android 数据库的增删改查

package com.itheima.crud;

import android.app.Activity;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;

import com.itheima.crud.R;
import com.itheima.crud.bean.InfoBean;
import com.itheima.crud.dao.InfoDao;

public class MainActivity extends Activity implements OnClickListener {

    private Context mContext;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mContext = this;
        //创建一个帮助类对象
        MySqliteOpenHelper mySqliteOpenHelper = new MySqliteOpenHelper(mContext);
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();


        //找到相应控件
        findViewById(R.id.bt_add).setOnClickListener(this);

        findViewById(R.id.bt_del).setOnClickListener(this);
        findViewById(R.id.bt_update).setOnClickListener(this);
        findViewById(R.id.bt_query).setOnClickListener(this);

    }
    @Override
    public void onClick(View v) {
        InfoDao infoDao = new InfoDao(mContext);//创建一个dao对象做增删改查

        switch (v.getId()) {
        case R.id.bt_add:
            
            InfoBean bean = new InfoBean();
            bean.name = "张三";
            bean.phone ="110";
            infoDao.add(bean);
            
            InfoBean bean1 = new InfoBean();
            bean1.name = "李四";
            bean1.phone ="120";
            infoDao.add(bean1);
            break;

        case R.id.bt_del:
            
            infoDao.del("张三");
            break;

        case R.id.bt_update:
            
            InfoBean bean2 = new InfoBean();
            bean2.name = "张三";
            bean2.phone ="119";
            infoDao.update(bean2);
            break;


        case R.id.bt_query:
            infoDao.query("张三");
            infoDao.query("李四");
            break;

        default:
            break;
        }

    }




}

package com.itheima.crud;

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

public class MySqliteOpenHelper extends SQLiteOpenHelper {

    public MySqliteOpenHelper(Context context) {
        
        //context :上下文   ， name：数据库文件的名称    factory：用来创建cursor对象，默认为null 
        //version:数据库的版本号，从1开始，如果发生改变，onUpgrade方法将会调用,4.0之后只能升不能将
        super(context, "info.db", null,1);
    }

    //oncreate方法是数据库第一次创建的时候会被调用;  特别适合做表结构的初始化,需要执行sql语句；SQLiteDatabase db可以用来执行sql语句
    @Override
    public void onCreate(SQLiteDatabase db) {
        //通过SQLiteDatabase执行一个创建表的sql语句
        db.execSQL("create table info (_id integer primary key autoincrement,name varchar(20),phone varchar(11))");
    }

    //onUpgrade数据库版本号发生改变时才会执行； 特别适合做表结构的修改
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        //添加一个phone字段
//        db.execSQL("alter table info add phone varchar(11)");
    }

}

package com.itheima.crud.dao;

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

import com.itheima.crud.MySqliteOpenHelper;
import com.itheima.crud.bean.InfoBean;

public class InfoDao {


    private MySqliteOpenHelper mySqliteOpenHelper;
    public InfoDao(Context context){
        //创建一个帮助类对象
        mySqliteOpenHelper = new MySqliteOpenHelper(context);

        
    }

    public void add(InfoBean bean){

        //执行sql语句需要sqliteDatabase对象
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase     db = mySqliteOpenHelper.getWritableDatabase();
        //sql:sql语句，  bindArgs：sql语句中占位符的值
        db.execSQL("insert into info(name,phone) values(?,?);", new Object[]{bean.name,bean.phone});
        //关闭数据库对象
        db.close();
    }

    public void del(String name){


        //执行sql语句需要sqliteDatabase对象
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();
        //sql:sql语句，  bindArgs：sql语句中占位符的值
        db.execSQL("delete from info where name=?;", new Object[]{name});
        //关闭数据库对象
        db.close();

    }
    public void update(InfoBean bean){

        //执行sql语句需要sqliteDatabase对象
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();
        //sql:sql语句，  bindArgs：sql语句中占位符的值
        db.execSQL("update info set phone=? where name=?;", new Object[]{bean.phone,bean.name});
        //关闭数据库对象
        db.close();

    }
    public void query(String name){
    
        //执行sql语句需要sqliteDatabase对象
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();
        //sql:sql语句，  selectionArgs:查询条件占位符的值,返回一个cursor对象
        Cursor cursor = db.rawQuery("select _id, name,phone from info where name = ?;", new String []{name});
        //解析Cursor中的数据
        if(cursor != null && cursor.getCount() >0){//判断cursor中是否存在数据
            
            //循环遍历结果集，获取每一行的内容
            while(cursor.moveToNext()){//条件，游标能否定位到下一行
                //获取数据
                int id = cursor.getInt(0);
                String name_str = cursor.getString(1);
                String phone = cursor.getString(2);
                System.out.println("_id:"+id+";name:"+name_str+";phone:"+phone);
            }
            cursor.close();//关闭结果集
            
        }
        //关闭数据库对象
        db.close();

    }
}

package com.itheima.crud.dao;

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

import com.itheima.crud.MySqliteOpenHelper;
import com.itheima.crud.bean.InfoBean;

public class InfoDao {


    private MySqliteOpenHelper mySqliteOpenHelper;
    public InfoDao(Context context){
        //创建一个帮助类对象
        mySqliteOpenHelper = new MySqliteOpenHelper(context);

        
    }

    public void add(InfoBean bean){

        //执行sql语句需要sqliteDatabase对象
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase     db = mySqliteOpenHelper.getWritableDatabase();
        //sql:sql语句，  bindArgs：sql语句中占位符的值
        db.execSQL("insert into info(name,phone) values(?,?);", new Object[]{bean.name,bean.phone});
        //关闭数据库对象
        db.close();
    }

    public void del(String name){


        //执行sql语句需要sqliteDatabase对象
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();
        //sql:sql语句，  bindArgs：sql语句中占位符的值
        db.execSQL("delete from info where name=?;", new Object[]{name});
        //关闭数据库对象
        db.close();

    }
    public void update(InfoBean bean){

        //执行sql语句需要sqliteDatabase对象
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();
        //sql:sql语句，  bindArgs：sql语句中占位符的值
        db.execSQL("update info set phone=? where name=?;", new Object[]{bean.phone,bean.name});
        //关闭数据库对象
        db.close();

    }
    public void query(String name){
    
        //执行sql语句需要sqliteDatabase对象
        //调用getReadableDatabase方法,来初始化数据库的创建
        SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();
        //sql:sql语句，  selectionArgs:查询条件占位符的值,返回一个cursor对象
        Cursor cursor = db.rawQuery("select _id, name,phone from info where name = ?;", new String []{name});
        //解析Cursor中的数据
        if(cursor != null && cursor.getCount() >0){//判断cursor中是否存在数据
            
            //循环遍历结果集，获取每一行的内容
            while(cursor.moveToNext()){//条件，游标能否定位到下一行
                //获取数据
                int id = cursor.getInt(0);
                String name_str = cursor.getString(1);
                String phone = cursor.getString(2);
                System.out.println("_id:"+id+";name:"+name_str+";phone:"+phone);
            }
            cursor.close();//关闭结果集
            
        }
        //关闭数据库对象
        db.close();

    }
}

<?xml version="1.0"?>

-<LinearLayout tools:context=".MainActivity" android:orientation="vertical" android:paddingTop="@dimen/activity_vertical_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingBottom="@dimen/activity_vertical_margin" android:layout_height="match_parent" android:layout_width="match_parent" xmlns:tools="http://schemas.android.com/tools" xmlns:android="http://schemas.android.com/apk/res/android">

<Button android:id="@+id/bt_add" android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/add"/>

<Button android:id="@+id/bt_del" android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/del"/>

<Button android:id="@+id/bt_update" android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/update"/>

<Button android:id="@+id/bt_query" android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/query"/>

</LinearLayout>