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)