每次滑动至底端，从数据库中获取10条数据，并加载于ListView中
数据库
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package com.example.listviewbatchloading; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; public class PersonDb extends SQLiteOpenHelper { public PersonDb(Context context) { super(context, "creature", null, 1); // TODO Auto-generated constructor stub } @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub db.execSQL("create table people(_id integer primary key autoincrement,name char,number char)"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub db.execSQL("drop table people"); onCreate(db); } } |
数据库的业务封装，其中获取更多数据的是核心代码
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package com.example.listviewbatchloading; /** * 数据库的业务封装类 */ import java.util.ArrayList; import java.util.List; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; public class PersonList { PersonDb personDb; public PersonList(Context context){ this.personDb = new PersonDb(context); } /** * 获取一定条目的数据 * @param startIndex * 开始取数据的位置 * @param num * 取多少条数据 */ public List<Person> getMoreDatas(int startIndex,int num){ List<Person> list = new ArrayList<Person>(); SQLiteDatabase db = personDb.getWritableDatabase(); Cursor cursor = db.rawQuery("select name,number from people order by _id desc limit ?,?", new String[]{startIndex + "",num + ""}); while(cursor.moveToNext()){ Person person = new Person(); person.setName(cursor.getString(cursor.getColumnIndex("name"))); person.setNumber(cursor.getString(cursor.getColumnIndex("number"))); list.add(person); } cursor.close(); db.close(); return list; } /** * 添加数据库条目 * @param name * @param number */ public void add(String name,String number){ SQLiteDatabase db = personDb.getWritableDatabase(); ContentValues cv = new ContentValues(); cv.put("name", name); cv.put("number", number); db.insert("people", null, cv); db.close(); } } |
功能实现
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package com.example.listviewbatchloading; import java.util.ArrayList; import java.util.List; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.view.ViewGroup; import android.widget.AbsListView; import android.widget.AbsListView.OnScrollListener; import android.widget.BaseAdapter; import android.widget.ListView; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends Activity { private ListView lv ; private List<Person> datas = new ArrayList<Person>(); private static int PERPAGE = 10; //每页加载数目 private static final int FINISH = 0;//数据加载完成 private List<Person> moreDatas;//每次加载的数据 private MyAdapter adapter; private PersonList personList ; //若数据较多，耗时较长，数据加载完成时，发送FINISH至handler，并通知ListView更新数据 private Handler handler = new Handler(){ public void handleMessage(android.os.Message msg) { switch (msg.what) { case FINISH: if (moreDatas.size() != 0) { System.out.println(moreDatas.toString()); adapter.notifyDataSetChanged(); }else { Toast.makeText(MainActivity.this, "没有更多数据", Toast.LENGTH_SHORT).show(); } break; default: break; } }; }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView(); initData(); initEvent(); } /** * 为ListView添加滚动监听事件，但滚动至最后一行时，加载更多数据 */ private void initEvent() { lv.setOnScrollListener(new OnScrollListener() { @Override public void onScrollStateChanged(AbsListView view, int scrollState) { // TODO Auto-generated method stub if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) { int lastVisiblePosition = lv.getLastVisiblePosition(); if (lastVisiblePosition == datas.size() - 1) { initData(); System.out.println("加载更多数据"); } } } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { // TODO Auto-generated method stub } }); } private void initView() { setContentView(R.layout.activity_main); lv = (ListView) findViewById(R.id.lv); personList = new PersonList(getApplicationContext()); adapter = new MyAdapter(); lv.setAdapter(adapter); } /** * 在子线程中加载数据，避免主线程阻塞 */ private void initData() { new Thread() { public void run() { // 加载更多数据 moreDatas = personList.getMoreDatas(datas.size(), PERPAGE); datas.addAll(moreDatas);// 把一个容器的所有数据加进来 // 取数据完成，发消息通知取数据完成 handler.obtainMessage(FINISH).sendToTarget(); }; }.start(); } private class ItemView{ private TextView tv_name; private TextView tv_num; } /** * ListView的适配器 * @author lian * */ private class MyAdapter extends BaseAdapter{ @Override public int getCount() { // TODO Auto-generated method stub return datas.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) { ItemView itemView = null; if (convertView == null) { itemView = new ItemView(); convertView = View.inflate(getApplicationContext(), R.layout.item_lv, null); itemView.tv_name = (TextView) convertView.findViewById(R.id.tv_name); itemView.tv_num = (TextView) convertView.findViewById(R.id.tv_num); convertView.setTag(itemView); }else { itemView = (ItemView) convertView.getTag(); } Person person = datas.get(position); itemView.tv_name.setText(person.getName()); itemView.tv_num.setText(person.getNumber()); return convertView; } } } |
其他Person的JavaBean，以及布局文件，不在赘述
以上就是本文的全部内容，希望对大家的学习有所帮助。
