安卓中SQLite数据库操作学习

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0

     public DBOpenHelper(Context context) {
         super(context, DATABASENAME, null, DATABASEVERSION);
     }

     @Override
     public 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
     }

     @Override
     public 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;
     }

     @Override
     public String toString() {
         return "Person [amount=" + amount + ", id=" + id + ", name=" + name
                 + "]";
     }


 }

摘自：http://www.apkbus.com/blog-58672-39951.html