ListView优化注意点

ListView的优化:

1.复用convertView,使用listview中RecycleBin机制.

/**
         * Views that were on screen at the start of layout. This array is populated at the start of
         * layout, and at the end of layout all view in mActiveViews are moved to mScrapViews.
         * Views in mActiveViews represent a contiguous range of Views, with position of the first
         * view store in mFirstActivePosition.
         */
        private View[] mActiveViews = new View[0];

        /**
         * Unsorted views that can be used by the adapter as a convert view.
         */
        private ArrayList<View>[] mScrapViews;

listview的许多view呈现在Ui上，这样的View对我们来说是可见的，可以称为OnScreen的view(也为ActionView)。
view被上滚移出屏幕，这样的view称为offScreenView（也称为ScrapView）。
然后ScrapView会被listview删除，而RecycleBin会将这部分保存。
当listview底部需要显示view时会从RecycleBin里面取出一个ScrapView,减少对象的创建。

2.使用viewHolder避免重复的调用findViewById查找id

3.快速滑动不适合做大量异步任务，在滑动停止后进行异步请求，避免频繁的网络请求。

4.分页加载数据，避免一次请求过多数据。

5.getView中每次显示item都会调用，所以应该避免在里面执行耗时操作，如果是图片可以做三级缓存。

推荐的优化处理方式:

public View getView(int position, View convertView, ViewGroup parent) {
   3:     Log.d("MyAdapter", "Position:" + position + "---"
   4:             + String.valueOf(System.currentTimeMillis()));
   5:     ViewHolder holder;
   6:     if (convertView == null) {
   7:         final LayoutInflater inflater = (LayoutInflater) mContext
   8:                 .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
   9:         convertView = inflater.inflate(R.layout.list_item_icon_text, null);
  10:         holder = new ViewHolder();
  11:         holder.icon = (ImageView) convertView.findViewById(R.id.icon);
  12:         holder.text = (TextView) convertView.findViewById(R.id.text);
  13:         convertView.setTag(holder);
  14:     } else {
  15:         holder = (ViewHolder) convertView.getTag();
  16:     }
  17:     holder.icon.setImageResource(R.drawable.icon);
  18:     holder.text.setText(mData[position]);
  19:     return convertView;
  20: }
  21:  
  22: static class ViewHolder {
  23:     ImageView icon;
  24:  
  25:     TextView text;

ListView的RecycleBin机制-结合源码分析