在 getView() 方法中,每次都将布局重新加载了一遍,当 ListView 快速滚动的时候,这就会成为性能的瓶颈.
getView() 方法中还有一个 convertView 参数,这个参数用于将之前加载好的布局进行缓存,以便之后可以进行重用.
因此我们可以通过他来进行优化:
不过,目前我们的这份代码还是可以继续优化的,虽然现在已经不会再重复去加载布局,但是每次在 getView() 方法中还是会调用 View 的 findViewById() 方法来获取一次控件的实例.我们可以借助一个 ViewHolder 来对这部分性能进行优化:
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Fruit fruit = getItem(position);
View view;
if (convertView == null) {
view = LayoutInflater.from(getContext()).inflate(resourceId, parent,
false);
} else {
view = convertView;
}
ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);
fruitImage.setImageResource(fruit.getImageId());
fruitName.setText(fruit.getName());
return view;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Fruit fruit = getItem(position);
View view;
ViewHolder viewHolder;
if (convertView == null) {
view = LayoutInflater.from(getContext()).inflate(resourceId, parent,
false);
viewHolder = new ViewHolder();
viewHolder.fruitImage = (ImageView) view.findViewById
(R.id.fruit_image);
viewHolder.fruitName = (TextView) view.findViewById (R.id.fruit_name);
view.setTag(viewHolder); // 将ViewHolder存储在View中
} else {
view = convertView;
viewHolder = (ViewHolder) view.getTag(); // 重新获取ViewHolder
}
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName.setText(fruit.getName());
return view;
}
class ViewHolder {
ImageView fruitImage;
TextView fruitName;
}
来源: http://www.bubuko.com/infodetail-2461745.html