安卓：查询sqlite数据库中的数据，分页加载显示出来

<span style="font-size:18px;">package com.example.day14_pageload;

import java.io.File;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.SimpleAdapter;

public class MainActivity extends Activity {

ListView lv;
RelativeLayout rl;
SQLiteDatabase db;
SimpleAdapter adapter;
List<Map<String, Object>> list ;
int totalNum;//数据总条数
int pageSize=15;//每页显示的条数
int totalPage;//总的页数
int currentPage=1;//当前页码
boolean isbottom=false;//判断是否到当前页码的底部
String path = Environment.getExternalStorageDirectory().
getAbsolutePath()+File.separator+"Download"+File.separator+"test.db";

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv=(ListView) findViewById(R.id.lv);
rl=(RelativeLayout) findViewById(R.id.rl);
db=SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READWRITE);
String sql="select * from person";
Cursor c=db.rawQuery(sql, null);
totalNum=c.getCount();
totalPage=(int)Math.ceil((totalNum/pageSize));
if(1==currentPage)
{
getData(currentPage);
}

adapter=new SimpleAdapter(getApplicationContext(),list, R.layout.style, new String[] {
"name", "sex", "age", "love" }, new int[] { R.id.name,
R.id.sex, R.id.age, R.id.love });
lv.setAdapter(adapter);
lv.setOnScrollListener(new OnScrollListener() {

@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if(isbottom&&(scrollState == OnScrollListener.SCROLL_STATE_IDLE))
{
rl.setVisibility(View.VISIBLE);
}
else
{
rl.setVisibility(View.GONE);
}
}

@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
isbottom=((firstVisibleItem+visibleItemCount)==totalItemCount);
}
});

}
//点击加载更多的监听事件
public void click(View v)
{
currentPage++;
list.addAll(getData(currentPage));
adapter.notifyDataSetChanged();
rl.setVisibility(View.GONE);
}
//获取当前页的数据
@SuppressLint("NewApi")
public List<Map<String, Object>>  getData(int currentPage){
int index = (currentPage-1)*pageSize;//0   0   1  20   2  40
String sql = "select * from person limit ?,?";//从哪一个位置    请求多少条
Cursor c = db.rawQuery(sql, new String[]{index+"",pageSize+""});
return getCursorList(c);

}
@SuppressLint("NewApi")
public List<Map<String, Object>> getCursorList(Cursor c){
list = new ArrayList<Map<String,Object>>();
String[] coloms = c.getColumnNames();//[_id,name] 有多少字段项
while(c.moveToNext()){
Map<String, Object> map = new HashMap<String, Object>();
for(int i=0;i<coloms.length;i++){
String key = coloms[i];
Object values = null;
int type = c.getType(i);
switch (type) {
case Cursor.FIELD_TYPE_BLOB:
values = c.getBlob(i);
break;
case Cursor.FIELD_TYPE_FLOAT:
values = c.getFloat(i);
break;
case Cursor.FIELD_TYPE_INTEGER:
values = c.getInt(i);
break;
case Cursor.FIELD_TYPE_STRING:
values = c.getString(i);
break;

default:
break;
}
map.put(key, values);
}

list.add(map);
}

return list;

}

}
</span>

<span style="font-size:18px;"><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<RelativeLayout
android:layout_alignParentBottom="true"
android:id="@+id/rl"
android:layout_width="match_parent"
android:layout_height="50dp"
android:onClick="click"
android:gravity="center"
android:visibility="gone">
<ProgressBar
android:id="@+id/pb"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="加载更多"
android:gravity="center"
android:layout_toRightOf="@id/pb"/>
</RelativeLayout>

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

</RelativeLayout>
</span>

<span style="font-size:18px;"><?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#00ff00"
android:textSize="28sp"/>
<TextView
android:id="@+id/sex"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#00ff00"
android:textSize="28sp"/>
<TextView
android:id="@+id/age"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#00ff00"
android:textSize="28sp"/>
<TextView
android:id="@+id/love"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#00ff00"
android:textSize="28sp"/>

</LinearLayout>
</span>