android:ViewHolder模式

2023-02-13 08:32:52

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;
}