安卓room框架使用

1.gradle中导入依赖

2.编写实体类

package com.example.chapter06.entity;

import androidx.room.Entity;
import androidx.room.PrimaryKey;
@Entity
public class BookInfo {
    //主键
    @PrimaryKey(autoGenerate=true)
    private int id;

    //姓名
    private String name;
    //作者
    private String author;
    //出版社
    private String press;
    //价格
    private double price;

    public BookInfo(int id, String name, String author, String press, double price) {
        this.id = id;
        this.name = name;
        this.author = author;
        this.press = press;
        this.price = price;
    }

    @Override
    public String toString() {
        return "BookInfo{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", author='" + author + '\'' +
                ", press='" + press + '\'' +
                ", price=" + price +
                '}';
    }

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

    public void setName(String name) {
        this.name = name;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public void setPress(String press) {
        this.press = press;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getAuthor() {
        return author;
    }

    public String getPress() {
        return press;
    }

    public double getPrice() {
        return price;
    }
}

3.写Dao接口

package com.example.chapter06.dao;

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

import com.example.chapter06.entity.BookInfo;

import java.util.List;

@Dao
public interface BookDao {
    //插入
    @Insert
    void insert(BookInfo... book);
    //删除
    @Delete
    void delete(BookInfo... book);
    //删除所有
    @Delete
    void deleteAll();
    //更新
    @Update
    int update(BookInfo... book);
    //查询所有
    @Query("select * from BookInfo")
    List queryAll();
    //根据名称查询
    @Query("select * from BookInfo where name=:name order by id desc limit 1")
    BookInfo queryByName(String name);





}

4.编写Database类 extends RoomDatabase

package com.example.chapter06.database;

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

import com.example.chapter06.dao.BookDao;
import com.example.chapter06.entity.BookInfo;

@Database(entities = {BookInfo.class},version = 1,exportSchema = true)
public abstract class BookDatabase extends RoomDatabase {
    public abstract BookDao bookDao();

}

5.编写myApplication extends Application

package com.example.chapter06;

import android.app.Application;
import android.content.res.Configuration;

import androidx.annotation.NonNull;
import androidx.room.Room;

import com.example.chapter06.dao.BookDao;
import com.example.chapter06.database.BookDatabase;

import java.util.HashMap;

public class MyApplication extends Application {
    private static MyApplication mApp;
    public  HashMap infoMap=new HashMap<>();
    //声明数据库对象
    private  BookDatabase bookDatabase;
    public static MyApplication getInstance()
    {
      return mApp;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        mApp=this;

        bookDatabase= Room.databaseBuilder(this,BookDatabase.class,"book")
                .addMigrations()
                //允许在主线程中操作数据库（Room默认不能在主线程中操作数据库
                .allowMainThreadQueries()
                .build();
    }

    @Override
    public void onTerminate()
    {
        super.onTerminate();
    }

    @Override
    public void onConfigurationChanged(@NonNull Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
    }

    //获取数据库实例
    public BookDatabase getBookDatabase()
    {
        return bookDatabase;
    }
}

6.写界面

7.写java逻辑处理代码

package com.example.chapter06;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;

import com.example.chapter06.dao.BookDao;
import com.example.chapter06.entity.BookInfo;
import com.example.chapter06.util.ToastUtil;

import java.util.List;

public class RoomWriteActivity extends AppCompatActivity implements View.OnClickListener, CompoundButton.OnCheckedChangeListener {
    private EditText et_press;
    private EditText et_name;
    private EditText et_author;
    private EditText et_price;

    private CheckBox cb_marry;
    private Button btn_save;
    private Button btn_delete;
    private Button btn_update;
    private Button btn_query;
    private BookDao bookDao;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_room_write);


        et_press = findViewById(R.id.et_press);
        et_name = findViewById(R.id.et_name);
        et_price = findViewById(R.id.et_price);
        et_author = findViewById(R.id.et_author);

        cb_marry = findViewById(R.id.cb_Marry);
        btn_save = findViewById(R.id.btn_save);
        btn_delete = findViewById(R.id.btn_delete);
        btn_update = findViewById(R.id.btn_update);
        btn_query = findViewById(R.id.btn_query);

        btn_delete.setOnClickListener(this);
        btn_query.setOnClickListener(this);
        btn_update.setOnClickListener(this);
        btn_save.setOnClickListener(this);
        cb_marry.setOnCheckedChangeListener( this);

        bookDao = MyApplication.getInstance().getBookDatabase().bookDao();
        }

    @Override
    public void onClick(View view) {
        String press = et_press.getText().toString();
        String name = et_name.getText().toString();
        String author = et_author.getText().toString();
        String price = et_price.getText().toString();
        switch (view.getId())
        {
            case R.id.btn_save:
                BookInfo b=new BookInfo();
                b.setAuthor(author);
                b.setName(name);
                b.setPress(press);
                b.setPrice(Integer.parseInt(price));
                bookDao.insert(b);
                ToastUtil.show(this,"保存成功");
                break;
            case R.id.btn_query:
                List list=bookDao.queryAll();
                for (BookInfo b1:list)
                {
                    Log.d("ning",b1.toString());
                }
                break;
            case R.id.btn_delete:
                BookInfo b2=new BookInfo();
                b2.setId(1);
                bookDao.delete(b2);
                break;
            case R.id.btn_update:
                BookInfo b4 = bookDao.queryByName(name);
                BookInfo b3 = new BookInfo();
                b3.setId(b4.getId());
                b3.setPrice(Integer.parseInt(price));
                b3.setPress(press);
                b3.setAuthor(author);
                b3.setName(name);
                bookDao.update(b3);
                break;

        }

    }

    @Override
    public void onCheckedChanged(CompoundButton compoundButton, boolean b) {

    }
}