android ListView使用优化--缓存机制

ListView缓存机制

@Override

public View getView(int position, View convertView, ViewGroup parent) {

         ViewHolder holder;

         if (convertView == null) {

                   convertView = inflater.inflate(R.layout.type_item, null);

                   holder = new ViewHolder();

                   holder.imageView = (ImageView)convertView.findViewById(R.id.app_icon);

                   holder.textView = (TextView)convertView.findViewById(R.id.app_name);

                   convertView.setTag(holder);

         } else {

                   holder = (ViewHolder)convertView.getTag();

         }

         holder.imageView.setImageResource(R.drawable.index_default_image);

         holder.textView.setText("");

         return convertView;

}

 

/**

 * ViewHolder

 */

static class ViewHolder {

 

         ImageView imageView;

         TextView  textView;

}

通过convertView是否为null减少layout inflate次数，通过静态的ViewHolder减少findViewById的次数，这两个函数尤其是inflate是相当费时间的。