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About optimizing the implementation of the ViewHolder template in ListView

Thus, the well-known ViewHolder template usually looks like (ListAdapter):

    ...

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

        final Album album = albums.get(position);

        ViewHolder viewHolder = null;
        if (convertView==null){
            convertView = inflater.inflate(R.layout.albums_list_item, null);

            final ImageView albumImage = (ImageView) convertView.findViewById(R.id.album_icon);

            final TextView txtTitle = (TextView) convertView.findViewById(R.id.album_title);

            final TextView txtDescription = (TextView) convertView.findViewById(R.id.album_copyright);

            viewHolder = new ViewHolder();
            viewHolder.albumImage = albumImage;
            viewHolder.txtTitle = txtTitle;
            viewHolder.txtDescription = txtDescription;
            convertView.setTag(viewHolder);
        }
        else
            viewHolder = (ViewHolder)convertView.getTag();

        viewHolder.txtTitle.setText(album.getTitle(locale));
        viewHolder.txtDescription.setText(album.getCopyrightInfo(locale));
        ...
        return convertView;
    }

while the ViewHolder class usually looks like this:

static class ViewHolder{
    public ImageView previewImage;
    public TextView txtTitle;
    public TextView txtDescription;
}

My questions are about the implementation of ViewHolder.
1) Why doesn't he use a constructor instead of initializing each individual field?
2) Why does it use the default access type instead of secure (in fact, it should be closed, but this affects performance due to the static accessories created by by JIT)? Well, I think it's only about inheritance.
So why the following pattern is not better (excluding the "protected vs default" access type):

protected static class ViewHolder{
    public final ImageView previewImage;
    public final TextView txtTitle;
    public final TextView txtDescription;

    public ViewHolder (final ImageView previewImage,  final TextView txtTitle, final TextView txtDescription){
        this.previewImage = previewImage;
        this.txtTitle = txtTitle;
        this.txtDescription = txtDescription;
    }
}

and the only change in the ListAdapter:

...
final TextView txtDescription = (TextView) convertView.findViewById(R.id.album_copyright);
viewHolder = new ViewHolder(albumImage, txtTitle, txtDescription);
convertView.setTag(viewHolder);
...

. ? - ?

+5
3

, . , . , - .

+2

, , , ViewHolder . , ,

    private class ViewHolder
    {
      protected final ImageView image;
      protected final TextView  title;
      protected final TextView  status;

      public ViewHolder( final View root )
      {
         image = (ImageView) root.findViewById( R.id.artist_image );
         title = (TextView) root.findViewById( R.id.artist_title );
         status = (TextView) root.findViewById( R.id.artist_status );
      }
   }

getView(...)

 View row = convertView;

  if ( null == row || null == row.getTag() )
  {
     row = inflater.inflate( R.layout.adapter_artists, null );
     holder = new ViewHolder( row );
     row.setTag( holder );
  }
  else
  {
     holder = (ViewHolder) row.getTag();
  }

, getView(...) . , , , , , .

+5

In my opinion, this is the best way to do this, but there is something that I would change with my code. You have a constructor in ViewHolderwhere you set the views, but as I see it, you are not using it in your code. I would use it or just delete it. And one more thing, there is actually a better way to get the same effect, but it will only work on Android 4+:

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

    ImageView mIcon;
    TextView mName;
    if (convertView == null) {
        convertView = LayoutInflater.from(context)
          .inflate(R.layout.my_contact_listing, parent, false);
        mIcon = (ImageView) convertView.findViewById(R.id.contact_icon);
        mName = (TextView) convertView.findViewById(R.id.contact_name);
        convertView.setTag(R.id.contact_icon, mIcon);
        convertView.setTag(R.id.contact_name, mName);
    } else {
        mIcon = (ImageView) convertView.getTag(R.id.contact_icon);
        mName = (TextView) convertView.getTag(R.id.contact_name);
    }

    Contact mContact = getItem(position);
    mName.setText(mContact.getName());
    mIcon.setImageResource(mContact.getIcon());

    return convertView;
}
+1
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