ListView的优化

package com.example.list_youhua;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity {
private ListView lv1;
private List<String> list;

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv1 = (ListView) findViewById(R.id.listview);
list = new ArrayList<String>();
list.add("張飛");
list.add("劉備");
list.add("关羽");
list.add("張飛");
list.add("劉備");
list.add("关羽");
list.add("張飛");
list.add("劉備");
list.add("关羽");
list.add("張飛");
list.add("劉備");
list.add("关羽");
lv1.setAdapter(new basadapter(MainActivity.this));
}

class basadapter extends BaseAdapter {
private Context context;

public basadapter(Context context) {
this.context = context;
}

public int getCount() {
return list.size();
}

public Object getItem(int position) {
return list.get(position);
}

public long getItemId(int position) {
return position;
}

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

ViewHolder vh;
if (convertView == null) {
LayoutInflater inflater = LayoutInflater.from(context);
// 实例化一个布局组件
convertView = inflater.inflate(R.layout.list_item, null);

vh = new ViewHolder();
vh.tv = (TextView) convertView.findViewById(R.id.list_item_textView);

convertView.setTag(vh);
} else {

vh = (ViewHolder) convertView.getTag();

}

System.out.println("到底产生几个view" + convertView.getId());

vh.tv = (TextView) convertView
.findViewById(R.id.list_item_textView);
vh.tv.setText(list.get(position));
return convertView;
}

}

// 用于保存第一次查找的组件，避免下次重复查找
static class ViewHolder {
TextView tv;
}

}