viewholder 封裝

萬能的viewholder,省去創建viewholder的步驟

public class BaseViewHolder {
	    @SuppressWarnings("unchecked")
	    public static <T extends View> T get(View view, int id) {
	        SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();
	        if (viewHolder == null) {
	            viewHolder = new SparseArray<View>();
	            view.setTag(viewHolder);
	        }
	        View childView = viewHolder.get(id);
	        if (childView == null) {
	            childView = view.findViewById(id);
	            viewHolder.put(id, childView);
	        }
	        return (T) childView;
	    }

}