Room数据库操作

Room

注解：对sqlite数据库的封装

导入Room支持：//build.gradle

 

//room
def room_version="2.2.0-alpha01"
implementation "androidx.room:room-runtime:$room_version"  //room Api支持
annotationProcessor "androidx.room:room-compiler:$room_version" //room的注解处理器

Room 三大角色

1. Entity

   package com.neostra.anyan.test;
   ​
   import androidx.annotation.NonNull;
   import androidx.room.Entity;
   import androidx.room.PrimaryKey;
   ​
   @Entity//表实体类
   public class Student {
       @PrimaryKey(autoGenerate = true)
       private int _id;
       private String name;
   ​
       public Student() {
       }
   ​
       public int get_id() {
           return _id;
       }
   ​
       public void set_id(int _id) {
           this._id = _id;
       }
   ​
       public String getName() {
           return name;
       }
   ​
       public void setName(String name) {
           this.name = name;
       }
   ​
       @NonNull
       @Override
       public String toString() {
           return super.toString();
       }
   }

2. DAO

package com.neostra.anyan.test;
​
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//实现对Student表的增删改查
public interface StudentDao {
​
    @Insert//增
    void insertStudents(Student ... students);
    @Delete//只支持删除单个数据
    void deleteStudents(Student... students);
    @Query("delete from Student")//删除表中所有数据
    void deleteAllStudents(Student... students);
    @Update//更新
    void upadateStudents(Student... students);
    @Query("select * from student order by _id asc")//按序查询，返回list
    List<Student> getAllStudents();
}

3. Database

   package com.neostra.anyan.test;
   ​
   import android.content.Context;
   ​
   import androidx.room.Database;
   import androidx.room.Room;
   import androidx.room.RoomDatabase;
   //将表和操作表的DAO联系起来
   @Database(entities = {Student.class},version =1,exportSchema = false)
   public abstract class StudentDatabase extends RoomDatabase {
       //单例模式  返回DB
       private static StudentDatabase INSTANCE;
       static synchronized StudentDatabase getINSTANCE(Context context){
           if (INSTANCE==null){
               INSTANCE= Room.databaseBuilder(context.getApplicationContext(),StudentDatabase.class,"student_database")
                       /*如果数据库默认是异步线程,强制开启主线程操作数据库，此方法谨慎使用，仅测试过程使用*/
                       .allowMainThreadQueries()
                       .build();
           }
           return INSTANCE;
       }
       //为用户提供操作数据库的DAO，当用户需要操作数据库时只需要操作DAO即可
       public abstract StudentDao getStudentDao();
   }

 

//room
def room_version="2.2.0-alpha01"
implementation "androidx.room:room-runtime:$room_version"  //room Api支持
annotationProcessor "androidx.room:room-compiler:$room_version" //room的注解处理器