How do I implement view recycling mechanism for PagerAdapter?

Question

I have a pager adapter that suppose to inflate a complex view representing a calendar.

It takes around ~350 ms to inflate each year of the calendar.

To improve performance I would like to implement the same mechanism that exists in the ListView array adapter of recycling views (convertView parameter in getView()).

Here is my current getView() from the adapter.

@Override protected View getView(VerticalViewPager pager, final DateTileGrid currentDataItem, int position) {     mInflater = LayoutInflater.from(pager.getContext());          // This is were i would like to understand weather is should use a recycled view or create a new one.     View datesGridView = mInflater.inflate(R.layout.fragment_dates_grid_page, pager, false);       DateTileGridView datesGrid = (DateTileGridView) datesGridView.findViewById(R.id.datesGridMainGrid);     TextView yearTitle = (TextView) datesGridView.findViewById(R.id.datesGridYearTextView);     yearTitle.setText(currentDataItem.getCurrentYear() + "");     DateTileView[] tiles = datesGrid.getTiles();      for (int i = 0; i < 12; i++)     {         String pictureCount = currentDataItem.getTile(i).getPictureCount().toString();         tiles[i].setCenterLabel(pictureCount);         final int finalI = i;         tiles[i].setOnCheckedChangeListener(new DateTileView.OnCheckedChangeListener() {             @Override             public void onCheckedChanged(DateTileView tileChecked, boolean isChecked)             {                 DateTile tile = currentDataItem.getTile(finalI);                 tile.isSelected(isChecked);             }         });     }      return datesGridView; } 

Any pointers or direction for implementing such a behavior? In particular how can I know in the adapter that one of the DateTileGridViews is being swiped of the screen so I could save it in memory to reuse it next time.

Answer 1

So I have figured it out.

1. overwrite destroyItem(ViewGroup container, int position, Object view) ans save you cached view
2. create a separate method to see if there is any chance to use a recycled view or should you inflate a new one.
3. remember to remove the recycled view from cache once its been used to avoid having same view attaching same view to the pager.

here is the code.. I used a Stack of view to cache all removed views from my pager

private View inflateOrRecycleView(Context context) {      View viewToReturn;     mInflater = LayoutInflater.from(context);     if (mRecycledViewsList.isEmpty())     {         viewToReturn = mInflater.inflate(R.layout.fragment_dates_grid_page, null, false);     }     else     {         viewToReturn = mRecycledViewsList.pop();         Log.i(TAG,"Restored recycled view from cache "+ viewToReturn.hashCode());     }       return viewToReturn; }  @Override public void destroyItem(ViewGroup container, int position, Object view) {     VerticalViewPager pager = (VerticalViewPager) container;     View recycledView = (View) view;     pager.removeView(recycledView);     mRecycledViewsList.push(recycledView);     Log.i(TAG,"Stored view in cache "+ recycledView.hashCode()); } 

do not forget to instantiate the stack in the adapter constructor.