在前文中总结了SQLite数据库的基本用法,本文中将使用SQLiteOpenHelper和单例模式来操作数据库。SQLiteOpenHelper是Android提供的一个管理数据库的工具类,可以用于管理数据库的创建和版本更新。一般的用法是创建它的子类,并扩展它的onCreate()和onUpgrade方法。
SQLiteOpenHelper包含如下方法:
同上文一样,数据仍是手动写死的,实际情况应该根据业务需求从界面或其他地方获取,实例代码如下,关键是后面两个类:
Activity:
[java]
view plain
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- packagecom.lovo.activity;
-
- importandroid.app.Activity;
- importandroid.database.Cursor;
- importandroid.os.Bundle;
- importandroid.view.View;
- importandroid.widget.TextView;
- importcom.lovo.dao.StuDao;
- importcom.lovo.databasetest.R;
-
- publicclassDatabaseTestActivityextendsActivity{
- privateTextViewshow;
- privateStuDaodao;
- @Override
- protectedvoidonCreate(BundlesavedInstanceState){
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- show=(TextView)findViewById(R.id.main_tv_show);
- dao=newStuDao(this);
- }
- voidclick(Viewv){
- switch(v.getId()){
- caseR.id.main_btn_insert:
-
- dao.insert("张三",24,"男");
- break;
- caseR.id.main_btn_delete:
- //根据指定ID删除数据
- dao.del(2);
- caseR.id.main_btn_update:
- //根据指定ID修改数据
- dao.update("王斌",0); background-color:inherit">34,"男",0); background-color:inherit">1);
- caseR.id.main_btn_find:
- StringBuffersb=newStringBuffer();
-
- Cursorcursor=dao.findAll();
- //根据指定ID查询数据
- //Cursorcursor=dao.findById(1);
- while(cursor.moveToNext()){
- intid=cursor.getInt(cursor.getColumnIndex("_id"));
- Stringname=cursor.getString(cursor.getColumnIndex("s_name"));
- Stringsex=cursor.getString(cursor.getColumnIndex("s_sex"));
- intage=cursor.getInt(cursor.getColumnIndex("s_age"));
- sb.append(id+""+name+""+sex+""+age+"n");
- }
- show.setText(sb.toString());
- break;
- }
布局XML:
[html]
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<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
- android:layout_width="match_parent"
- android:layout_height="match_parent"
- android:orientation="vertical">
- Button
- android:id="@+id/main_btn_insert"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:onClick="click"
- android:text="添加"/>
- Button
- android:id="@+id/main_btn_delete"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:onClick="click"
- android:text="删除"/>
- android:id="@+id/main_btn_update"
- android:text="修改" android:id="@+id/main_btn_find"
- android:text="查找"TextView
- android:id="@+id/main_tv_show"
- android:layout_height="wrap_content"</LinearLayout>
SQLiteOpenHelper的子类(DBUtil):
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packagecom.lovo.dao;
- importandroid.content.Context;
- importandroid.database.sqlite.SQLiteDatabase;
- importandroid.database.sqlite.SQLiteDatabase.CursorFactory;
- importandroid.database.sqlite.SQLiteOpenHelper;
- classDBUtilextendsSQLiteOpenHelper{
- privatestaticDBUtildbUtil;
- privateDBUtil(Contextcontext,Stringname,CursorFactoryfactory,
- intversion){
- super(context,name,factory,version);
- staticSQLiteDatabasegetInstance(Contextcontext){
- if(dbUtil==null){
- //指定数据库名为student,需修改时在此修改;此处使用默认工厂;指定版本为1
- dbUtil=newDBUtil(context,"student",null,153); background-color:inherit; font-weight:bold">returndbUtil.getReadableDatabase();
- voidonCreate(SQLiteDatabasedb){
- try{
- db.execSQL("createtablet_stu(_idintegerprimarykey,s_nametext,s_ageinteger,s_sextext)");
- }catch(Exceptione){
- e.printStackTrace();
- @Override
- voidonUpgrade(SQLiteDatabasedb,153); background-color:inherit; font-weight:bold">intoldVersion,153); background-color:inherit; font-weight:bold">intnewVersion){
- System.out.println("-----onUpgradeCalled-----"+oldVersion+"--->"
- +newVersion);
- }
StuDao类:封装数据操作的方法
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importandroid.database.sqlite.SQLiteDatabase;
- classStuDao{
- privateSQLiteDatabasedb;
- publicStuDao(Contextcontext){
- db=DBUtil.getInstance(context);
- /**
- *查询所有数据
- *
- *@returnCursor
- */
- publicCursorfindAll(){
- Cursorcursor=db.rawQuery("select*fromt_stu",153); background-color:inherit; font-weight:bold">null);
- returncursor;
- *添加数据
- *@paramname姓名
- *@paramage年龄
- *@paramsex性别
- voidinsert(Stringname,153); background-color:inherit; font-weight:bold">intage,Stringsex){
- db.execSQL("insertintot_stuvalues(null,?,?)",153); background-color:inherit; font-weight:bold">newString[]{name,
- age+"",sex});
- *删除数据
- *@paramid
- voiddel(intid){
- db.execSQL("deletefromt_stuwhere_id=?",153); background-color:inherit; font-weight:bold">newString[]{id+""});
- /**
- *根据id查询数据
- *
- *@paramid
- publicCursorfindById( Cursorcursor=db.rawQuery("select*fromt_stuwhere_id=?",153); background-color:inherit; font-weight:bold">newString[]{id+""});
- returncursor;
- *修改数据
- *@paramname姓名
- *@paramage年龄
- *@paramsex性别
- *@paramidid
- voidupdate(Stringname,Stringsex,248); line-height:17.600000381469727px; margin:0px!important; padding:0px 3px 0px 10px!important"> db.execSQL("updatet_stusets_name=?,s_age=?,s_sex=?where_id=?",153); background-color:inherit; font-weight:bold">newObject[]{name,age,sex,id});
- }
(编辑:李大同)
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