Android ListView中的ViewHolder的優化(逛部落格時看到的優化)

    在看各個網站看部落格文章的時候，看到了好多優化ViewHolder的文章。雖然，其中增加了判斷，但是減少了ViewHolder的臃腫寫法。他們是如何優化的呢？如下：

優化一:  

public static <T extends View> T getHolderView(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;
	}
           

優化二：

public static <T extends View> T getHolderView(View view, int id) {
		SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();
		View childView;
		if (viewHolder == null) {
			viewHolder = new SparseArray<View>();
			view.setTag(viewHolder);
			// 先建立的ViewHolder自然沒有緩存View是以不用判斷
			childView = view.findViewById(id);
			viewHolder.put(id, childView);
		} else {
			childView = viewHolder.get(id);
			if (childView == null) {
				childView = view.findViewById(id);
				viewHolder.put(id, childView);
			}
		}
		return (T) childView;
	}