大家通常怎麼寫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);
//...一連串的findViewById
}
else{
holder = (ViewHolder) convertView.getTag();
}
private static class ViewHolder{
TextView tvXXX;
//很多view的定義
}
這麼寫一次還行,但問題是總有很多很多的ViewAdapter要這麼寫,每次都repeat,repeat,repeat 累啊。
所以,有這麼一種簡潔的寫法分享給大家,先聲明,從國外網站上看的,不是自己原創的,但確實很喜歡這個簡潔的設計。ViewHolder這麼寫(只提供一個靜態方法,其實可以加一個私有構造函數防止外部實例化),代碼很簡單,看過就明白了
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;
}
}
@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,果斷把這個ViewHolder類加入自己的utils,一勞永逸了以後~
值得注意的是SparseArray這個知識點,優化過的存儲integer和object鍵值對的hashmap,網上資料很多這裏就不廢話了~