ListView的简单优化

public class Myadapter extends BaseAdapter {
    List<String> date;
    Context context;

    //构造方法
    public Myadapter(List<String> date, Context context) {
        this.date = date;
        this.context = context;
    }

    //获取ListView的总条目数
    @Override
    public int getCount() {
        return date.size();
    }

    //条目的索引
    @Override
    public Object getItem(int position) {
        return date.get(position);
    }

    //获取条目的位置
    @Override
    public long getItemId(int position) {
        return position;
    }

    /*
     * 渲染（填充），调用data.size次
     * position 索引
     * convertView 条目的View
     * parent ：Listview
     * */
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        //当convertView首次加载的时候
        if (convertView == null) {
            //获取打气筒
            LayoutInflater inflater = LayoutInflater.from(context);
            //填充单个Item
            convertView = inflater.inflate(R.layout.item_main, null);
            //获取Viewholder对象，减少findViewById的次数
            holder = new ViewHolder();
            //从填充的条目View中找到我们所关心的控件
            holder.textView = convertView.findViewById(R.id.tv_my);
            //将holder装进convertView的口袋
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        //填充数据
        holder.textView.setText(date.get(position));
        return convertView;
    }
    //创建一个容器装要复用的View
    static class ViewHolder {
        TextView textView;
    }
}