Android(安卓)Sqlite数据库中基础的增删改查操作

1.创建一个类MyUserlogDBHelper去继承SQLiteOpenHelper，在该类里面创建表。

package com.example.demo;import android.content.ContentValues;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import androidx.annotation.Nullable;public class MyUserlogDBHelper extends SQLiteOpenHelper {    public MyUserlogDBHelper db;    //对外提供参数，单例模式    private static SQLiteOpenHelper mHelper;    public static synchronized SQLiteOpenHelper getInstance(Context context){        if (mHelper==null){            mHelper=new MyUserlogDBHelper(context,"user_log",null,1);        }        return mHelper;    }    private MyUserlogDBHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);    }    @Override    public void onCreate(SQLiteDatabase db) {        //创建表        String sql="create table user_log (_id integer primary key autoincrement,name text)";        //拿到db执行sql语句即可        db.execSQL(sql);    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {    }}

2.在Activity中写查询，增加，修改，删除数据的操作。

package com.example.demo;import androidx.appcompat.app.AppCompatActivity;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.os.Bundle;import android.util.Log;import android.view.View;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }    public void create(View view) {        SQLiteOpenHelper helper = MyUserlogDBHelper.getInstance(this);        SQLiteDatabase readableDatabase = helper.getReadableDatabase();    }    //查询语句    public void query(View view) {        SQLiteOpenHelper instance = MyUserlogDBHelper.getInstance(this);        SQLiteDatabase db = instance.getReadableDatabase();        if (db.isOpen()){            //查询语句            String sql="select * from user_log";            //获取游标            Cursor cursor = db.rawQuery(sql, null);            while(cursor.moveToNext()){                //不规范的写法                /*int _id=cursor.getColumnIndex("0");                int name=cursor.getColumnIndex("1");                */                //规范的写法                int _id=cursor.getInt(cursor.getColumnIndex("_id"));            String name=cursor.getString(cursor.getColumnIndex("name"));                Log.d("数据库", "_id: "+_id+"，name:"+name);            }            //关闭游标            cursor.close();            //关闭数据库            db.close();        }    }    //插入语句    public void insert(View view) {        SQLiteOpenHelper instance = MyUserlogDBHelper.getInstance(this);        SQLiteDatabase db = instance.getWritableDatabase();        //判断数据库是否开启        if (db.isOpen()){            String sql="insert into user_log(name) values('路宇')";            db.execSQL(sql);        }        db.close();    }    //修改    public void update(View view) {        SQLiteOpenHelper instance = MyUserlogDBHelper.getInstance(this);        SQLiteDatabase db = instance.getWritableDatabase();        if (db.isOpen()){            String sql="update user_log set name=? where _id=?";            db.execSQL(sql,new Object[]{"成龙","5"});        }        //关闭数据库        db.close();    }    //删除数据    public void delete(View view) {        SQLiteOpenHelper instance = MyUserlogDBHelper.getInstance(this);        SQLiteDatabase db = instance.getWritableDatabase();        //判断数据是否是打开状态        if (db.isOpen()){            String sql="delete from user_log where _id=?";            db.execSQL(sql,new Object[]{6});        }    }}

3.布局文件。

<?xml version="1.0" encoding="utf-8"?>

以上就是SQLite数据库中，最简单的增删改查操作，想深入学习SQLite在项目中的实际应用，请持续关注后面博文！

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