[移动开发] Android Room框架使用

开发: C++知识库 Java知识库 JavaScript Python PHP知识库人工智能区块链大数据移动开发嵌入式开发工具数据结构与算法开发测试游戏开发网络协议系统运维
教程: HTML教程 CSS教程 JavaScript教程 Go语言教程 JQuery教程 VUE教程 VUE3教程 Bootstrap教程 SQL数据库教程 C语言教程 C++教程 Java教程 Python教程 Python3教程 C#教程
数码: 电脑笔记本显卡显示器固态硬盘硬盘耳机手机 iphone vivo oppo 小米华为单反装机图拉丁

-> 移动开发 -> Android Room框架使用 -> 正文阅读

[移动开发]Android Room框架使用

Room 的使用三角色介绍：

使用步骤：

使用准备：

使用：?

Room 的使用三角色介绍：

@Entity(数据库表? 与? 类相似);
@Dao (操作引擎，用于操作数据库)
@Database(创建数据库)

使用步骤：

使用准备：

导入依赖：（在 bulid.gradle 文件）中导入，（导入的本处版本只是举例，可在官网出查找其他版本）

dependencies {

    def room_version = "2.4.2"

    implementation "androidx.room:room-runtime:$room_version"
    annotationProcessor "androidx.room:room-compiler:$room_version"
}

结合Rxjava使用额外添加相关依赖：

 dependencies {
    ...
   // optional - RxJava2 support for Room
    implementation "androidx.room:room-rxjava2:$room_version"

    // optional - RxJava3 support for Room
    implementation "androidx.room:room-rxjava3:$room_version"

    // optional - Guava support for Room, including Optional and ListenableFuture
    implementation "androidx.room:room-guava:$room_version"

    // optional - Test helpers
    testImplementation "androidx.room:room-testing:$room_version"

    // optional - Paging 3 Integration
    implementation "androidx.room:room-paging:2.5.0-alpha01"
}

使用：?

@Entity? 创建数据库表（与类对象相似）：? ??

package com.example.androidapp.SQlist;

import androidx.room.Entity;
import androidx.room.PrimaryKey;

@Entity(tableName = "Agency")
public class Agency implements Serializable {
    @PrimaryKey(autoGenerate = true)
    private int id;
    private String agency_name;
    private String agency_nowTime;
    private String agency_futureTime;


    private String agency_okTime;
    private String agency_type;
    private String agency_nowstate;
    private String agency_context;

    public Agency(String agency_name, String agency_nowTime, String agency_futureTime,
         
    String agency_type, String agency_nowstate, String agency_context) {
        this.agency_name = agency_name;
        this.agency_nowTime = agency_nowTime;
        this.agency_futureTime = agency_futureTime;
        this.agency_type = agency_type;
        this.agency_nowstate = agency_nowstate;
        this.agency_context = agency_context;
    } 
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getAgency_name() {
        return agency_name;
    }

    public void setAgency_name(String agency_name) {
        this.agency_name = agency_name;
    }

    public String getAgency_nowTime() {
        return agency_nowTime;
    }

    public void setAgency_nowTime(String agency_nowTime) {
        this.agency_nowTime = agency_nowTime;
    }

    public String getAgency_futureTime() {
        return agency_futureTime;
    }

    public void setAgency_futureTime(String agency_futureTime) {
        this.agency_futureTime = agency_futureTime;
    }

    public String getAgency_type() {
        return agency_type;
    }

    public void setAgency_type(String agency_type) {
        this.agency_type = agency_type;
    }

    public String getAgency_nowstate() {
        return agency_nowstate;
    }

    public void setAgency_nowstate(String agency_nowstate) {
        this.agency_nowstate = agency_nowstate;
    }

    public String getAgency_context() {
        return agency_context;
    }

    public void setAgency_context(String agency_context) {
        this.agency_context = agency_context;
    }

    public String getAgency_okTime() {
        return agency_okTime;
    }

    public void setAgency_okTime(String agency_okTime) {
        this.agency_okTime = agency_okTime;
    }

    @Override
    public String toString() {
        return "Agency{" +
                "id=" + id +
                ", agency_name='" + agency_name + '\'' +
                ", agency_nowTime='" + agency_nowTime + '\'' +
                ", agency_futureTime='" + agency_futureTime + '\'' +
                ", agency_type='" + agency_type + '\'' +
                ", agency_nowstate='" + agency_nowstate + '\'' +
                ", agency_context='" + agency_context + '\'' +
                '}';
    }
}

@Dao 操作数据库

package com.example.androidapp.SQlist;

import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.Query;
import androidx.room.Update;

import java.util.List;
@Dao
public interface AgencyDao {

    @Insert
    void insertAgencies(Agency... agencies);

    @Update
    void updateAgencies(Agency... agencies);

    @Delete
    void deleteAgencies(Agency... agencies);

    @Query("SELECT * FROM Agency ORDER BY ID DESC")
    List<Agency> getAllAgency();
}

@Database 创建数据库并与数据表关联：暴露Dao给用户操作数据库

package com.example.androidapp.SQlist;

import android.content.Context;

import androidx.room.Database;
import androidx.room.Room;
import androidx.room.RoomDatabase;

//数据库 关联 之前的表 数据库信息
//,User.class
@Database(entities = {Agency.class},version = 1,exportSchema = false)
public abstract class AgencyDatabase extends RoomDatabase {

//    暴露 dao 给用户操作 数据库
    public abstract AgencyDao getAgencyDao();

//    单例模式 返回 db
    private static AgencyDatabase INSTANCE;
    static synchronized AgencyDatabase getInstance(Context context){
        if (INSTANCE == null){
            INSTANCE = Room.databaseBuilder(context.getApplicationContext(),AgencyDatabase.class,"Agency_database")
                    .build();
        }
        return INSTANCE;
    }
}

创建一个 DBclass 用于实现在异步操作中进行数据操作（这里我用了AsyncTask进行异步操作）

package com.example.androidapp.SQlist;

import android.content.Context;
import android.os.AsyncTask;

import java.util.ArrayList;
import java.util.List;

public class DBEngine {

    //    接收 传入的 AgencyDao 对象
    private AgencyDao agencyDao;
    //    接收 传入的 UserDao 对象
    private UserDao userDao;


    //    接收 获取的所有数据 实现单例
    private static List<Agency> allAgencies = new ArrayList<>();
    private static List<User> allUsers = new ArrayList<>();

    //    实现 构造方法
    public DBEngine(Context context) {
        AgencyDatabase agencyDatabase = AgencyDatabase.getInstance(context);
        agencyDao = agencyDatabase.getAgencyDao();
        UserDatabase userDatabase = UserDatabase.getInstance(context);
        userDao = userDatabase.getUserDao();
    }

    ;

//*********************************************************************************************

    //    插入 操作
    public void insertAgencies(Agency... agencies) {
//        开启 InsertAsyncTask 线程
        new InsertAsyncTask(agencyDao).execute(agencies);
    }
    //    更新 操作
    public void updateAgencies(Agency... agencies) {
        new UpdateAsyncTask(agencyDao).execute(agencies);
    }
    //    删除 操作
    public void deleteAgencies(Agency... agencies) {
        new DeleteAsyncTask(agencyDao).execute(agencies);
    }
    //    获取 操作
    public void getAllAgencies(Agency... agencies) {
        new GetAllAgencies(agencyDao).execute();
    }
//*********************************************************************************************
//Agency
    //    实现 插入功能
    private static class InsertAsyncTask extends AsyncTask<Agency, Void, Void> {

        //        获取 AgencyDao 对象
        private AgencyDao dao;

        //        实现 构造方法
        public InsertAsyncTask(AgencyDao agencyDao) {
            dao = agencyDao;
        }

        //        实现 AgencyDao 操作
        @Override
        protected Void doInBackground(Agency... agencies) {
            dao.insertAgencies(agencies);
            return null;
        }
    }
    //    实现 更新功能
    private static class UpdateAsyncTask extends AsyncTask<Agency, Void, Void> {

        private AgencyDao dao;

        public UpdateAsyncTask(AgencyDao agencyDao) {
            dao = agencyDao;
        }

        @Override
        protected Void doInBackground(Agency... agencies) {
            dao.updateAgencies(agencies);
            return null;
        }
    }
    //    实现 删除功能
    private static class DeleteAsyncTask extends AsyncTask<Agency, Void, Void> {
        private AgencyDao dao;

        public DeleteAsyncTask(AgencyDao agencyDao) {
            dao = agencyDao;
        }

        @Override
        protected Void doInBackground(Agency... agencies) {
            dao.deleteAgencies(agencies);
            return null;
        }
    }
    //    实现 获取所有数据 功能
    private static class GetAllAgencies extends AsyncTask<Void, Void, List<Agency>> {

        private AgencyDao dao;

        public GetAllAgencies(AgencyDao agencyDao) {
            dao = agencyDao;
        }
        //        获取数据
        @Override
        protected List<Agency> doInBackground(Void... voids) {
            allAgencies = dao.getAllAgency();
            return allAgencies;
        }
        //        返回 数据
        @Override
        protected void onPostExecute(List<Agency> agencies) {
            super.onPostExecute(agencies);
            allAgencies = agencies;
        }
    }

在主类中实例化一个DB?对象，都数据进行操作

    //        获取 数据库引擎
    private DBEngine dbEngine;

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

        dbEngine = new DBEngine(this);

        dbEngine.getAllAgencies();

//      实例化 一个 Agency 对象
        Agency new_agency = new Agency(name, nowTimeStr, futureTimeStr, typeStr, stateStr, contextStr);


    //    插入 操作
        dbEngine.insertAgencies(new_agency );
    //    更新 操作
        dbEngine.updateAgencies(new_agency );
    //    删除 操作
        dbEngine.deleteAgencies(new_agency );
    //    获取 操作
        dbEngine.getAllAgencies(new_agency );
   
    }

? ? ? ? 项目案例：