listview没显示内容出来

Question

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

//缓存目录
cache=new File(Environment.getExternalStorageDirectory(),"cache");
if(!cache.exists()){
cache.mkdirs();
}

//上页传下来的查询内容
Intent intent = new Intent();
intent = getIntent();
result = intent.getStringExtra("result"); setContentView(R.layout.view_list);  
listView = (ListView)findViewById(R.id.listView);
listView.setAdapter(new BookInfoAdapter(QueryResultActivity.this,getData(),R.layout.view_list_item,cache));  

}
/**
 * position 显示条目对应集合的索引值 convertView 对第一屏进行缓存
 */
@Override
public View getView(int position, View convertView, ViewGroup parent){ ImageView imageView = null;
TextView title_textView = null;
TextView price_textView = null;
TextView saleprice_textView = null;
// 第一屏的时候没有缓存
if (convertView == null) {
// resource viewListItem条目ID,即把条赋值给对象
convertView = layoutInflater.inflate(viewListItem, null);
// 创建条目时，先把各控件找到，否则每次去找耗性能
imageView = (ImageView) convertView.findViewById(R.id.imageView);
title_textView = (TextView) convertView.findViewById(R.id.title);
price_textView = (TextView) convertView.findViewById(R.id.price);
saleprice_textView = (TextView) convertView
.findViewById(R.id.saleprice); convertView.setTag(new DataWrapper(imageView, title_textView,
price_textView, saleprice_textView));
} else {
DataWrapper dataWrapper = (DataWrapper) convertView.getTag();
imageView = dataWrapper.imageView;
title_textView = dataWrapper.title_textView;
price_textView = dataWrapper.price_textView;
saleprice_textView = dataWrapper.saleprice_textView;
} title_textView.setText(data.get(position).get("title").toString());
price_textView.setText(data.get(position).get("price").toString());
saleprice_textView.setText(data.get(position).get("saleprice")
.toString());
try {
asyncImageLoad(imageView, data.get(position).get("imgurl").toString());
} catch (Exception e) {
e.printStackTrace();
} return convertView;
}