Android实现简单的分批加载ListView
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
packagecom.example.listviewbatchloading;
importandroid.content.Context;
importandroid.database.sqlite.SQLiteDatabase;
importandroid.database.sqlite.SQLiteDatabase.CursorFactory;
importandroid.database.sqlite.SQLiteOpenHelper;
publicclassPersonDbextendsSQLiteOpenHelper{
publicPersonDb(Contextcontext){
super(context,"creature",null,1);
//TODOAuto-generatedconstructorstub
}
@Override
publicvoidonCreate(SQLiteDatabasedb){
//TODOAuto-generatedmethodstub
db.execSQL("createtablepeople(_idintegerprimarykeyautoincrement,namechar,numberchar)");
}
@Override
publicvoidonUpgrade(SQLiteDatabasedb,intoldVersion,intnewVersion){
//TODOAuto-generatedmethodstub
db.execSQL("droptablepeople");
onCreate(db);
}
}
数据库的业务封装，其中获取更多数据的是核心代码
packagecom.example.listviewbatchloading;
/**
*数据库的业务封装类
*/
importjava.util.ArrayList;
importjava.util.List;
importandroid.content.ContentValues;
importandroid.content.Context;
importandroid.database.Cursor;
importandroid.database.sqlite.SQLiteDatabase;
publicclassPersonList{
PersonDbpersonDb;
publicPersonList(Contextcontext){
this.personDb=newPersonDb(context);
}
/**
*获取一定条目的数据
*@paramstartIndex
*开始取数据的位置
*@paramnum
*取多少条数据
*/
publicList<Person>getMoreDatas(intstartIndex,intnum){
List<Person>list=newArrayList<Person>();
SQLiteDatabasedb=personDb.getWritableDatabase();
Cursorcursor=db.rawQuery("selectname,numberfrompeopleorderby_iddesclimit?,?",
newString[]{startIndex+"",num+""});
while(cursor.moveToNext()){
Personperson=newPerson();
person.setName(cursor.getString(cursor.getColumnIndex("name")));
person.setNumber(cursor.getString(cursor.getColumnIndex("number")));
list.add(person);
}
cursor.close();
db.close();
returnlist;
}
/**
*添加数据库条目
*@paramname
*@paramnumber
*/
publicvoidadd(Stringname,Stringnumber){
SQLiteDatabasedb=personDb.getWritableDatabase();
ContentValuescv=newContentValues();
cv.put("name",name);
cv.put("number",number);
db.insert("people",null,cv);
db.close();
}
}
功能实现
packagecom.example.listviewbatchloading;
importjava.util.ArrayList;
importjava.util.List;
importandroid.app.Activity;
importandroid.os.Bundle;
importandroid.os.Handler;
importandroid.os.Message;
importandroid.view.View;
importandroid.view.ViewGroup;
importandroid.widget.AbsListView;
importandroid.widget.AbsListView.OnScrollListener;
importandroid.widget.BaseAdapter;
importandroid.widget.ListView;
importandroid.widget.TextView;
importandroid.widget.Toast;
publicclassMainActivityextendsActivity{
privateListViewlv;
privateList<Person>datas=newArrayList<Person>();
privatestaticintPERPAGE=10;//每页加载数目
privatestaticfinalintFINISH=0;//数据加载完成
privateList<Person>moreDatas;//每次加载的数据
privateMyAdapteradapter;
privatePersonListpersonList;
//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
privateHandlerhandler=newHandler(){
publicvoidhandleMessage(android.os.Messagemsg){
switch(msg.what){
caseFINISH:
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
protectedvoidonCreate(BundlesavedInstanceState){
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
*/
privatevoidinitEvent(){
lv.setOnScrollListener(newOnScrollListener(){
@Override
publicvoidonScrollStateChanged(AbsListViewview,intscrollState){
//TODOAuto-generatedmethodstub
if(scrollState==OnScrollListener.SCROLL_STATE_IDLE){
intlastVisiblePosition=lv.getLastVisiblePosition();
if(lastVisiblePosition==datas.size()-1){
initData();
System.out.println("加载更多数据");
}
}
}
@Override
publicvoidonScroll(AbsListViewview,intfirstVisibleItem,intvisibleItemCount,inttotalItemCount){
//TODOAuto-generatedmethodstub
}
});
}
privatevoidinitView(){
setContentView(R.layout.activity_main);
lv=(ListView)findViewById(R.id.lv);
personList=newPersonList(getApplicationContext());
adapter=newMyAdapter();
lv.setAdapter(adapter);
}
/**
*在子线程中加载数据，避免主线程阻塞
*/
privatevoidinitData(){
newThread(){
publicvoidrun(){
//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();
}
privateclassItemView{
privateTextViewtv_name;
privateTextViewtv_num;
}
/**
*ListView的适配器
*@authorlian
*
*/
privateclassMyAdapterextendsBaseAdapter{
@Override
publicintgetCount(){
//TODOAuto-generatedmethodstub
returndatas.size();
}
@Override
publicObjectgetItem(intposition){
//TODOAuto-generatedmethodstub
returnnull;
}
@Override
publiclonggetItemId(intposition){
//TODOAuto-generatedmethodstub
return0;
}
@Override
publicViewgetView(intposition,ViewconvertView,ViewGroupparent){
ItemViewitemView=null;
if(convertView==null){
itemView=newItemView();
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();
}
Personperson=datas.get(position);
itemView.tv_name.setText(person.getName());
itemView.tv_num.setText(person.getNumber());
returnconvertView;
}
}
}
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。