ViewHolder 优化

 1   @Override
 2         public View getView(int position, View convertView, ViewGroup parent) {
 3             View view;
 4             Holder holder;
 5 
 6             if (convertView == null) {
 7                 view = View.inflate(MainActivity.this, R.layout.item, null);
 8                 holder = new Holder();
 9                 holder.img = (ImageView) view.findViewById(R.id.img);
10                 holder.button1 = (Button) view.findViewById(R.id.button1);
11                 holder.button2 = (Button) view.findViewById(R.id.button2);
12                 view.setTag(holder);
13             } else {
14                 view = convertView;
15                 holder = (Holder) view.getTag();
16             }
17 
18             return view;
19         }