WheelRecycle.java

package hong.specialEffects.wheel;

import java.util.LinkedList;
import java.util.List;

import android.view.View;
import android.widget.LinearLayout;

/**
 * Recycle stores wheel items to reuse. 
 */
public class WheelRecycle {
        // Cached items
        private List<View> items;
        
        // Cached empty items
        private List<View> emptyItems;
        
        // Wheel view
        private WheelView wheel;
        
        /**
         * Constructor
         * @param wheel the wheel view
         */
        public WheelRecycle(WheelView wheel) {
                this.wheel = wheel;
        }

        /**
         * Recycles items from specified layout.
         * There are saved only items not included to specified range.
         * All the cached items are removed from original layout.
         * 
         * @param layout the layout containing items to be cached
         * @param firstItem the number of first item in layout
         * @param range the range of current wheel items 
         * @return the new value of first item number
         */
        public int recycleItems(LinearLayout layout, int firstItem, ItemsRange range) {
                int index = firstItem;
                for (int i = 0; i < layout.getChildCount();) {
                        if (!range.contains(index)) {
                                recycleView(layout.getChildAt(i), index);
                                layout.removeViewAt(i);
                                if (i == 0) { // first item
                                        firstItem++;
                                }
                        } else {
                                i++; // go to next item
                        }
                        index++;
                }
                return firstItem;
        }
        
        /**
         * Gets item view
         * @return the cached view
         */
        public View getItem() {
                return getCachedView(items);
        }

        /**
         * Gets empty item view
         * @return the cached empty view
         */
        public View getEmptyItem() {
                return getCachedView(emptyItems);
        }
        
        /**
         * Clears all views 
         */
        public void clearAll() {
                if (items != null) {
                        items.clear();
                }
                if (emptyItems != null) {
                        emptyItems.clear();
                }
        }

        /**
         * Adds view to specified cache. Creates a cache list if it is null.
         * @param view the view to be cached
         * @param cache the cache list
         * @return the cache list
         */
        private List<View> addView(View view, List<View> cache) {
                if (cache == null) {
                        cache = new LinkedList<View>();
                }
                
                cache.add(view);
                return cache;
        }

        /**
         * Adds view to cache. Determines view type (item view or empty one) by index.
         * @param view the view to be cached
         * @param index the index of view
         */
        private void recycleView(View view, int index) {
                int count = wheel.getViewAdapter().getItemsCount();

                if ((index < 0 || index >= count) && !wheel.isCyclic()) {
                        // empty view
                        emptyItems = addView(view, emptyItems);
                } else {
                        while (index < 0) {
                                index = count + index;
                        }
                        index %= count;
                        items = addView(view, items);
                }
        }
        
        /**
         * Gets view from specified cache.
         * @param cache the cache
         * @return the first view from cache.
         */
        private View getCachedView(List<View> cache) {
                if (cache != null && cache.size() > 0) {
                        View view = cache.get(0);
                        cache.remove(0);
                        return view;
                }
                return null;
        }

}