SQLiteDatabase 和 SQLiteOpenHelper

SQLiteDatabase类可以执行SQL语句，对数据库进行增删改查。

SQLiteOpenHelper是一个辅助类，帮助SQLiteDatabase获取对数据库的操作权。它有两个重写的方法，一个是onCreate()创建数据库，另一个是OnUpgrage() 用户升级数据库使用

实例：

1.写一个SQLiteOpenHelper创建数据库：

创建数据的sql语句模式是：

名称的数据格式需要注意，特别是text类需要在使用的时候添加单引号，否则报错；

未免这种错失，可以使用占位符方式，看例子2

create table  XX （XX integer primary key autoincrement,XX text not null,XX integer not null）

package com.man.SQLiteDemoOne;

import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;

public class DBhelper extends SQLiteOpenHelper {

public DBhelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {            super(context, name, factory, 1);      }

@Override      public void onCreate(SQLiteDatabase db) {

db.execSQL("create table if not exists demo(_id integer primary key autoincrement,name text not null, age integer not null)");            db.execSQL("insert into demo(name,age)values(‘Tom‘,25)");      }

@Override      public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

db.execSQL("drop table if exists demo");            onCreate(db);      }}

2.写一个增删改查的类以及其中的方法：

注意，text的引号使用

package com.man.SQLiteDemoOne;

import android.database.sqlite.SQLiteDatabase;

public class MyOperation {

private SQLiteDatabase db = null;

public MyOperation(SQLiteDatabase db) {

this.db = db;      }

public void insertData(String name, int age) {

db.execSQL("insert into demo (name,age) values(‘"+name+"‘,"+age+")");      }

public void deleteData(int id){

db.execSQL("delete from demo where _id="+id);      }

public void updateData(int id,String name ,int age){

db.execSQL("update demo set name=‘" + name+"‘,age=" + age + " where _id=" + id);      }

}

3.在main类中调用：

package com.man.SQLiteDemoOne;

import android.app.Activity;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;

public class MyActivity extends Activity {

@Override      public void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentView(R.layout.main);

DBhelper helper = new DBhelper(MyActivity.this, "dog.db", null, 1);            SQLiteDatabase db = helper.getWritableDatabase();            MyOperation operation = new MyOperation(db);

operation.updateData(10, "change", 55);            operation.deleteData(15);            operation.deleteData(14);            db.close();

}}

例子二：为了避免使用string的标点符号导致sql语句错误，用占位符

package com.example.SQlistDemoTwo;

import android.database.sqlite.SQLiteDatabase;

public class Methodss {

private SQLiteDatabase db;

public Methodss(SQLiteDatabase db) {            this.db = db;      }

public void insertData(String name,int age) {

Object[] item = new Object[]{name,age};            db.execSQL("insert into stu(name,age) values(?,?)",item);      }

public void updateData(int id,String name,int age){

Object[] items = new Object[]{name, age, id};            db.execSQL("update stu set name=?,age=? where id=?",items);      }

public void deleteData(int id) {

Object[] items = new Object[]{id};            db.execSQL("delete from stu where id=?",items);      }}

来自为知笔记(Wiz)