ViewHolder类和OOM管理

Question

Does using the ViewHolder class may prevent leaks and large heap retains?

   class holder
    {
        WeakReference<ImageView> img;

    }

holder holdr = new holder();
holder.img = ...

displayImage(holder.img);

Should I just pass it as a parameter, Instead of declaring it as global?

Answer 1

The ViewHolder-Pattern got developed mainly due to performance-issues when you are using a ListAdapter that displays some View-elements with the same structure over and over for each list-item.

Your code might call findViewById() frequently during the scrolling of ListView, which can slow down performance. Even when the Adapter returns an inflated view for recycling, you still need to look up the elements and update them. A way around repeated use of findViewById() is to use the "view holder" design pattern.

You should also make your ViewHolder-class static

You can read more about it on Googles Dev Page .

I also recommend watching this Google IO video