【初学安卓】微型数据库卡死

Question

在模拟器里还能运行，但是多次滚动后就会卡住。放在手机上就闪退。望高手给出指引。

这是MainActivity里的代码
package com.itheima.db;

import java.util.List;

import org.w3c.dom.Text;

import com.itheima.db.dao.PersonDao;
import com.itheima.db.domain.Person;

import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity {
private ListView lv;
private List persons;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    PersonDao dao = new PersonDao(this);
    persons = dao.findAll();
    lv = (ListView) findViewById(R.id.lv);
    lv.setAdapter(new MyAdapter());

}
//默认实现类 simpleXX defaultXX baseXX
private class MyAdapter extends BaseAdapter{
    /*
     * 控制listview里面总共的条目
     * */
    @Override
    public int getCount() {
        return persons.size();//条目个数 == 集合的size
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;
    }

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

        TextView tv = new TextView(getApplicationContext());
        tv.setTextSize(20);
        tv.setTextColor(Color.BLACK);
        //得到某个位置对应的person对象
        Person person = persons.get(position);
        tv.setText(person.toString());
        return tv;
    }

}

}

这是activity里面的代码

xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:id="@+id/ll_root"
tools:context=".MainActivity" >

<ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
</ListView>