android数据库升级（一）

来源：互联网发布：淘宝品牌授权资质编辑：程序博客网时间：2024/04/28 16:25

一、定义一个adress的实体类

package com.databasetest;

public class Address {
public int id;
public String address;
public String province;
@Override
public String toString() {
return "Address [id=" + id + ", address=" + address + ", province="
+ province + "]";
}

}

二、定义helper

package com.databasetest;

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

public class AddressDBHelper extends SQLiteOpenHelper{

   private static SQLiteOpenHelper mInstance;

   private final static String name = "AddressDBHelper.db";

   public static SQLiteOpenHelper getInstance(Context context){
       if(mInstance == null){

//3与1版本不同会调用升级方法
           mInstance = new AddressDBHelper(context, name, null, 3);
       }
       return mInstance;
   }


   public AddressDBHelper(Context context, String name, CursorFactory factory,
           int version) {

//通过修改version值来通知调用升级程序
       super(context, name, factory, 1);
       // TODO Auto-generated constructor stub
   }

   @Override
   public void onCreate(SQLiteDatabase db) {
       db.execSQL("create table address(_id integer primary key autoincrement,address text)");

   }
//如果构造方法的version值与已经存在的不同则条用此方法
   @Override
   public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
       db.beginTransaction();


                try {
                   db.execSQL("Alter Table address ADD COLUMN province text");
                   // Create tables
                   db.setTransactionSuccessful();
               } catch (SQLException e) {
                   // TODO Auto-generated catch block
                   e.printStackTrace();
               }
           db.endTransaction();


   }

}

三、写一个dao类进行增删改查

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

public class AddressDao {
   private SQLiteOpenHelper mOpenHelper;

   public AddressDao(Context context) {
       super();
       this.mOpenHelper = AddressDBHelper.getInstance(context);
   }

   public void add(String address){
       SQLiteDatabase db = mOpenHelper.getWritableDatabase();
       db.beginTransaction();
       try {
           if(db.isOpen()){
               ContentValues values = new ContentValues();
               values.put("address", address);
               db.insert("address", "", values);
               db.setTransactionSuccessful();
           }
       } catch (Exception e) {

       }finally{
           db.endTransaction();

       }
       db.close();
   }

   public void deleteById(int id){
       SQLiteDatabase db = mOpenHelper.getWritableDatabase();
       db.beginTransaction();
       try {
           if(db.isOpen()){
               db.delete("address", " _id = ? ", new String[]{id + ""});
               db.setTransactionSuccessful();
           }
       }catch (Exception e) {

       }finally{
           db.endTransaction();

       }
       db.close();
   }

   public Address findAddressById(int id){
       SQLiteDatabase db = mOpenHelper.getReadableDatabase();
       Address address = null;
       try {
           if(db.isOpen()){
               Cursor c = db.query("address", new String[]{"_id","address"},
                       "_id=?",new String[]{id+""},
                       null, null, null);
               if(c.moveToNext()){
                   address = new Address();
                   address.id = c.getInt(c.getColumnIndex("_id"));
                   address.address = c.getString(c.getColumnIndex("address"));
               }
           }
       } catch (Exception e) {

       }
       db.close();
       return address;
   }

   public List<Address> findAll(){
       SQLiteDatabase db = mOpenHelper.getReadableDatabase();
       List<Address> ads = new ArrayList<Address>();
       Address address = null;
       if(db.isOpen()){
           Cursor c = db.query("address", new String[]{"_id","address"},
                   null, null, null, null, null, null);
           while(c.moveToNext()){
               address = new Address();
               address.id = c.getInt(c.getColumnIndex("_id"));
               address.address = c.getString(c.getColumnIndex("address"));
               ads.add(address);
           }
       }
       db.close();
       return ads;
   }
}

0 0