安卓基础之Sqlite数据库最最基础操作

Posted 2021-01-24 Addressian

Sqlite数据库基础操作

 

摘要:在应用中新建一个数据库,并创建一个数据表写入数据,然后读取表中数据并展示.

 

主要逻辑:

1.通过继承SQLiteOpenHelper自定义类,定制数据库的表结构,初始化,升级操作

2.实例化SQLiteOpenHelper,通过getReadableDatabase()创建数据库并且获取SQLiteDatabase示例

3.SQLiteDatabase的示例后可以实现对数据库的多种操作,如查询库中的表信息

 

一.新建一个类继承SQLiteOpenHelper

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

public class MyOpenHelper extends SQLiteOpenHelper {
    public MyOpenHelper( Context context) {
        //通过传入参数,可以定义数据库名,版本号.在这里直接写死
        super(context,"Account.db",null,1);
    }

    //表结构的初始化
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table info (id integer primary key autoincrement,name varchar(20),money varchar(20))");
        //写死
        db.execSQL("insert into info (name,money)values(‘张三‘,‘2000‘)");
        db.execSQL("insert into info (name,money)values(‘李四‘,‘5000‘)");
        //不写死
        db.execSQL("insert into info (name,money)values(?,?)",new String[]{"小狗","666"});

    }

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

    }
}

 

二.创建sqlitedatabase数据库

import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        SQLiteOpenHelper myOpenHelper=new MyOpenHelper(getApplicationContext());
        SQLiteDatabase database=myOpenHelper.getReadableDatabase();
        Cursor cursor=database.query("info",null,null,null,null,null,null);

        if (cursor!=null&&cursor.getCount()>0){
            while (cursor.moveToNext()){
                System.out.println(cursor.getString(1));
                System.out.println(cursor.getString(2));
            }
        }
    }
}