数据适配器——BaseAdapter

可以自定义View或者利用参数中的convertView

一、逗比式

没有任何优化处理，每次都创建新的View，设置控件，效率极其低下

``` @Override

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

//逗比式(没有利用到ListView的缓存机制)//

View view = mInflater.inflate(R.layout.item,null);//装载到item中的布局文件

ImageView imageView = (ImageView) view.findViewById(R.id.iv_image);

TextView title = (TextView) view.findViewById(R.id.iv_title);

TextView content = (TextView) view.findViewById(R.id.iv_content);

ItemBean bean = mList.get(position);

imageView.setImageResource(bean.ItemImage);

title.setText(bean.ItemTitle);

content.setText(bean.ItemContent);

return view;

//逗比式//

}

二、普通式

-----

利用了ListView的缓存特性，如果没有缓存才创建新的View。算入门，但是findViewById依然会浪费大量时间

@Override

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

//普通式

if (convertView == null) {

convertView = mInflater.inflate(R.layout.item, null);

}

ImageView imageView = (ImageView) convertView.findViewById(R.id.iv_image);

TextView title = (TextView) convertView.findViewById(R.id.iv_title);

TextView content = (TextView) convertView.findViewById(R.id.iv_content);

ItemBean bean = mList.get(position);

imageView.setImageResource(bean.ItemImage);

title.setText(bean.ItemTitle);

content.setText(bean.ItemContent);

return content;

//普通式

三、文艺式

-----

不仅利用了ListView的缓存，更通过ViewHolder类来实现显示数据的视图的缓存，避免多次通过findViewById寻找控件(这是最号的写法)

1>创建内部类ViewHolder

2>判断convertView是否为空

3>通过setTag将ViewHolder与convertView绑定

//文艺式///

ViewHolder viewHolder;

if (convertView == null) {

viewHolder = new ViewHolder();

convertView = mInflater.inflate(R.layout.item, null);

viewHolder.imageView = (ImageView) convertView.findViewById(R.id.iv_image);

viewHolder.title = (TextView) convertView.findViewById(R.id.iv_title);

viewHolder.content = (TextView) convertView.findViewById(R.id.iv_content);

convertView.setTag(viewHolder);

} else {

viewHolder = (ViewHolder)convertView.getTag();

}

ItemBean bean = mList.get(position);

viewHolder.imageView.setImageResource(bean.ItemImage);

viewHolder.title.setText(bean.ItemTitle);

viewHolder.content.setText(bean.ItemContent);

return convertView;

//文艺式///

}

class ViewHolder {

public ImageView imageView;

public TextView title;

public TextView content;

}