android listview scroll滑屏显示sqlite分页，类似聊天记录，listview动态添加sqlite分页数据

前言：最近做基于openfire聊天(仿QQ、微信)翻页查看聊天记录，为此做了根据时间倒序查看聊天记录，先声明这demo是根据id来倒序(原理和时间倒序一样)

public class MainActivity extends Activity implements OnScrollListener{
private ProgressBar loadInfo;
private ListView listView;
private LinearLayout loadLayout;
private ArrayList<String> items;
private DatabaseService service;
private int currentPage = 1; //默认在第一页
private static final int lineSize =10;    //每次显示数
private int allRecorders = 0;  //全部记录数
private int pageSize = 1;  //默认共一页
private Aleph0 baseAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listview);
service = new DatabaseService(this);
//创建一个角标线性布局用来显示"正在加载"
loadLayout = new LinearLayout(this);
loadLayout.setGravity(Gravity.CENTER);
//定义一个ProgressBar表示“正在加载”
loadInfo = new ProgressBar(this,null,android.R.attr.progressBarStyleSmall);
//增加组件
loadLayout.addView(loadInfo, new LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
//增加到listView头部
listView.addHeaderView(loadLayout);
listView.setOnScrollListener(this);

showAllData();

}

/**
* 读取全部数据
*/
public void showAllData(){

allRecorders = service.getCount();
//计算总页数
pageSize = (allRecorders + lineSize -1) / lineSize;
items = service.getAllItems(currentPage, lineSize);
Collections.reverse(items);  //倒序
baseAdapter = new Aleph0();
listView.setAdapter(baseAdapter);
listView.setSelection(items.size());//直接定位到最底部
}
int firstItem=-1;

@Override
public void onScroll(AbsListView absView, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
firstItem=firstVisibleItem;
}
@Override
public void onScrollStateChanged(AbsListView view, int scorllState) {
if (firstItem==0&& currentPage < pageSize&& scorllState == OnScrollListener.SCROLL_STATE_IDLE) {// 不再滚动
Log.e("log", "滑到第一位");
currentPage++;
// 增加数据
appendDate();
}
}

/**
* 增加数据
*/
private void appendDate(){
final ArrayList<String> additems = service.getAllItems(currentPage, lineSize);
Collections.reverse(additems);
baseAdapter.setCount(baseAdapter.getCount() + additems.size());
//判断，如果到了最末尾则去掉“正在加载”
if(allRecorders == baseAdapter.getCount()){
listView.removeHeaderView(loadLayout);
}
items.addAll(0, additems);

baseAdapter.notifyDataSetChanged();
listView.setSelection(additems.size());

}

class Aleph0 extends BaseAdapter {
int count = lineSize;

public int getCount() {
return count;
}

public void setCount(int count){
this.count = count;
}

public Object getItem(int pos) {
return pos;
}

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

public View getView(int pos, View v, ViewGroup p) {
TextView view = new TextView(MainActivity.this);
view.setTextSize(60);
if(items != null){
view.setText(items.get(pos));
}else{
view.setText(pos);
}
return view;
}
}

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<ListView
android:id="@+id/listview"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />

</LinearLayout>

public class DatabaseService {

private Context mContext;
private MyDBOpenHelper dbHelper;

public DatabaseService(Context context) {
mContext = context;
dbHelper = new MyDBOpenHelper(mContext);
}

// 添加
public void insert(String title) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "insert into database(title) values(?)";
db.execSQL(sql, new String[] { title });
}

// 删除
public void delete(String title) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "delete from database where title = ?";
db.execSQL(sql, new String[] { title });
}

// 查找
public ArrayList<String> find(int id) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "select * from database where _id = ? ";
Cursor c = db.rawQuery(sql, new String[] { String.valueOf(id) });
ArrayList<String> titles = new ArrayList<String>();
if (c.moveToNext()) {
String title = c.getString(c
.getColumnIndexOrThrow(MyDBOpenHelper.FIELD_TITLE));
titles.add(title);
return titles;
}
// 不用忘记关闭Cursor。
c.close();
return null;
}

// 更新
public void upDate(int id, String title) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "update database set title =? where _id = ?";
db.execSQL(sql,
new String[] { String.valueOf(title), String.valueOf(id) });
}

// 查询记录的总数
public int getCount() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "select count(*) from database";
Cursor c = db.rawQuery(sql, null);
c.moveToFirst();
int length = c.getInt(0);
c.close();
return length;
}

/**
* 分页查询
*
* @param currentPage 当前页
* @param pageSize 每页显示的记录
* @return 当前页的记录
*/
public ArrayList<String> getAllItems(int currentPage, int pageSize) {
int firstResult = (currentPage - 1) * pageSize;
int maxResult = currentPage * pageSize;
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "select * from database order by  _id desc limit ?,? ";
Cursor mCursor = db.rawQuery(
sql,
new String[] { String.valueOf(firstResult),
String.valueOf(pageSize) });
ArrayList<String> items = new ArrayList<String>();
int columnCount  = mCursor.getColumnCount();
while (mCursor.moveToNext()) {
String item = mCursor.getString(mCursor
.getColumnIndexOrThrow(MyDBOpenHelper.FIELD_TITLE));
items.add(item);

}
//不要关闭数据库
return items;
}
}