title: Why gridview in Gallery app of the system dose not use viewholder?
body: <p>As a junior Android app developer, I know when we use a <code>gridview</code> or <code>listview</code> we should use the ViewHolder to optimalize the performance. When I want to build a gridview with multi selection, I find the selected views are changed after scrolling the gridview, so I want to know how does the <a href="https://android.googlesource.com/platform/packages/apps/Gallery/+/android-m-preview-1/src/com/android/camera/GalleryPicker.java" rel="nofollow">system gallery</a> achieve this purpose. But from the <code>getView()</code> funtion in <code>GalleryPickerAdapter</code> I can see it does not use the ViewHolder, why the google engineer does not use ViewHolder?</p>
  
  <pre><code> public View getView(final int position, View convertView,
                      ViewGroup parent) {
      View v;
      if (convertView == null) {
          v = mInflater.inflate(R.layout.gallery_picker_item, null);
      } else {
          v = convertView;
      }
      TextView titleView = (TextView) v.findViewById(R.id.title);
      GalleryPickerItem iv =
              (GalleryPickerItem) v.findViewById(R.id.thumbnail);
      Item item = mItems.get(position);
      iv.setOverlay(item.getOverlay());
      if (item.mThumbBitmap != null) {
          iv.setImageBitmap(item.mThumbBitmap);
          String title = item.mName + " (" + item.mCount + ")";
          titleView.setText(title);
      } else {
          iv.setImageResource(android.R.color.transparent);
          titleView.setText(item.mName);
      }
      // An workaround due to a bug in TextView. If the length of text is
      // different from the previous in convertView, the layout would be
      // wrong.
      titleView.requestLayout();
      return v;
  }
  </code></pre>