURATION);
    String duration = c.getString(durationColumn);
    TextView durationView = (TextView) v.findViewById(R.id.video_date);
    durationView.setText(duration);

    //gets Thumb
    int videoDataColumn = c.getColumnIndex(MediaStore.Video.Media.DATA);
    String videodataUrl = c.getString(videoDataColumn);
    MediaMetadataRetriever mmr = new MediaMetadataRetriever();
    mmr.setDataSource(videodataUrl);
    Bitmap bm = mmr.getFrameAtTime(1000);
    ImageView imgv = (ImageView) v.findViewById(R.id.video_thumb);
    imgv.setScaleType(ImageView.ScaleType.CENTER_CROP);
    imgv.setImageBitmap(bm);
}

@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
    Cursor c = getCursor();

    //get layout inflater
    final LayoutInflater li=LayoutInflater.from(context);
    View v = li.inflate(parent_layout_id,parent,false);

    //gets title column
    int titleColumn = c.getColumnIndex(MediaStore.Video.Media.TITLE);
    String title = c.getString(titleColumn);
    TextView titleView =(TextView) v.findViewById(R.id.video_title);
    titleView.setText(title);

    //gets duration
    int durationColumn = c.getColumnIndex(MediaStore.Video.Media.DURATION);
    String duration = c.getString(durationColumn);
    TextView durationView = (TextView) v.findViewById(R.id.video_date);
    durationView.setText(duration);

    //gets Thumb
    int videoDataColumn = c.getColumnIndex(MediaStore.Video.Media.DATA);
    String videodataUrl = c.getString(videoDataColumn);
    MediaMetadataRetriever mmr = new MediaMetadataRetriever();
    mmr.setDataSource(videodataUrl);
    Bitmap bm = mmr.getFrameAtTime(1000);
    ImageView imgv = (ImageView) v.findViewById(R.id.video_thumb);
    imgv.setScaleType(ImageView.ScaleType.CENTER_CROP);
    imgv.setImageBitmap(bm);
    return v;
}

@Override
public Cursor runQueryOnBackgroundThread(CharSequence constraint) {
    return super.runQueryOnBackgroundThread(constraint);
}

}

What i'm trying to achieve is to fetch list of video files from the external media storage and display them in a gridview. the standard thumbnails are abit too small for the style of layout i have in mind so i used the MediaMetadataRetriever to fetch frames from each of the video files and used that as thumbnails. Like so

When i ran the application the scroll performance of my gridView worsened. What am I missing. i know the SimpleCursorAdapter class has an overridable method runQueryOnBackgroundThread but i dont even know what to put in there or how to use it. Any pointers will be very much appreciated and forgive my smudge face ;)

Answer 1

First of all bind your Gridview using ViewHolder and second one is save your thumb(bitmap) in existing arrayList so you can not do have to same process while scrolling.