Hello Android - SQLite数据库操作

        Android中内置的是SQLite小型数据库,类似access一样是以文件方式存在的,操作起来十分方便。android操作SQLite需要继承自SQLiteOpenHelper 来得到连接。实现了2个方法:onCreate和onUpgrade。第一次获得对数据库的读或写操作的时候调用onCreate,所以这里面写创建数据表的语句;在数据库版本变化的时候会调用onUpgrade,所以如果表结构变化了就在这里修改。

        下面的代码继承了SQLiteOpenHelper ,并且自己写了几个增删改查方法,将对数据库操作的DAO模块继承到一起,以后操作数据库用这一个java文件基本就OK啦。

package cn.itcast.service;import java.util.ArrayList;import java.util.List;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBOpenHelper extends SQLiteOpenHelper {private static final String DATABASENAME = "test.db"; //数据库名称private static final int DATABASEVERSION = 1;//数据库版本,大于0public DBOpenHelper(Context context) {super(context, DATABASENAME, null, DATABASEVERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL("CREATE TABLE person (personid integer primary key autoincrement, name varchar(20), amount integer)");//执行有更改的sql语句}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL("DROP TABLE IF EXISTS person");onCreate(db);}public void payment(){SQLiteDatabase db = getWritableDatabase();db.beginTransaction();//事启事务try{db.execSQL("update person set amount=amount-10 where personid=?", new Object[]{1});db.execSQL("update person set amount=amount+10 where personid=?", new Object[]{2});db.setTransactionSuccessful();//设置事务标志为成功，当结束事务时就会提交事务}finally{db.endTransaction();}}public void save(Person person){//如果要对数据进行更改，就调用此方法得到用于操作数据库的实例,该方法以读和写方式打开数据库SQLiteDatabase db = getWritableDatabase();db.execSQL("insert into person (name,amount) values(?,?)",new Object[]{person.getName(),person.getAmount()});}public void update(Person person){SQLiteDatabase db = getWritableDatabase();db.execSQL("update person set name=? where personid=?", new Object[]{person.getName(),person.getId()});}public void delete(Integer id){SQLiteDatabase db = getWritableDatabase();db.execSQL("delete from person where personid=?", new Object[]{id.toString()});}public Person find(Integer id){//如果只对数据进行读取，建议使用此方法SQLiteDatabase db = getReadableDatabase();Cursor cursor = db.rawQuery("select * from person where personid=?", new String[]{id.toString()});//得到游标if(cursor.moveToFirst()){int personid = cursor.getInt(cursor.getColumnIndex("personid"));String name = cursor.getString(cursor.getColumnIndex("name"));int amount = cursor.getInt(cursor.getColumnIndex("amount"));Person person = new Person(personid, name);person.setAmount(amount);return person;}return null;}public List<Person> getScrollData(Integer offset, Integer maxResult){List<Person> persons = new ArrayList<Person>();SQLiteDatabase db = getReadableDatabase();Cursor cursor = db.rawQuery("select * from person limit ?,?",new String[]{offset.toString(), maxResult.toString()});while(cursor.moveToNext()){int personid = cursor.getInt(cursor.getColumnIndex("personid"));String name = cursor.getString(cursor.getColumnIndex("name"));int amount = cursor.getInt(cursor.getColumnIndex("amount"));Person person = new Person(personid, name);person.setAmount(amount);persons.add(person);}cursor.close();return persons;}public Cursor getCursorScrollData(Integer offset, Integer maxResult){SQLiteDatabase db = getReadableDatabase();return db.rawQuery("select personid as _id, name, amount from person limit ?,?",new String[]{offset.toString(), maxResult.toString()});}public long getCount() {SQLiteDatabase db = getReadableDatabase();Cursor cursor = db.rawQuery("select count(*) from person", null);cursor.moveToFirst();return cursor.getLong(0);}}

涉及到的bean

class Person {private Integer id;private String name;private Integer amount;public Integer getAmount() {return amount;}public void setAmount(Integer amount) {this.amount = amount;}public Person(){}public Person(Integer id, String name) {this.id = id;this.name = name;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic String toString() {return "Person [amount=" + amount + ", id=" + id + ", name=" + name+ "]";}}