ViewHolder模式的简洁写法
大家通常怎么写ViewHolder呢?
ViewHolder holder = null; if(convertView == null){ convertView = mInflater.inflate(R.layout.xxx null); holder = new ViewHolder(); holder.tvXXX = (TextView)findViewById(R.id.xxx); //...一连串的findViewById } else{ holder = (ViewHolder) convertView.getTag(); } private static class ViewHolder{ TextView tvXXX; //很多view的定义 }
这么写一次还行,但问题是总有很多很多的ViewAdapter要这么写,每次都repeat,repeat,repeat 累啊。 所以,有这么一种简洁的写法分享给大家,先声明,从国外网站上看的,不是自己原创的,但确实很喜欢这个简洁的设计。
ViewHolder这么写(只提供一个静态方法,其实可以加一个私有构造函数防止外部实例化),代码很简单,看过就明白了
public class ViewHolder { // I added a generic return type to reduce the casting noise in client code @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; } }
在getView里这样
@Override public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { convertView = LayoutInflater.from(context) .inflate(R.layout.banana_phone, parent, false); } ImageView bananaView = ViewHolder.get(convertView, R.id.banana); TextView phoneView = ViewHolder.get(convertView, R.id.phone); BananaPhone bananaPhone = getItem(position); phoneView.setText(bananaPhone.getPhone()); bananaView.setImageResource(bananaPhone.getBanana()); return convertView; }
哈哈,完成了,果断把这个ViewHolder类加入自己的utils,一劳永逸了以后~
值得注意的是SparseArray这个知识点,优化过的存储integer和object键值对的hashmap,网上资料很多这里就不废话了~