Android Room数据库的基本使用示例详解

//数据库创建成功,会有类似以下目录,以自己的为准\build\generated\source\kapt\release\com\xxx\xxx\drive\database\appdatabase_impl
    def room_version = "2.5.1"
    kapt "androidx.room:room-compiler:$room_version"
    implementation "androidx.room:room-runtime:$room_version"
    implementation "androidx.room:room-ktx:$room_version"
//这里注意：如果是某一个moudle中要使用room数据库,建议直接将库集成到moudle中的build.gradle中，博主这里遇到将root相关库集成到基类的build.gradle中,一直报错，提示生成数据库失败,上面的appdatabase_impl文件无法生成

/**
 * @description : localuploadrecord 数据库实体类,根据项目需求,定义自己的字段即可
 */
import androidx.room.columninfo
import androidx.room.entity
import androidx.room.primarykey
@entity(tablename = "upload_records")
data class localuploadrecord(
    @primarykey(autogenerate = true)
    val id: int? = null,
    @columninfo(name = "phone_id")
    val phoneid: string,//云机id
    @columninfo(name = "phone_biz_id")
    val phonebizid: string,//云机业务id
    @columninfo(name = "user_id", index = true)
    val userid: string,//登录返回的用户id
    @columninfo(name = "file_name")
    val filename: string,//文件名（含后缀）
    @columninfo(name = "file_path")
    val filepath: string,//文件路径
    @columninfo(name = "phone_name")
    val phonename: string,//云机名称
    @columninfo(name = "file_status")
    var filestatus: filestatus,//waiting, uploading, success, failed,installing,install_fail,install_success
    @columninfo(name = "file_time")
    val filetime: long,//文件操作时间-时间戳:毫秒
    @columninfo(name = "file_size")
    val filesize: long = 0,//文件大小,字节
    @columninfo(name = "err_message")
    var errmessage: string = "",
    @columninfo(name = "reserved_field1")
    var reservedfield1: string = "",//预留字段1
    @columninfo(name = "reserved_field2")
    var reservedfield2: string = "",//预留字段2
    @columninfo(name = "reserved_field3")
    var reservedfield3: string = "",//预留字段3
)

/**
 * @description : uploadrecorddao 创建数据访问对象（dao）
 * @dao：标记这是一个数据访问对象接口
 * @insert、@update、@delete：由room 提供的便捷注解，可以自动生成对应 sql
 * @query：自定义 sql 查询，:参数名表示方法参数
 */
import androidx.room.dao
import androidx.room.delete
import androidx.room.insert
import androidx.room.query
import androidx.room.update
import kotlinx.coroutines.flow.flow
@dao
interface uploadrecorddao {
    /**
     * 插入一条数据
     */
    @insert
    fun insert(record: localuploadrecord): long
    /**
     * 删除最老的数据（按时间戳升序）
     */
    @query("delete from upload_records where id in (select id from upload_records where user_id = :userid order by file_time asc limit :count)")
    fun deleteoldest(userid: string,count:int)
    /**
     * 删除一条记录
     */
    @delete
     fun delete(record: localuploadrecord)
    /**
     * 更新一条记录
     */
    @update
    fun update(record: localuploadrecord)
    /**
     * 根据userid获取所有记录
     */
    @query("select * from upload_records where user_id = :userid order by file_time desc")
    fun getrecordsbyuser(userid: string): flow<list<localuploadrecord>>
    /**
     * 根据userid和filestatus获取记录
     */
    @query("select * from upload_records where user_id = :userid and file_status in (:statuslist) order by file_time desc")
    fun getrecordsbyuser(userid: string,statuslist: list<filestatus>):list<localuploadrecord>
    /**
     * 分页获取记录
     */
    @query("select * from upload_records where user_id = :userid order by file_time desc limit :pagesize offset :offset")
    fun getrecordsbyuserpaged(userid: string, pagesize: int, offset: int): list<localuploadrecord>
    /**
     * 根据userid查询记录数
     */
    @query("select count(*) from upload_records where user_id = :userid")
    fun getrecordcountbyuser(userid: string): int
    /**
     * 根据id查询一条记录
     */
    @query("select * from upload_records where id = :id")
//    suspend fun getrecordbyid(id: long): uploadrecord 低版本在dao中不能加suspend关键字，会报错,2.6.1中不会
    fun getrecordbyid(id: long): localuploadrecord
    /**
     * 删除用户的所有数据
     */
    @query("delete from upload_records where user_id = :userid")
     fun deleteallbyuserid(userid: string): int
    /**
     * 根据id 批量删除数据
     */
    @query("delete from upload_records where id in (:ids)")
     fun deletebyids(ids: list<long>): int
}

/**
 * @description : uploaddatabase 创建数据库类
 * @database(entities = {myuser.class}, version = 1)：标记数据库类，指定包含的表和版本号
 * migration：定义数据库版本迁移逻辑
 * 关于数据库迁移：
 * 数据库迁移的核心作用是在修改数据库结构后（比如在实体类中添加新字段或是在库中添加新表），安全、无损地将旧版本数据库升级到新版本，同时保留用户的原有数据。
 * 版本迁移逻辑：必须增加数据库的版本号，并提供一个migration对象来告诉room如何从旧版本正确迁移到新版本。
 */
import android.content.context
import androidx.room.database
import androidx.room.room
import androidx.room.roomdatabase
@database(
    entities = [localuploadrecord::class],
    version = 1,
    exportschema = false
)
abstract class uploaddatabase : roomdatabase() {
    abstract fun uploadrecorddao(): uploadrecorddao
    companion object {
        @volatile
        private var instance: uploaddatabase? = null
        fun getinstance(context: context): uploaddatabase {
            return instance ?: synchronized(this) {
                val instance = room.databasebuilder(
                    context.applicationcontext,
                    uploaddatabase::class.java,
                    "upload_database"
                ).build()
                instance = instance
                instance
            }
        }
    }
}

import android.content.context
import android.util.log
import com.android.base.kits.klog
import com.yixin.cloudphone.drive.data.bean.pagedresult
import com.yixin.cloudphone.drive.util.constant
import kotlinx.coroutines.flow.flow
/**
 * @description : uploaddatabasemanager
 */
class uploaddatabasemanager(private val context: context) {
    //每个用户最大存储上传记录个数
    private val record_limit_count=1000
    private val database: uploaddatabase by lazy {
        uploaddatabase.getinstance(context)
    }
    private val dao: uploadrecorddao by lazy {
        database.uploadrecorddao()
    }
    /**
     * 新增记录
     * 每个用户id最多1000条数据,超过的要删除掉
     */
     fun insertuploadrecord(record: localuploadrecord): long {
            val id=dao.insert(record)
            val count=dao.getrecordcountbyuser(record.userid)
            if (count>record_limit_count){
                // 删除超过1000条的最老记录
                val deletecount=count-record_limit_count
                if(deletecount>0){
                    dao.deleteoldest(record.userid,deletecount)
                    klog.d(constant.tag,"insertuploadrecord deleteoldest,sumsize:$count, deletecount:$deletecount")
                }
            }
            return id
    }
    //更新上传记录
     fun updateuploadrecord(record: localuploadrecord) {
        dao.update(record)
    }
    // 获取用户的所有上传记录（flow版本，用于观察数据变化）
    fun getuploadrecordsbyuser(userid: string): flow<list<localuploadrecord>> {
        return dao.getrecordsbyuser(userid)
    }
    // 根据userid和filestatus获取记录
    fun getuploadrecordsbyuser(userid: string,statuslist: list<filestatus>): list<localuploadrecord>{
        return dao.getrecordsbyuser(userid,statuslist)
    }
    // 分页获取用户的上传记录
    suspend fun getuploadrecordspaged(
        userid: string,
        page: int,
        pagesize: int = 20
    ): pagedresult<localuploadrecord> {
        val offset = (page - 1) * pagesize
        val records = dao.getrecordsbyuserpaged(userid, pagesize, offset)
        val totalcount = dao.getrecordcountbyuser(userid)
        val totalpages = (totalcount + pagesize - 1) / pagesize
        return pagedresult(
            data = records,
            currentpage = page,
            pagesize = pagesize,
            totalcount = totalcount,
            totalpages = totalpages
        )
    }
    // 根据id获取记录
     fun getrecordbyid(id: long): localuploadrecord? {
        return dao.getrecordbyid(id)
    }
}

//在activity或viewmoudle中使用数据库
private val roommanager: uploaddatabasemanager by lazy {
        uploaddatabasemanager(vcapplication.getinstance())
    }
//查询数据库数据,使用时应该在线程中调用,数据库操作属于耗时操作
    viewmodelscope.launch(dispatchers.io) {
    val filelist=roommanager.getuploadrecordsbyuser(userid)
   }